diff --git a/docs/generators/ada-server.md b/docs/generators/ada-server.md
index 9a86032ec7e6..7f804ddf0dff 100644
--- a/docs/generators/ada-server.md
+++ b/docs/generators/ada-server.md
@@ -7,6 +7,16 @@ sidebar_label: ada-server
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |projectName|GNAT project name| |defaultProject|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/ada.md b/docs/generators/ada.md
index 2b382b4c4fc2..c5d73461dc2a 100644
--- a/docs/generators/ada.md
+++ b/docs/generators/ada.md
@@ -7,6 +7,16 @@ sidebar_label: ada
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |projectName|GNAT project name| |defaultProject|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/android.md b/docs/generators/android.md
index 4eeeec214b62..430500d9e6a4 100644
--- a/docs/generators/android.md
+++ b/docs/generators/android.md
@@ -15,6 +15,16 @@ sidebar_label: android
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |groupId|groupId for use in the generated build.gradle and pom.xml| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template) to use|<dl><dt>**volley**</dt><dd>HTTP client: Volley 1.0.19 (default)</dd><dt>**httpclient**</dt><dd>HTTP client: Apache HttpClient 4.3.6. JSON processing: Gson 2.3.1. IMPORTANT: Android client using HttpClient is not actively maintained and will be depecreated in the next major release.</dd></dl>|null|
 |modelPackage|package for generated models| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/apache2.md b/docs/generators/apache2.md
index cfa9756c7d58..8b92e02dd19f 100644
--- a/docs/generators/apache2.md
+++ b/docs/generators/apache2.md
@@ -7,6 +7,16 @@ sidebar_label: apache2
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/apex.md b/docs/generators/apex.md
index 06c54e3b9722..80ac5bd24fba 100644
--- a/docs/generators/apex.md
+++ b/docs/generators/apex.md
@@ -10,6 +10,16 @@ sidebar_label: apex
 |buildMethod|The build method for this package.| |null|
 |classPrefix|Prefix for generated classes. Set this to avoid overwriting existing classes in your org.| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |namedCredential|The named credential name for the HTTP callouts| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/asciidoc.md b/docs/generators/asciidoc.md
index 66a175518bc9..777a62080c7b 100644
--- a/docs/generators/asciidoc.md
+++ b/docs/generators/asciidoc.md
@@ -16,6 +16,16 @@ sidebar_label: asciidoc
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/avro-schema.md b/docs/generators/avro-schema.md
index 13ca849949a9..6f0621b74774 100644
--- a/docs/generators/avro-schema.md
+++ b/docs/generators/avro-schema.md
@@ -7,6 +7,16 @@ sidebar_label: avro-schema
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|package for generated classes (where supported)| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/bash.md b/docs/generators/bash.md
index b91eb990a6d9..3d626eff7209 100644
--- a/docs/generators/bash.md
+++ b/docs/generators/bash.md
@@ -13,6 +13,16 @@ sidebar_label: bash
 |generateBashCompletion|Whether to generate the Bash completion script| |false|
 |generateZshCompletion|Whether to generate the Zsh completion script| |false|
 |hostEnvironmentVariable|Name of environment variable where host can be defined (e.g. PETSTORE_HOST='http://api.openapitools.org:8080')| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |processMarkdown|Convert all Markdown Markup into terminal formatting| |false|
 |scriptName|The name of the script that will be generated (e.g. petstore-cli)| |null|
diff --git a/docs/generators/c.md b/docs/generators/c.md
index ee9b2586696e..8ebc3221faee 100644
--- a/docs/generators/c.md
+++ b/docs/generators/c.md
@@ -8,6 +8,16 @@ sidebar_label: c
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/clojure.md b/docs/generators/clojure.md
index b2f3a6a4d912..e42936d9f86c 100644
--- a/docs/generators/clojure.md
+++ b/docs/generators/clojure.md
@@ -8,6 +8,16 @@ sidebar_label: clojure
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |baseNamespace|the base/top namespace (Default: generated from projectName)| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |projectDescription|description of the project (Default: using info.description or &quot;Client library of &lt;projectName&gt;&quot;)| |null|
 |projectLicenseName|name of the license the project uses (Default: using info.license.name or not included in project.clj)| |null|
diff --git a/docs/generators/cpp-qt5-client.md b/docs/generators/cpp-qt5-client.md
index bc55db14523d..9a043e53237e 100644
--- a/docs/generators/cpp-qt5-client.md
+++ b/docs/generators/cpp-qt5-client.md
@@ -9,6 +9,16 @@ sidebar_label: cpp-qt5-client
 |contentCompression|Enable Compressed Content Encoding for requests and responses| |false|
 |cppNamespace|C++ namespace (convention: name::space::for::api).| |OpenAPI|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelNamePrefix|Prefix that will be prepended to all model names.| |OAI|
 |optionalProjectFile|Generate client.pri.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/cpp-qt5-qhttpengine-server.md b/docs/generators/cpp-qt5-qhttpengine-server.md
index 2b2cd4e9f15f..574a019f13be 100644
--- a/docs/generators/cpp-qt5-qhttpengine-server.md
+++ b/docs/generators/cpp-qt5-qhttpengine-server.md
@@ -9,6 +9,16 @@ sidebar_label: cpp-qt5-qhttpengine-server
 |contentCompression|Enable Compressed Content Encoding for requests and responses| |false|
 |cppNamespace|C++ namespace (convention: name::space::for::api).| |OpenAPI|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelNamePrefix|Prefix that will be prepended to all model names.| |OAI|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |reservedWordPrefix|Prefix to prepend to reserved words in order to avoid conflicts| |r_|
diff --git a/docs/generators/cpp-tizen.md b/docs/generators/cpp-tizen.md
index f805721b5770..16022f8f5370 100644
--- a/docs/generators/cpp-tizen.md
+++ b/docs/generators/cpp-tizen.md
@@ -7,6 +7,16 @@ sidebar_label: cpp-tizen
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |reservedWordPrefix|Prefix to prepend to reserved words in order to avoid conflicts| |r_|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/cwiki.md b/docs/generators/cwiki.md
index f2d5342f8f36..bf7949015bd0 100644
--- a/docs/generators/cwiki.md
+++ b/docs/generators/cwiki.md
@@ -15,6 +15,16 @@ sidebar_label: cwiki
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/dart-dio.md b/docs/generators/dart-dio.md
index 05514b9a1e4e..fd16331b9a15 100644
--- a/docs/generators/dart-dio.md
+++ b/docs/generators/dart-dio.md
@@ -9,6 +9,16 @@ sidebar_label: dart-dio
 |browserClient|Is the client browser based (for Dart 1.x only)| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**core**</dt><dd>Dart core library (DateTime)</dd><dt>**timemachine**</dt><dd>Time Machine is date and time library for Flutter, Web, and Server with support for timezones, calendars, cultures, formatting and parsing.</dd></dl>|core|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |nullableFields|Is the null fields should be in the JSON payload| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |pubAuthor|Author name in generated pubspec| |null|
diff --git a/docs/generators/dart-jaguar.md b/docs/generators/dart-jaguar.md
index 5e81f82025f3..995676b9a134 100644
--- a/docs/generators/dart-jaguar.md
+++ b/docs/generators/dart-jaguar.md
@@ -8,6 +8,16 @@ sidebar_label: dart-jaguar
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |browserClient|Is the client browser based (for Dart 1.x only)| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |nullableFields|Is the null fields should be in the JSON payload| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |pubAuthor|Author name in generated pubspec| |null|
diff --git a/docs/generators/dart.md b/docs/generators/dart.md
index 993c31cf4477..7cad220b66ea 100644
--- a/docs/generators/dart.md
+++ b/docs/generators/dart.md
@@ -8,6 +8,16 @@ sidebar_label: dart
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |browserClient|Is the client browser based (for Dart 1.x only)| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |pubAuthor|Author name in generated pubspec| |null|
 |pubAuthorEmail|Email address of the author in generated pubspec| |null|
diff --git a/docs/generators/dynamic-html.md b/docs/generators/dynamic-html.md
index b252e414bdc8..6d120dd987bd 100644
--- a/docs/generators/dynamic-html.md
+++ b/docs/generators/dynamic-html.md
@@ -11,6 +11,16 @@ sidebar_label: dynamic-html
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |groupId|groupId in generated pom.xml| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/elixir.md b/docs/generators/elixir.md
index 14afa95bc9fd..9dc1c27d1893 100644
--- a/docs/generators/elixir.md
+++ b/docs/generators/elixir.md
@@ -8,6 +8,16 @@ sidebar_label: elixir
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay.Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseHeader|The license header to prepend to the top of all source files.| |null|
 |packageName|Elixir package name (convention: lowercase).| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/fsharp-functions.md b/docs/generators/fsharp-functions.md
index a7e28602b33e..456a7daaa424 100644
--- a/docs/generators/fsharp-functions.md
+++ b/docs/generators/fsharp-functions.md
@@ -7,6 +7,16 @@ sidebar_label: fsharp-functions
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |NoLicense|
 |licenseUrl|The URL of the license| |http://localhost|
 |packageAuthors|Specifies Authors property in the .NET Core project file.| |OpenAPI|
diff --git a/docs/generators/groovy.md b/docs/generators/groovy.md
index 32699d5a12c1..dbdec2603134 100644
--- a/docs/generators/groovy.md
+++ b/docs/generators/groovy.md
@@ -25,6 +25,16 @@ sidebar_label: groovy
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/haskell-http-client.md b/docs/generators/haskell-http-client.md
index 41163e8fa883..9b9a848ae683 100644
--- a/docs/generators/haskell-http-client.md
+++ b/docs/generators/haskell-http-client.md
@@ -24,6 +24,16 @@ sidebar_label: haskell-http-client
 |generateModelConstructors|Generate smart constructors (only supply required fields) for models| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |inlineMimeTypes|Inline (hardcode) the content-type and accept parameters on operations, when there is only 1 option| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelDeriving|Additional classes to include in the deriving() clause of Models| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |requestType|Set the name of the type used to generate requests| |null|
diff --git a/docs/generators/haskell.md b/docs/generators/haskell.md
index 2e35a073d890..6bb19ea0f864 100644
--- a/docs/generators/haskell.md
+++ b/docs/generators/haskell.md
@@ -8,6 +8,16 @@ sidebar_label: haskell
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |apiPackage|package for generated api classes| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |serveStatic|serve will serve files from the directory 'static'.| |true|
diff --git a/docs/generators/html.md b/docs/generators/html.md
index 78cef65b33b9..dd8c9fa9d651 100644
--- a/docs/generators/html.md
+++ b/docs/generators/html.md
@@ -15,6 +15,16 @@ sidebar_label: html
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/html2.md b/docs/generators/html2.md
index 51d39c72a7d4..7201bdc24963 100644
--- a/docs/generators/html2.md
+++ b/docs/generators/html2.md
@@ -15,6 +15,16 @@ sidebar_label: html2
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |packageName|C# package name| |null|
diff --git a/docs/generators/java-inflector.md b/docs/generators/java-inflector.md
index f34df4d7a136..4d9c6bfe7e4a 100644
--- a/docs/generators/java-inflector.md
+++ b/docs/generators/java-inflector.md
@@ -27,6 +27,16 @@ sidebar_label: java-inflector
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.controllers|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/java-msf4j.md b/docs/generators/java-msf4j.md
index 27017264e1c8..bedc76b14d88 100644
--- a/docs/generators/java-msf4j.md
+++ b/docs/generators/java-msf4j.md
@@ -28,6 +28,16 @@ sidebar_label: java-msf4j
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**jersey1**</dt><dd>Jersey core 1.x</dd><dt>**jersey2**</dt><dd>Jersey core 2.x</dd></dl>|jersey2|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/java-pkmst.md b/docs/generators/java-pkmst.md
index c8df6eb88723..95b92bbb1116 100644
--- a/docs/generators/java-pkmst.md
+++ b/docs/generators/java-pkmst.md
@@ -29,6 +29,16 @@ sidebar_label: java-pkmst
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |com.prokarma.pkmst.controller|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |com.prokarma.pkmst.model|
diff --git a/docs/generators/java-play-framework.md b/docs/generators/java-play-framework.md
index 3066a14a7224..6801838e4a48 100644
--- a/docs/generators/java-play-framework.md
+++ b/docs/generators/java-play-framework.md
@@ -31,6 +31,16 @@ sidebar_label: java-play-framework
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |apimodels|
diff --git a/docs/generators/java-undertow-server.md b/docs/generators/java-undertow-server.md
index 34544a236c38..94bf4e39cc1a 100644
--- a/docs/generators/java-undertow-server.md
+++ b/docs/generators/java-undertow-server.md
@@ -27,6 +27,16 @@ sidebar_label: java-undertow-server
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.handler|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |null|
diff --git a/docs/generators/java-vertx-web.md b/docs/generators/java-vertx-web.md
index cd6c3ee4e9e6..a3fff5103861 100644
--- a/docs/generators/java-vertx-web.md
+++ b/docs/generators/java-vertx-web.md
@@ -27,6 +27,16 @@ sidebar_label: java-vertx-web
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.vertxweb.server|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.vertxweb.server.model|
diff --git a/docs/generators/java-vertx.md b/docs/generators/java-vertx.md
index 58c68915ade5..13e7bb94c420 100644
--- a/docs/generators/java-vertx.md
+++ b/docs/generators/java-vertx.md
@@ -27,6 +27,16 @@ sidebar_label: java-vertx
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.server.api.model|
diff --git a/docs/generators/java.md b/docs/generators/java.md
index 8cdcd9dc4e3d..289ad4405093 100644
--- a/docs/generators/java.md
+++ b/docs/generators/java.md
@@ -29,6 +29,16 @@ sidebar_label: java
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.client|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template) to use|<dl><dt>**jersey1**</dt><dd>HTTP client: Jersey client 1.19.x. JSON processing: Jackson 2.9.x. Enable Java6 support using '-DsupportJava6=true'. Enable gzip request encoding using '-DuseGzipFeature=true'. IMPORTANT NOTE: jersey 1.x is no longer actively maintained so please upgrade to 'jersey2' or other HTTP libaries instead.</dd><dt>**jersey2**</dt><dd>HTTP client: Jersey client 2.25.1. JSON processing: Jackson 2.9.x</dd><dt>**jersey2-experimental**</dt><dd>HTTP client: Jersey client 2.25.1. JSON processing: Jackson 2.9.x</dd><dt>**feign**</dt><dd>HTTP client: OpenFeign 9.x (deprecated) or 10.x (default). JSON processing: Jackson 2.9.x.</dd><dt>**okhttp-gson**</dt><dd>[DEFAULT] HTTP client: OkHttp 3.x. JSON processing: Gson 2.8.x. Enable Parcelable models on Android using '-DparcelableModel=true'. Enable gzip request encoding using '-DuseGzipFeature=true'.</dd><dt>**retrofit**</dt><dd>HTTP client: OkHttp 2.x. JSON processing: Gson 2.x (Retrofit 1.9.0). IMPORTANT NOTE: retrofit1.x is no longer actively maintained so please upgrade to 'retrofit2' instead.</dd><dt>**retrofit2**</dt><dd>HTTP client: OkHttp 3.x. JSON processing: Gson 2.x (Retrofit 2.3.0). Enable the RxJava adapter using '-DuseRxJava[2]=true'. (RxJava 1.x or 2.x)</dd><dt>**resttemplate**</dt><dd>HTTP client: Spring RestTemplate 4.x. JSON processing: Jackson 2.9.x</dd><dt>**webclient**</dt><dd>HTTP client: Spring WebClient 5.x. JSON processing: Jackson 2.9.x</dd><dt>**resteasy**</dt><dd>HTTP client: Resteasy client 3.x. JSON processing: Jackson 2.9.x</dd><dt>**vertx**</dt><dd>HTTP client: VertX client 3.x. JSON processing: Jackson 2.9.x</dd><dt>**google-api-client**</dt><dd>HTTP client: Google API client 1.x. JSON processing: Jackson 2.9.x</dd><dt>**rest-assured**</dt><dd>HTTP client: rest-assured : 4.x. JSON processing: Gson 2.x or Jackson 2.10.x. Only for Java 8</dd><dt>**native**</dt><dd>HTTP client: Java native HttpClient. JSON processing: Jackson 2.9.x. Only for Java11+</dd><dt>**microprofile**</dt><dd>HTTP client: Microprofile client X.x. JSON processing: Jackson 2.9.x</dd></dl>|okhttp-gson|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/javascript-apollo.md b/docs/generators/javascript-apollo.md
index 44cad073fd8d..51a0421dcd72 100644
--- a/docs/generators/javascript-apollo.md
+++ b/docs/generators/javascript-apollo.md
@@ -11,6 +11,16 @@ sidebar_label: javascript-apollo
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|name of the license the project uses (Default: using info.license.name)| |null|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/javascript-closure-angular.md b/docs/generators/javascript-closure-angular.md
index 89b3bd9b0ffe..4cf42f33a9c5 100644
--- a/docs/generators/javascript-closure-angular.md
+++ b/docs/generators/javascript-closure-angular.md
@@ -8,6 +8,16 @@ sidebar_label: javascript-closure-angular
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/javascript-flowtyped.md b/docs/generators/javascript-flowtyped.md
index 6ecd6654d10d..8efe8bba9bed 100644
--- a/docs/generators/javascript-flowtyped.md
+++ b/docs/generators/javascript-flowtyped.md
@@ -9,6 +9,16 @@ sidebar_label: javascript-flowtyped
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/javascript.md b/docs/generators/javascript.md
index 1181fffa500f..139499823d60 100644
--- a/docs/generators/javascript.md
+++ b/docs/generators/javascript.md
@@ -12,6 +12,16 @@ sidebar_label: javascript
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|name of the license the project uses (Default: using info.license.name)| |null|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/jaxrs-cxf-cdi.md b/docs/generators/jaxrs-cxf-cdi.md
index ccd6d823c1e3..13378c214443 100644
--- a/docs/generators/jaxrs-cxf-cdi.md
+++ b/docs/generators/jaxrs-cxf-cdi.md
@@ -31,6 +31,16 @@ sidebar_label: jaxrs-cxf-cdi
 |interfaceOnly|Whether to generate only API interface stubs without the server files.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**&lt;default&gt;**</dt><dd>JAXRS spec only, to be deployed in an app server (TomEE, JBoss, WLS, ...)</dd><dt>**quarkus**</dt><dd>Server using Quarkus</dd><dt>**thorntail**</dt><dd>Server using Thorntail</dd><dt>**openliberty**</dt><dd>Server using Open Liberty</dd><dt>**helidon**</dt><dd>Server using Helidon</dd></dl>|&lt;default&gt;|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/jaxrs-cxf-client.md b/docs/generators/jaxrs-cxf-client.md
index 0d1c841f153d..052caa1f2927 100644
--- a/docs/generators/jaxrs-cxf-client.md
+++ b/docs/generators/jaxrs-cxf-client.md
@@ -27,6 +27,16 @@ sidebar_label: jaxrs-cxf-client
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-cxf-extended.md b/docs/generators/jaxrs-cxf-extended.md
index b83a1d55e4f9..28756d164f85 100644
--- a/docs/generators/jaxrs-cxf-extended.md
+++ b/docs/generators/jaxrs-cxf-extended.md
@@ -34,6 +34,16 @@ sidebar_label: jaxrs-cxf-extended
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |loadTestDataFromFile|Load test data from a generated JSON file| |false|
diff --git a/docs/generators/jaxrs-cxf.md b/docs/generators/jaxrs-cxf.md
index d3dd5e448267..343374b3c249 100644
--- a/docs/generators/jaxrs-cxf.md
+++ b/docs/generators/jaxrs-cxf.md
@@ -33,6 +33,16 @@ sidebar_label: jaxrs-cxf
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-jersey.md b/docs/generators/jaxrs-jersey.md
index 9183a75d65f7..ef5a852acf60 100644
--- a/docs/generators/jaxrs-jersey.md
+++ b/docs/generators/jaxrs-jersey.md
@@ -28,6 +28,16 @@ sidebar_label: jaxrs-jersey
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**jersey1**</dt><dd>Jersey core 1.x</dd><dt>**jersey2**</dt><dd>Jersey core 2.x</dd></dl>|jersey2|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/jaxrs-resteasy-eap.md b/docs/generators/jaxrs-resteasy-eap.md
index 3a7623db6796..1d5f312382e0 100644
--- a/docs/generators/jaxrs-resteasy-eap.md
+++ b/docs/generators/jaxrs-resteasy-eap.md
@@ -29,6 +29,16 @@ sidebar_label: jaxrs-resteasy-eap
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-resteasy.md b/docs/generators/jaxrs-resteasy.md
index 724c15e9289d..60e52043dc4a 100644
--- a/docs/generators/jaxrs-resteasy.md
+++ b/docs/generators/jaxrs-resteasy.md
@@ -29,6 +29,16 @@ sidebar_label: jaxrs-resteasy
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-spec.md b/docs/generators/jaxrs-spec.md
index 3bd0accada9b..98cbb0c96c3b 100644
--- a/docs/generators/jaxrs-spec.md
+++ b/docs/generators/jaxrs-spec.md
@@ -31,6 +31,16 @@ sidebar_label: jaxrs-spec
 |interfaceOnly|Whether to generate only API interface stubs without the server files.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**&lt;default&gt;**</dt><dd>JAXRS spec only, to be deployed in an app server (TomEE, JBoss, WLS, ...)</dd><dt>**quarkus**</dt><dd>Server using Quarkus</dd><dt>**thorntail**</dt><dd>Server using Thorntail</dd><dt>**openliberty**</dt><dd>Server using Open Liberty</dd><dt>**helidon**</dt><dd>Server using Helidon</dd></dl>|&lt;default&gt;|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/jmeter.md b/docs/generators/jmeter.md
index 142f826d7938..e8cbb38e5fd5 100644
--- a/docs/generators/jmeter.md
+++ b/docs/generators/jmeter.md
@@ -7,6 +7,16 @@ sidebar_label: jmeter
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/k6.md b/docs/generators/k6.md
index 4ff51c7527fb..2f6d321b14f4 100644
--- a/docs/generators/k6.md
+++ b/docs/generators/k6.md
@@ -7,6 +7,16 @@ sidebar_label: k6
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/markdown.md b/docs/generators/markdown.md
index 2cba7bc698ef..465504f69446 100644
--- a/docs/generators/markdown.md
+++ b/docs/generators/markdown.md
@@ -7,6 +7,16 @@ sidebar_label: markdown
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/nim.md b/docs/generators/nim.md
index 61ba1d00f1f5..0340561b620a 100644
--- a/docs/generators/nim.md
+++ b/docs/generators/nim.md
@@ -7,6 +7,16 @@ sidebar_label: nim
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/nodejs-express-server.md b/docs/generators/nodejs-express-server.md
index 76b0893f9a33..8cc7b8af1fcf 100644
--- a/docs/generators/nodejs-express-server.md
+++ b/docs/generators/nodejs-express-server.md
@@ -7,6 +7,16 @@ sidebar_label: nodejs-express-server
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |serverPort|TCP port to listen on.| |null|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/nodejs-server-deprecated.md b/docs/generators/nodejs-server-deprecated.md
index 84a3b1319439..b2b09ce303c0 100644
--- a/docs/generators/nodejs-server-deprecated.md
+++ b/docs/generators/nodejs-server-deprecated.md
@@ -9,6 +9,16 @@ sidebar_label: nodejs-server-deprecated
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |exportedName|When the generated code will be deployed to Google Cloud Functions, this option can be used to update the name of the exported function. By default, it refers to the basePath. This does not affect normal standalone nodejs server code.| |null|
 |googleCloudFunctions|When specified, it will generate the code which runs within Google Cloud Functions instead of standalone Node.JS server. See https://cloud.google.com/functions/docs/quickstart for the details of how to deploy the generated code.| |false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |serverPort|TCP port to listen on.| |null|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/ocaml.md b/docs/generators/ocaml.md
index d8cda30ed802..ab9a3bd7fd19 100644
--- a/docs/generators/ocaml.md
+++ b/docs/generators/ocaml.md
@@ -7,6 +7,16 @@ sidebar_label: ocaml
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/openapi-yaml.md b/docs/generators/openapi-yaml.md
index 7eda9d44be0d..3d7b5af16037 100644
--- a/docs/generators/openapi-yaml.md
+++ b/docs/generators/openapi-yaml.md
@@ -7,6 +7,16 @@ sidebar_label: openapi-yaml
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |outputFile|Output filename| |openapi/openapi.yaml|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/openapi.md b/docs/generators/openapi.md
index 5d46dccf4fd9..7625d70cb8b9 100644
--- a/docs/generators/openapi.md
+++ b/docs/generators/openapi.md
@@ -7,6 +7,16 @@ sidebar_label: openapi
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/php-laravel.md b/docs/generators/php-laravel.md
index 57b9191b6012..e2bbcaaab030 100644
--- a/docs/generators/php-laravel.md
+++ b/docs/generators/php-laravel.md
@@ -10,6 +10,16 @@ sidebar_label: php-laravel
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-lumen.md b/docs/generators/php-lumen.md
index 2414dda65c72..1e69867a13a4 100644
--- a/docs/generators/php-lumen.md
+++ b/docs/generators/php-lumen.md
@@ -10,6 +10,16 @@ sidebar_label: php-lumen
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-silex.md b/docs/generators/php-silex.md
index 81f5e6cb38c8..2557c8f15166 100644
--- a/docs/generators/php-silex.md
+++ b/docs/generators/php-silex.md
@@ -7,6 +7,16 @@ sidebar_label: php-silex
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/php-slim-deprecated.md b/docs/generators/php-slim-deprecated.md
index 98381616b95b..16b5a34e7614 100644
--- a/docs/generators/php-slim-deprecated.md
+++ b/docs/generators/php-slim-deprecated.md
@@ -10,6 +10,16 @@ sidebar_label: php-slim-deprecated
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-slim4.md b/docs/generators/php-slim4.md
index b0e79e02ae71..86f9a6efbc52 100644
--- a/docs/generators/php-slim4.md
+++ b/docs/generators/php-slim4.md
@@ -10,6 +10,16 @@ sidebar_label: php-slim4
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-symfony.md b/docs/generators/php-symfony.md
index 1d3e71d39265..e645d1c0a2dd 100644
--- a/docs/generators/php-symfony.md
+++ b/docs/generators/php-symfony.md
@@ -15,6 +15,16 @@ sidebar_label: php-symfony
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |phpLegacySupport|Should the generated code be compatible with PHP 5.x?| |true|
diff --git a/docs/generators/php-ze-ph.md b/docs/generators/php-ze-ph.md
index 93a1d3f6adf7..6afc5d2a291c 100644
--- a/docs/generators/php-ze-ph.md
+++ b/docs/generators/php-ze-ph.md
@@ -10,6 +10,16 @@ sidebar_label: php-ze-ph
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php.md b/docs/generators/php.md
index 413996804eb0..ba90aa92d7c9 100644
--- a/docs/generators/php.md
+++ b/docs/generators/php.md
@@ -11,6 +11,16 @@ sidebar_label: php
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/python-aiohttp.md b/docs/generators/python-aiohttp.md
index ee337d2e5bb2..0904e15e29c3 100644
--- a/docs/generators/python-aiohttp.md
+++ b/docs/generators/python-aiohttp.md
@@ -9,6 +9,16 @@ sidebar_label: python-aiohttp
 |controllerPackage|controller package| |controllers|
 |defaultController|default controller| |default_controller|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|python package name (convention: snake_case).| |openapi_server|
 |packageVersion|python package version.| |1.0.0|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/python-blueplanet.md b/docs/generators/python-blueplanet.md
index 0382237eef5c..ba1613ebe21c 100644
--- a/docs/generators/python-blueplanet.md
+++ b/docs/generators/python-blueplanet.md
@@ -9,6 +9,16 @@ sidebar_label: python-blueplanet
 |controllerPackage|controller package| |controllers|
 |defaultController|default controller| |default_controller|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|python package name (convention: snake_case).| |openapi_server|
 |packageVersion|python package version.| |1.0.0|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/python-flask.md b/docs/generators/python-flask.md
index c8ab554adeba..a09e1dd88945 100644
--- a/docs/generators/python-flask.md
+++ b/docs/generators/python-flask.md
@@ -9,6 +9,16 @@ sidebar_label: python-flask
 |controllerPackage|controller package| |controllers|
 |defaultController|default controller| |default_controller|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|python package name (convention: snake_case).| |openapi_server|
 |packageVersion|python package version.| |1.0.0|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/ruby.md b/docs/generators/ruby.md
index 2475a797ec6c..9bc917daa983 100644
--- a/docs/generators/ruby.md
+++ b/docs/generators/ruby.md
@@ -17,6 +17,16 @@ sidebar_label: ruby
 |gemSummary|gem summary. | |A ruby wrapper for the REST APIs|
 |gemVersion|gem version.| |1.0.0|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|HTTP library template (sub-template) to use|<dl><dt>**faraday**</dt><dd>Faraday (https://github.com/lostisland/faraday) (Beta support)</dd><dt>**typhoeus**</dt><dd>Typhoeus &gt;= 1.0.1 (https://github.com/typhoeus/typhoeus)</dd></dl>|typhoeus|
 |moduleName|top module name (convention: CamelCase, usually corresponding to gem name).| |OpenAPIClient|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-akka-http-server.md b/docs/generators/scala-akka-http-server.md
index ecd656979e35..5b293ffbc327 100644
--- a/docs/generators/scala-akka-http-server.md
+++ b/docs/generators/scala-akka-http-server.md
@@ -14,6 +14,16 @@ sidebar_label: scala-akka-http-server
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |groupId|groupId in generated pom.xml| |org.openapitools|
 |invokerPackage|root package for generated code| |org.openapitools.server|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-akka.md b/docs/generators/scala-akka.md
index ad8c5d485cf1..d023156775e9 100644
--- a/docs/generators/scala-akka.md
+++ b/docs/generators/scala-akka.md
@@ -9,6 +9,16 @@ sidebar_label: scala-akka
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |mainPackage|Top-level package name, which defines 'apiPackage', 'modelPackage', 'invokerPackage'| |org.openapitools.client|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/scala-gatling.md b/docs/generators/scala-gatling.md
index 0e1e748245e1..1b711480df22 100644
--- a/docs/generators/scala-gatling.md
+++ b/docs/generators/scala-gatling.md
@@ -9,6 +9,16 @@ sidebar_label: scala-gatling
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-httpclient-deprecated.md b/docs/generators/scala-httpclient-deprecated.md
index febeca9a6900..a6ee24cc4479 100644
--- a/docs/generators/scala-httpclient-deprecated.md
+++ b/docs/generators/scala-httpclient-deprecated.md
@@ -9,6 +9,16 @@ sidebar_label: scala-httpclient-deprecated
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-lagom-server.md b/docs/generators/scala-lagom-server.md
index 99b43af7d58c..da97ad1ee7df 100644
--- a/docs/generators/scala-lagom-server.md
+++ b/docs/generators/scala-lagom-server.md
@@ -9,6 +9,16 @@ sidebar_label: scala-lagom-server
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-play-server.md b/docs/generators/scala-play-server.md
index 57bdf5d70ed8..ef8b2db4e746 100644
--- a/docs/generators/scala-play-server.md
+++ b/docs/generators/scala-play-server.md
@@ -10,6 +10,16 @@ sidebar_label: scala-play-server
 |basePackage|Base package in which supporting classes are generated.| |org.openapitools|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |generateCustomExceptions|If set, generates custom exception types.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-sttp.md b/docs/generators/scala-sttp.md
index 5c277bf9dcc2..2d1584633b9c 100644
--- a/docs/generators/scala-sttp.md
+++ b/docs/generators/scala-sttp.md
@@ -9,6 +9,16 @@ sidebar_label: scala-sttp
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |mainPackage|Top-level package name, which defines 'apiPackage', 'modelPackage', 'invokerPackage'| |org.openapitools.client|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/scalatra.md b/docs/generators/scalatra.md
index af71e32aa463..bb05a8f35e89 100644
--- a/docs/generators/scalatra.md
+++ b/docs/generators/scalatra.md
@@ -9,6 +9,16 @@ sidebar_label: scalatra
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scalaz.md b/docs/generators/scalaz.md
index aa2f6121ca13..48ecb1bdfa70 100644
--- a/docs/generators/scalaz.md
+++ b/docs/generators/scalaz.md
@@ -9,6 +9,16 @@ sidebar_label: scalaz
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/spring.md b/docs/generators/spring.md
index 98b896d8f262..c2a43de8ceaf 100644
--- a/docs/generators/spring.md
+++ b/docs/generators/spring.md
@@ -35,6 +35,16 @@ sidebar_label: spring
 |interfaceOnly|Whether to generate only API interface stubs without the server files.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64. Use java8 default interface when a responseWrapper is used</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**spring-boot**</dt><dd>Spring-boot Server application using the SpringFox integration.</dd><dt>**spring-mvc**</dt><dd>Spring-MVC Server application using the SpringFox integration.</dd><dt>**spring-cloud**</dt><dd>Spring-Cloud-Feign client with Spring-Boot auto-configured settings.</dd></dl>|spring-boot|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/swift2-deprecated.md b/docs/generators/swift2-deprecated.md
index fe739bc109a2..34894b89301e 100644
--- a/docs/generators/swift2-deprecated.md
+++ b/docs/generators/swift2-deprecated.md
@@ -8,6 +8,16 @@ sidebar_label: swift2-deprecated
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |podAuthors|Authors used for Podspec| |null|
 |podDescription|Description used for Podspec| |null|
 |podDocsetURL|Docset URL used for Podspec| |null|
diff --git a/docs/generators/swift3-deprecated.md b/docs/generators/swift3-deprecated.md
index 7f1997eaef95..ed484208b2ce 100644
--- a/docs/generators/swift3-deprecated.md
+++ b/docs/generators/swift3-deprecated.md
@@ -8,6 +8,16 @@ sidebar_label: swift3-deprecated
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |lenientTypeCast|Accept and cast values for simple types (string-&gt;bool, string-&gt;int, int-&gt;string)| |false|
 |objcCompatible|Add additional properties and methods for Objective-C compatibility (default: false)| |null|
 |podAuthors|Authors used for Podspec| |null|
diff --git a/docs/generators/swift4.md b/docs/generators/swift4.md
index f4c589c02eab..4030c9a11f31 100644
--- a/docs/generators/swift4.md
+++ b/docs/generators/swift4.md
@@ -8,6 +8,16 @@ sidebar_label: swift4
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |lenientTypeCast|Accept and cast values for simple types (string-&gt;bool, string-&gt;int, int-&gt;string)| |false|
 |nonPublicApi|Generates code with reduced access modifiers; allows embedding elsewhere without exposing non-public API calls to consumers.(default: false)| |null|
 |objcCompatible|Add additional properties and methods for Objective-C compatibility (default: false)| |null|
diff --git a/docs/generators/swift5.md b/docs/generators/swift5.md
index 52a75bd93b1a..c7beb3e39abf 100644
--- a/docs/generators/swift5.md
+++ b/docs/generators/swift5.md
@@ -9,6 +9,16 @@ sidebar_label: swift5
 |apiNamePrefix|Prefix that will be appended to all API names ('tags'). Default: empty string. e.g. Pet =&gt; Pet.| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |lenientTypeCast|Accept and cast values for simple types (string-&gt;bool, string-&gt;int, int-&gt;string)| |false|
 |library|Library template (sub-template) to use|<dl><dt>**urlsession**</dt><dd>[DEFAULT] HTTP client: URLSession</dd><dt>**alamofire**</dt><dd>HTTP client: Alamofire</dd></dl>|urlsession|
 |nonPublicApi|Generates code with reduced access modifiers; allows embedding elsewhere without exposing non-public API calls to consumers.(default: false)| |null|
diff --git a/docs/generators/typescript-angular.md b/docs/generators/typescript-angular.md
index f382194df4ab..4d9191a91f0c 100644
--- a/docs/generators/typescript-angular.md
+++ b/docs/generators/typescript-angular.md
@@ -11,6 +11,16 @@ sidebar_label: typescript-angular
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
 |fileNaming|Naming convention for the output files: 'camelCase', 'kebab-case'.| |camelCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelFileSuffix|The suffix of the file of the generated model (model&lt;suffix&gt;.ts).| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |modelSuffix|The suffix of the generated model.| |null|
diff --git a/docs/generators/typescript-angularjs.md b/docs/generators/typescript-angularjs.md
index fbfd828ba323..0c5f755640ba 100644
--- a/docs/generators/typescript-angularjs.md
+++ b/docs/generators/typescript-angularjs.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-angularjs
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |nullSafeAdditionalProps|Set to make additional properties types declare that their indexer may return undefined| |false|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/typescript-aurelia.md b/docs/generators/typescript-aurelia.md
index 955079117b0e..f5f0e764b665 100644
--- a/docs/generators/typescript-aurelia.md
+++ b/docs/generators/typescript-aurelia.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-aurelia
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmVersion|The version of your npm package. If not provided, using the version from the OpenAPI specification file.| |1.0.0|
diff --git a/docs/generators/typescript-axios.md b/docs/generators/typescript-axios.md
index 5e65684a0e6e..575d2e17bbca 100644
--- a/docs/generators/typescript-axios.md
+++ b/docs/generators/typescript-axios.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-axios
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url of your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-fetch.md b/docs/generators/typescript-fetch.md
index 40e7ff4eb2cc..2662e2adefa5 100644
--- a/docs/generators/typescript-fetch.md
+++ b/docs/generators/typescript-fetch.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-fetch
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-inversify.md b/docs/generators/typescript-inversify.md
index 5d68c9f08399..6829b64eee83 100644
--- a/docs/generators/typescript-inversify.md
+++ b/docs/generators/typescript-inversify.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-inversify
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-jquery.md b/docs/generators/typescript-jquery.md
index 91d61cf31e10..262578ce207a 100644
--- a/docs/generators/typescript-jquery.md
+++ b/docs/generators/typescript-jquery.md
@@ -10,6 +10,16 @@ sidebar_label: typescript-jquery
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
 |jqueryAlreadyImported|When using this in legacy app using mix of typescript and javascript, this will only declare jquery and not import it| |false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-node.md b/docs/generators/typescript-node.md
index d4bdee29bcc8..06a4853986a9 100644
--- a/docs/generators/typescript-node.md
+++ b/docs/generators/typescript-node.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-node
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-redux-query.md b/docs/generators/typescript-redux-query.md
index e5674a4c302c..14fbe4c85434 100644
--- a/docs/generators/typescript-redux-query.md
+++ b/docs/generators/typescript-redux-query.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-redux-query
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-rxjs.md b/docs/generators/typescript-rxjs.md
index 9a210f4934b9..e9638e2fbdd3 100644
--- a/docs/generators/typescript-rxjs.md
+++ b/docs/generators/typescript-rxjs.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-rxjs
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java b/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java
index e40f3c624acc..084026f5552e 100644
--- a/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java
+++ b/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java
@@ -240,6 +240,9 @@ public class Generate extends OpenApiGeneratorCommand {
     @Option(name = {"--generate-alias-as-model"}, title = "generate alias (array, map) as model", description = CodegenConstants.GENERATE_ALIAS_AS_MODEL_DESC)
     private Boolean generateAliasAsModel;
 
+    @Option(name = {"--legacy-discriminator-behavior"}, title = "Support legacy logic for evaluating discriminators", description = CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR_DESC)
+    private Boolean legacyDiscriminatorBehavior;
+
     @Option(name = {"--minimal-update"},
         title = "Minimal update",
         description = "Only write output files that have changed.")
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java
index 14e1fe5fce33..5b2cc91645b5 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java
@@ -351,4 +351,17 @@ public static enum ENUM_PROPERTY_NAMING_TYPE {camelCase, PascalCase, snake_case,
 
     public static final String REMOVE_ENUM_VALUE_PREFIX = "removeEnumValuePrefix";
     public static final String REMOVE_ENUM_VALUE_PREFIX_DESC = "Remove the common prefix of enum values";
+
+    public static final String LEGACY_DISCRIMINATOR_BEHAVIOR = "legacyDiscriminatorBehavior";
+    public static final String LEGACY_DISCRIMINATOR_BEHAVIOR_DESC = "This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.\n" +
+            "\n" +
+            "When this flag is set to false:\n" +
+            "\n" +
+            "- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.\n" +
+            "- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.\n" +
+            "When this flag is set to true:\n" +
+            "\n" +
+            "- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.\n" +
+            "Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.";
+
 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java
index 73d85052e70d..4e30df0c9ea4 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java
@@ -7,12 +7,39 @@
 import java.util.Objects;
 import java.util.Set;
 
+/**
+ * This class encapsulates the OpenAPI discriminator construct, as specified at
+ * https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#discriminatorObject.
+ *
+ * When request bodies or response payloads may be one of a number of different schemas,
+ * a discriminator object can be used to aid in serialization, deserialization, and validation.
+ * The discriminator is a specific object in a schema which is used to inform the consumer of
+ * the specification of an alternative schema based on the value associated with it.
+ */
 public class CodegenDiscriminator {
+    // The name of the property in the payload that will hold the discriminator value.
+    // This is the propertyName as specified in the OpenAPI discriminator object.
     private String propertyName;
     private String propertyBaseName;
     private String propertyGetter;
     private String propertyType;
     private Map<String, String> mapping;
+
+    // mappedModels is populated differently if discriminatorExplicitMappingVerbose is
+    // True or False. When:
+    //
+    // discriminatorExplicitMappingVerbose == False, this contains:
+    // - the name to schema map info in the discriminator mapping entry in your openapi spec OR
+    // - child schemas that allOf inherit self schema
+    //
+    // discriminatorExplicitMappingVerbose == True, this contains:
+    // - the name to schema map info in the discriminMappedModelator mapping entry in your openapi spec AND
+    // - x-discriminator-value mappings in child oneOf + anyOf schemas + descendant schemas that allOf inherit self schema AND
+    // - descendant schemas that allOf inherit self schema AND
+    // - child oneOf + anyOf schemas
+    //
+    // see the method createDiscriminator in DefaultCodegen.java
+
     private Set<MappedModel> mappedModels = new LinkedHashSet<>();
 
     public String getPropertyName() {
@@ -63,8 +90,21 @@ public void setMappedModels(Set<MappedModel> mappedModels) {
         this.mappedModels = mappedModels;
     }
 
-    public static class MappedModel {
+    /**
+     * An object to hold discriminator mappings between payload values and schema names or
+     * references.
+     *
+     * In the OpenAPI document, the discriminator "mapping" attribute is optional.
+     * In scenarios where the value of the discriminator field does not match the schema name
+     * or implicit mapping is not possible, an optional mapping definition MAY be used.
+     * In OpenAPITools codegen, the MappedModel is the union of all the discriminator mappings,
+     * both explicitly defined in the OpenAPI document and inherited from oneOf/allOf/anyOf.
+     */
+    public static class MappedModel implements Comparable<MappedModel>{
+        // The value of the discriminator property in the payload.
         private String mappingName;
+        // The OAS schema name. It is obtained from the OAS document, and the string value
+        // is converted to a sanitized, internal representation within codegen.
         private String modelName;
 
         public MappedModel(String mappingName, String modelName) {
@@ -72,6 +112,18 @@ public MappedModel(String mappingName, String modelName) {
             this.modelName = modelName;
         }
 
+        @Override
+        public int compareTo(MappedModel other) {
+            if (getMappingName() == null && other.getMappingName() == null) {
+                return 0;
+            } else if (getMappingName() == null) {
+                return 1;
+            } else if (other.getMappingName() == null) {
+                return -1;
+            }
+            return getMappingName().compareTo(other.getMappingName());
+        }
+
         public String getMappingName() {
             return mappingName;
         }
@@ -130,4 +182,4 @@ public String toString() {
         sb.append('}');
         return sb.toString();
     }
-}
+}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java
index 16a296f84e1f..e9d25fd5ca74 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java
@@ -696,6 +696,17 @@ public String toString() {
         return sb.toString();
     }
 
+    public void addDiscriminatorMappedModelsImports(){
+        if (discriminator == null || discriminator.getMappedModels() == null) {
+            return;
+        }
+        for (CodegenDiscriminator.MappedModel mm : discriminator.getMappedModels()) {
+            if (!"".equals(mm.getModelName())) {
+                imports.add(mm.getModelName());
+            }
+        }
+    }
+
     public boolean isEmptyVars() {
         return emptyVars;
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
index b6255e1fe02d..bc1101c015e9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
@@ -150,6 +150,7 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public boolean isNullable;
     public boolean isSelfReference;
     public boolean isCircularReference;
+    public boolean isDiscriminator;
     public List<String> _enum;
     public Map<String, Object> allowableValues;
     public CodegenProperty items;
@@ -651,6 +652,7 @@ public String toString() {
         sb.append(", isNullable=").append(isNullable);
         sb.append(", isSelfReference=").append(isSelfReference);
         sb.append(", isCircularReference=").append(isCircularReference);
+        sb.append(", isDiscriminator=").append(isDiscriminator);
         sb.append(", _enum=").append(_enum);
         sb.append(", allowableValues=").append(allowableValues);
         sb.append(", items=").append(items);
@@ -717,6 +719,7 @@ public boolean equals(Object o) {
                 isNullable == that.isNullable &&
                 isSelfReference == that.isSelfReference &&
                 isCircularReference == that.isCircularReference &&
+                isDiscriminator == that.isDiscriminator &&
                 hasValidation == that.hasValidation &&
                 isInherited == that.isInherited &&
                 isXmlAttribute == that.isXmlAttribute &&
@@ -775,7 +778,7 @@ public int hashCode() {
                 isInteger, isLong, isNumber, isFloat, isDouble, isByteArray, isBinary, isFile,
                 isBoolean, isDate, isDateTime, isUuid, isUri, isEmail, isFreeFormObject,
                 isListContainer, isMapContainer, isEnum, isReadOnly, isWriteOnly, isNullable,
-                isSelfReference, isCircularReference, _enum, allowableValues, items, mostInnerItems,
+                isSelfReference, isCircularReference, isDiscriminator, _enum, allowableValues, items, mostInnerItems,
                 vendorExtensions, hasValidation, isInherited, discriminatorValue, nameInCamelCase,
                 nameInSnakeCase, enumName, maxItems, minItems, isXmlAttribute, xmlPrefix, xmlName,
                 xmlNamespace, isXmlWrapped);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index 6f5990074ce4..91edad3cd514 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -215,6 +215,9 @@ apiTemplateFiles are for API outputs only (controllers/handlers).
     // flag to indicate whether enum value prefixes are removed
     protected boolean removeEnumValuePrefix = true;
 
+    // Support legacy logic for evaluating discriminators
+    protected boolean legacyDiscriminatorBehavior = true;
+
     // make openapi available to all methods
     protected OpenAPI openAPI;
 
@@ -306,6 +309,11 @@ public void processOpts() {
             this.setRemoveEnumValuePrefix(Boolean.valueOf(additionalProperties
                     .get(CodegenConstants.REMOVE_ENUM_VALUE_PREFIX).toString()));
         }
+
+        if (additionalProperties.containsKey(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR)) {
+            this.setLegacyDiscriminatorBehavior(Boolean.valueOf(additionalProperties
+                    .get(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR).toString()));
+        }
     }
 
     /***
@@ -468,7 +476,8 @@ public Map<String, Object> updateAllModels(Map<String, Object> objs) {
                 }
                 parent.getChildren().add(cm);
                 parent.hasChildren = true;
-                if (parent.getDiscriminator() == null) {
+                Schema parentSchema = this.openAPI.getComponents().getSchemas().get(parent.name);
+                if (parentSchema.getDiscriminator() == null) {
                     parent = allModels.get(parent.getParent());
                 } else {
                     parent = null;
@@ -765,7 +774,7 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
                     if (e.getKey().contains("/")) {
                         // if this is property schema, we also need to generate the oneOf interface model
                         addOneOfNameExtension((ComposedSchema) s, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) s, nOneOf);
+                        addOneOfInterfaceModel((ComposedSchema) s, nOneOf, openAPI);
                     } else {
                         // else this is a component schema, so we will just use that as the oneOf interface model
                         addOneOfNameExtension((ComposedSchema) s, n);
@@ -774,13 +783,13 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
                     Schema items = ((ArraySchema) s).getItems();
                     if (ModelUtils.isComposedSchema(items)) {
                         addOneOfNameExtension((ComposedSchema) items, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) items, nOneOf);
+                        addOneOfInterfaceModel((ComposedSchema) items, nOneOf, openAPI);
                     }
                 } else if (ModelUtils.isMapSchema(s)) {
                     Schema addProps = ModelUtils.getAdditionalProperties(s);
                     if (addProps != null && ModelUtils.isComposedSchema(addProps)) {
                         addOneOfNameExtension((ComposedSchema) addProps, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) addProps, nOneOf);
+                        addOneOfInterfaceModel((ComposedSchema) addProps, nOneOf, openAPI);
                     }
                 }
             }
@@ -1109,6 +1118,14 @@ public void setEnsureUniqueParams(Boolean ensureUniqueParams) {
         this.ensureUniqueParams = ensureUniqueParams;
     }
 
+    public Boolean getLegacyDiscriminatorBehavior() {
+        return legacyDiscriminatorBehavior;
+    }
+
+    public void setLegacyDiscriminatorBehavior(boolean val){
+        this.legacyDiscriminatorBehavior = val;
+    }
+
     public Boolean getAllowUnicodeIdentifiers() {
         return allowUnicodeIdentifiers;
     }
@@ -1423,6 +1440,9 @@ public DefaultCodegen() {
         // option to change the order of form/body parameter
         cliOptions.add(CliOption.newBoolean(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS,
                 CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS_DESC).defaultValue(Boolean.FALSE.toString()));
+        cliOptions.add(CliOption.newBoolean(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR,
+                CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR_DESC).defaultValue(Boolean.TRUE.toString()));
+
 
         // initialize special character mapping
         initalizeSpecialCharacterMapping();
@@ -2115,7 +2135,10 @@ public CodegenModel fromModel(String name, Schema schema) {
         }
         m.isAlias = (typeAliases.containsKey(name)
                 || isAliasOfSimpleTypes(schema)); // check if the unaliased schema is an alias of simple OAS types
-        m.discriminator = createDiscriminator(name, schema);
+        m.discriminator = createDiscriminator(name, schema, this.openAPI);
+        if (!this.getLegacyDiscriminatorBehavior()) {
+            m.addDiscriminatorMappedModelsImports();
+        }
 
         if (schema.getDeprecated() != null) {
             m.isDeprecated = schema.getDeprecated();
@@ -2161,7 +2184,10 @@ public CodegenModel fromModel(String name, Schema schema) {
                     for (Schema innerSchema : composed.getAllOf()) { // TODO need to work with anyOf, oneOf as well
                         if (m.discriminator == null && innerSchema.getDiscriminator() != null) {
                             LOGGER.debug("discriminator is set to null (not correctly set earlier): {}", name);
-                            m.discriminator = createDiscriminator(name, innerSchema);
+                            m.discriminator = createDiscriminator(name, innerSchema, this.openAPI);
+                            if (!this.getLegacyDiscriminatorBehavior()) {
+                                m.addDiscriminatorMappedModelsImports();
+                            }
                             modelDiscriminators++;
                         }
 
@@ -2285,6 +2311,7 @@ public CodegenModel fromModel(String name, Schema schema) {
                 required.addAll(composed.getRequired());
                 allRequired.addAll(composed.getRequired());
             }
+
             addVars(m, unaliasPropertySchema(properties), required, unaliasPropertySchema(allProperties), allRequired);
 
             // end of code block for composed schema
@@ -2353,6 +2380,22 @@ public CodegenModel fromModel(String name, Schema schema) {
             }
         }
 
+        // set isDiscriminator on the discriminator property
+        if (m.discriminator != null) {
+            String discPropName = m.discriminator.getPropertyBaseName();
+            List<List<CodegenProperty>> listOLists = new ArrayList<List<CodegenProperty>>();
+            listOLists.add(m.requiredVars);
+            listOLists.add(m.vars);
+            listOLists.add(m.allVars);
+            for (List<CodegenProperty> theseVars: listOLists) {
+                for (CodegenProperty requiredVar: theseVars) {
+                    if (discPropName.equals(requiredVar.baseName)) {
+                        requiredVar.isDiscriminator = true;
+                    }
+                }
+            }
+        }
+
         if (sortModelPropertiesByRequiredFlag) {
             Comparator<CodegenProperty> comparator = new Comparator<CodegenProperty>() {
                 @Override
@@ -2369,36 +2412,316 @@ public int compare(CodegenProperty one, CodegenProperty another) {
         return m;
     }
 
-    protected CodegenDiscriminator createDiscriminator(String schemaName, Schema schema) {
-        if (schema.getDiscriminator() == null) {
+    /**
+     * Recursively look in Schema sc for the discriminator discPropName
+     * and return a CodegenProperty with the dataType and required params set
+     * the returned CodegenProperty may not be required and it may not be of type string
+     * @param composedSchemaName The name of the sc Schema
+     * @param sc The Schema that may contain the discriminator
+     * @param discPropName The String that is the discriminator propertyName in the schema
+     */
+    private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc, String discPropName, OpenAPI openAPI) {
+        Schema refSchema = ModelUtils.getReferencedSchema(openAPI, sc);
+        if (refSchema.getProperties() != null && refSchema.getProperties().get(discPropName) != null) {
+            Schema discSchema = (Schema) refSchema.getProperties().get(discPropName);
+            CodegenProperty cp = new CodegenProperty();
+            if (ModelUtils.isStringSchema(discSchema)) {
+                cp.isString = true;
+            }
+            cp.setRequired(false);
+            if (refSchema.getRequired() != null && refSchema.getRequired().contains(discPropName)) {
+                cp.setRequired(true);
+            }
+            return cp;
+        }
+        if (ModelUtils.isComposedSchema(refSchema)) {
+            ComposedSchema composedSchema = (ComposedSchema) refSchema;
+            if (composedSchema.getAllOf() != null) {
+                // If our discriminator is in one of the allOf schemas break when we find it
+                for  (Schema allOf: composedSchema.getAllOf()) {
+                    CodegenProperty cp = discriminatorFound(composedSchemaName, allOf, discPropName, openAPI);
+                    if (cp != null) {
+                        return cp;
+                    }
+                }
+            }
+            if (composedSchema.getOneOf() != null && composedSchema.getOneOf().size() != 0) {
+                // All oneOf definitions must contain the discriminator
+                CodegenProperty cp = new CodegenProperty();
+                for  (Schema oneOf: composedSchema.getOneOf()) {
+                    String modelName = ModelUtils.getSimpleRef(oneOf.get$ref());
+                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, oneOf, discPropName, openAPI);
+                    if (thisCp == null) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the referenced OneOf schema '" + modelName + "' is missing "+discPropName);
+                    }
+                    if (cp.dataType == null) {
+                        cp = thisCp;
+                        continue;
+                    }
+                    if (cp != thisCp) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the OneOf schema '" + modelName + "' has a different "+discPropName+" definition than the prior OneOf schema's. Make sure the "+discPropName+" type and required values are the same");
+                    }
+                }
+                return cp;
+            }
+            if (composedSchema.getAnyOf() != null && composedSchema.getAnyOf().size() != 0) {
+                // All anyOf definitions must contain the discriminator because a min of one must be selected
+                CodegenProperty cp = new CodegenProperty();
+                for  (Schema anyOf: composedSchema.getAnyOf()) {
+                    String modelName = ModelUtils.getSimpleRef(anyOf.get$ref());
+                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, anyOf, discPropName, openAPI);
+                    if (thisCp == null) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the referenced AnyOf schema '" + modelName + "' is missing "+discPropName);
+                    }
+                    if (cp.dataType == null) {
+                        cp = thisCp;
+                        continue;
+                    }
+                    if (cp != thisCp) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the AnyOf schema '" + modelName + "' has a different "+discPropName+" definition than the prior AnyOf schema's. Make sure the "+discPropName+" type and required values are the same");
+                    }
+                }
+                return cp;
+
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Recursively look in Schema sc for the discriminator and return it
+     * Schema sc location
+     * OpenAPI openAPI the spec where we are searching for the discriminator
+     * @param sc The Schema that may contain the discriminator
+     */
+    private Discriminator recursiveGetDiscriminator(Schema sc, OpenAPI openAPI) {
+        Schema refSchema = ModelUtils.getReferencedSchema(openAPI, sc);
+        Discriminator foundDisc = refSchema.getDiscriminator();
+        if (foundDisc != null) {
+            return foundDisc;
+        }
+        if (!!this.getLegacyDiscriminatorBehavior()) {
+            return null;
+        }
+        Discriminator disc = new Discriminator();
+        if (ModelUtils.isComposedSchema(refSchema)) {
+            ComposedSchema composedSchema = (ComposedSchema) refSchema;
+            if (composedSchema.getAllOf() != null) {
+                // If our discriminator is in one of the allOf schemas break when we find it
+                for  (Schema allOf: composedSchema.getAllOf()) {
+                    foundDisc = recursiveGetDiscriminator(allOf, openAPI);
+                    if (foundDisc != null) {
+                        disc.setPropertyName(foundDisc.getPropertyName());
+                        disc.setMapping(foundDisc.getMapping());
+                        return disc;
+                    }
+                }
+            }
+            if (composedSchema.getOneOf() != null && composedSchema.getOneOf().size() != 0) {
+                // All oneOf definitions must contain the discriminator
+                Integer hasDiscriminatorCnt = 0;
+                Set<String> discriminatorsPropNames = new HashSet<>();
+                for  (Schema oneOf: composedSchema.getOneOf()) {
+                    foundDisc = recursiveGetDiscriminator(oneOf, openAPI);
+                    if (foundDisc != null) {
+                        discriminatorsPropNames.add(foundDisc.getPropertyName());
+                        hasDiscriminatorCnt++;
+                    }
+                }
+                if (hasDiscriminatorCnt == composedSchema.getOneOf().size() && discriminatorsPropNames.size() == 1) {
+                    disc.setPropertyName(foundDisc.getPropertyName());
+                    disc.setMapping(foundDisc.getMapping());
+                    return disc;
+                }
+            }
+            if (composedSchema.getAnyOf() != null && composedSchema.getAnyOf().size() != 0) {
+                // All anyOf definitions must contain the discriminator because a min of one must be selected
+                Integer hasDiscriminatorCnt = 0;
+                Set<String> discriminatorsPropNames = new HashSet<>();
+                for  (Schema anyOf: composedSchema.getAnyOf()) {
+                    foundDisc = recursiveGetDiscriminator(anyOf, openAPI);
+                    if (foundDisc != null) {
+                        discriminatorsPropNames.add(foundDisc.getPropertyName());
+                        hasDiscriminatorCnt++;
+                    }
+                }
+                if (hasDiscriminatorCnt == composedSchema.getAnyOf().size() && discriminatorsPropNames.size() == 1) {
+                    disc.setPropertyName(foundDisc.getPropertyName());
+                    disc.setMapping(foundDisc.getMapping());
+                    return disc;
+                }
+            }
+        }
+        return null;
+    }
+
+    /**
+     * This function is only used for composed schemas which have a discriminator
+     * Process oneOf and anyOf models in a composed schema and adds them into
+     * a list if the oneOf and anyOf models contain
+     * the required discriminator. If they don't contain the required
+     * discriminator or the discriminator is the wrong type then an error is
+     * thrown
+     * @param composedSchemaName The String model name of the composed schema where we are setting the discriminator map
+     * @param discPropName The String that is the discriminator propertyName in the schema
+     * @param c The ComposedSchema that contains the discriminator and oneOf/anyOf schemas
+     * @param openAPI The OpenAPI spec that we are using
+     * @return the list of oneOf and anyOf MappedModel that need to be added to the discriminator map
+     */
+    protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName, String discPropName, ComposedSchema c, OpenAPI openAPI) {
+        ArrayList<List<Schema>> listOLists = new ArrayList<List<Schema>>();
+        listOLists.add(c.getOneOf());
+        listOLists.add(c.getAnyOf());
+        List<MappedModel> descendentSchemas = new ArrayList();
+        for (List<Schema> schemaList: listOLists) {
+            if (schemaList == null) {
+                continue;
+            }
+            for  (Schema sc: schemaList) {
+                String ref = sc.get$ref();
+                if (ref == null) {
+                    // for schemas with no ref, it is not possible to build the discriminator map
+                    // because ref is how we get the model name
+                    // we only hit this use case for a schema with inline composed schemas, and one of those
+                    // schemas also has inline composed schemas
+                    // Note: if it is only inline one level, then the inline model resolver will move it into its own
+                    // schema and make it a $ref schema in the oneOf/anyOf location
+                    throw new RuntimeException("Invalid inline schema defined in oneOf/anyOf in '" + composedSchemaName + "'. Per the OpenApi spec, for this case when a composed schema defines a discriminator, the oneOf/anyOf schemas must use $ref. Change this inline definition to a $ref definition");
+                }
+                CodegenProperty df = discriminatorFound(composedSchemaName, sc, discPropName, openAPI);
+                String modelName = ModelUtils.getSimpleRef(ref);
+                if (df == null || !df.isString || df.required != true) {
+                    String msgSuffix = "";
+                    if (df == null) {
+                        msgSuffix += discPropName+" is missing from the schema, define it as required and type string";
+                    } else {
+                        if (!df.isString) {
+                            msgSuffix += "invalid type for "+discPropName+", set it to string";
+                        }
+                        if (df.required != true) {
+                            String spacer = "";
+                            if (msgSuffix.length() != 0) {
+                                spacer = ". ";
+                            }
+                            msgSuffix += spacer+"invalid optional definition of "+discPropName+", include it in required";
+                        }
+                    }
+                    throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the referenced schema '" + modelName + "' is incorrect. "+msgSuffix);
+                }
+                MappedModel mm = new MappedModel(modelName, toModelName(modelName));
+                descendentSchemas.add(mm);
+                Schema cs = ModelUtils.getSchema(openAPI, modelName);
+                Map<String, Object> vendorExtensions = cs.getExtensions();
+                if (vendorExtensions != null && !vendorExtensions.isEmpty() && vendorExtensions.containsKey("x-discriminator-value")) {
+                    String xDiscriminatorValue = (String) vendorExtensions.get("x-discriminator-value");
+                    mm = new MappedModel(xDiscriminatorValue, toModelName(modelName));
+                    descendentSchemas.add(mm);
+                }
+
+            }
+        }
+        return descendentSchemas;
+    }
+
+    protected List<MappedModel> getAllOfDescendants(String thisSchemaName, OpenAPI openAPI) {
+        ArrayList<String> queue = new ArrayList();;
+        List<MappedModel> descendentSchemas = new ArrayList();
+        Map<String, Schema> schemas = ModelUtils.getSchemas(openAPI);
+        String currentSchemaName = thisSchemaName;
+        while (true) {
+            for (String childName : schemas.keySet()) {
+                if (childName == thisSchemaName) {
+                    continue;
+                }
+                Schema child = schemas.get(childName);
+                if (ModelUtils.isComposedSchema(child)) {
+                    ComposedSchema composedChild = (ComposedSchema) child;
+                    List<Schema> parents = composedChild.getAllOf();
+                    if (parents != null) {
+                        for  (Schema parent: parents) {
+                            String ref = parent.get$ref();
+                            if (ref == null) {
+                                // for schemas with no ref, it is not possible to build the discriminator map
+                                // because ref is how we get the model name
+                                // we only hit this use case for a schema with inline composed schemas, and one of those
+                                // schemas also has inline composed schemas
+                                throw new RuntimeException("Invalid inline schema defined in allOf in '" + childName + "'. Per the OpenApi spec, for this case when a composed schema defines a discriminator, the allOf schemas must use $ref. Change this inline definition to a $ref definition");
+                            }
+                            String parentName = ModelUtils.getSimpleRef(ref);
+                            if (parentName.equals(currentSchemaName)) {
+                                if (queue.contains(childName) || descendentSchemas.contains(childName)) {
+                                    throw new RuntimeException("Stack overflow hit when looking for "+thisSchemaName+" an infinite loop starting and ending at "+childName+" was seen");
+                                }
+                                queue.add(childName);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+            if (queue.size() == 0) {
+                break;
+            }
+            currentSchemaName = queue.remove(0);
+            MappedModel mm = new MappedModel(currentSchemaName, toModelName(currentSchemaName));
+            descendentSchemas.add(mm);
+            Schema cs = schemas.get(currentSchemaName);
+            Map<String, Object> vendorExtensions = cs.getExtensions();
+            if (vendorExtensions != null && !vendorExtensions.isEmpty() && vendorExtensions.containsKey("x-discriminator-value")) {
+                String xDiscriminatorValue = (String) vendorExtensions.get("x-discriminator-value");
+                mm = new MappedModel(xDiscriminatorValue, toModelName(currentSchemaName));
+                descendentSchemas.add(mm);
+            }
+        }
+        return descendentSchemas;
+    }
+
+    protected CodegenDiscriminator createDiscriminator(String schemaName, Schema schema, OpenAPI openAPI) {
+        Discriminator sourceDiscriminator = recursiveGetDiscriminator(schema, openAPI);
+        if (sourceDiscriminator == null) {
             return null;
         }
         CodegenDiscriminator discriminator = new CodegenDiscriminator();
-        discriminator.setPropertyName(toVarName(schema.getDiscriminator().getPropertyName()));
-        discriminator.setPropertyBaseName(schema.getDiscriminator().getPropertyName());
+        String discPropName = sourceDiscriminator.getPropertyName();
+        discriminator.setPropertyName(toVarName(discPropName));
+        discriminator.setPropertyBaseName(sourceDiscriminator.getPropertyName());
         discriminator.setPropertyGetter(toGetter(discriminator.getPropertyName()));
         // FIXME: for now, we assume that the discriminator property is String
         discriminator.setPropertyType(typeMapping.get("string"));
-        discriminator.setMapping(schema.getDiscriminator().getMapping());
-        if (schema.getDiscriminator().getMapping() != null && !schema.getDiscriminator().getMapping().isEmpty()) {
-            for (Entry<String, String> e : schema.getDiscriminator().getMapping().entrySet()) {
+        discriminator.setMapping(sourceDiscriminator.getMapping());
+        List<MappedModel> uniqueDescendants = new ArrayList();
+        if (sourceDiscriminator.getMapping() != null && !sourceDiscriminator.getMapping().isEmpty()) {
+            for (Entry<String, String> e : sourceDiscriminator.getMapping().entrySet()) {
                 String nameOrRef = e.getValue();
                 String name = nameOrRef.indexOf('/') >= 0 ? ModelUtils.getSimpleRef(nameOrRef) : nameOrRef;
                 String modelName = toModelName(name);
-                discriminator.getMappedModels().add(new MappedModel(e.getKey(), modelName));
+                uniqueDescendants.add(new MappedModel(e.getKey(), modelName));
             }
-        } else {
-            Map<String, Schema> allDefinitions = ModelUtils.getSchemas(this.openAPI);
-            allDefinitions.forEach((childName, child) -> {
-                if (child instanceof ComposedSchema && ((ComposedSchema) child).getAllOf() != null) {
+        }
 
-                    final List<String> parentSchemas = ModelUtils.getAllParentsName((ComposedSchema) child, allDefinitions, true);
-                    if (parentSchemas.contains(schemaName)) {
-                        discriminator.getMappedModels().add(new MappedModel(childName, toModelName(childName)));
-                    }
+        boolean legacyUseCase = (this.getLegacyDiscriminatorBehavior() && uniqueDescendants.isEmpty());
+        if (!this.getLegacyDiscriminatorBehavior() || legacyUseCase) {
+            // for schemas that allOf inherit from this schema, add those descendants to this discriminator map
+            List<MappedModel> otherDescendants = getAllOfDescendants(schemaName, openAPI);
+            for (MappedModel otherDescendant: otherDescendants) {
+                if (!uniqueDescendants.contains(otherDescendant)) {
+                    uniqueDescendants.add(otherDescendant);
                 }
-            });
+            }
         }
+        // if there are composed oneOf/anyOf schemas, add them to this discriminator
+        if (ModelUtils.isComposedSchema(schema) && !this.getLegacyDiscriminatorBehavior()) {
+            List<MappedModel> otherDescendants = getOneOfAnyOfDescendants(schemaName, discPropName, (ComposedSchema) schema, openAPI);
+            for (MappedModel otherDescendant: otherDescendants) {
+                if (!uniqueDescendants.contains(otherDescendant)) {
+                    uniqueDescendants.add(otherDescendant);
+                }
+            }
+        }
+        if (!this.getLegacyDiscriminatorBehavior()) {
+            Collections.sort(uniqueDescendants);
+        }
+        discriminator.getMappedModels().addAll(uniqueDescendants);
         return discriminator;
     }
 
@@ -2428,11 +2751,15 @@ protected void addProperties(Map<String, Schema> properties, List<String> requir
             }
 
             if (composedSchema.getOneOf() != null) {
-                throw new RuntimeException("Please report the issue: Cannot process oneOf (Composed Scheme) in addProperties: " + schema);
+                for (Schema component : composedSchema.getOneOf()) {
+                    addProperties(properties, required, component);
+                }
             }
 
             if (composedSchema.getAnyOf() != null) {
-                throw new RuntimeException("Please report the issue: Cannot process anyOf (Composed Schema) in addProperties: " + schema);
+                for (Schema component : composedSchema.getAnyOf()) {
+                    addProperties(properties, required, component);
+                }
             }
 
             return;
@@ -5830,15 +6157,19 @@ public void addOneOfNameExtension(ComposedSchema s, String name) {
      *
      * @param cs   ComposedSchema object to create as interface model
      * @param type name to use for the generated interface model
+     * @param openAPI OpenAPI spec that we are using
      */
-    public void addOneOfInterfaceModel(ComposedSchema cs, String type) {
+    public void addOneOfInterfaceModel(ComposedSchema cs, String type, OpenAPI openAPI) {
         if (cs.getOneOf() == null) {
             return;
         }
-        CodegenModel cm = new CodegenModel();
 
-        cm.discriminator = createDiscriminator("", (Schema) cs);
+        CodegenModel cm = new CodegenModel();
 
+        cm.discriminator = createDiscriminator("", (Schema) cs, openAPI);
+        if (!this.getLegacyDiscriminatorBehavior()) {
+            cm.addDiscriminatorMappedModelsImports();
+        }
         for (Schema o : Optional.ofNullable(cs.getOneOf()).orElse(Collections.emptyList())) {
             if (o.get$ref() == null) {
                 if (cm.discriminator != null && o.get$ref() == null) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
index e8dab26d05f9..1681434c4424 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
@@ -156,7 +156,7 @@ private Boolean getGeneratorPropertyDefaultSwitch(final String key, final Boolea
         return defaultValue;
     }
 
-    private void configureGeneratorProperties() {
+    void configureGeneratorProperties() {
         // allows generating only models by specifying a CSV of models to generate, or empty for all
         // NOTE: Boolean.TRUE is required below rather than `true` because of JVM boxing constraints and type inference.
         generateApis = GlobalSettings.getProperty(CodegenConstants.APIS) != null ? Boolean.TRUE : getGeneratorPropertyDefaultSwitch(CodegenConstants.APIS, null);
@@ -394,7 +394,7 @@ private void generateModel(List<File> files, Map<String, Object> models, String
     }
 
     @SuppressWarnings("unchecked")
-    private void generateModels(List<File> files, List<Object> allModels, List<String> unusedModels) {
+    void generateModels(List<File> files, List<Object> allModels, List<String> unusedModels) {
         if (!generateModels) {
             // TODO: Process these anyway and add to dryRun info
             LOGGER.info("Skipping generation of models.");
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
index 56c63ec0c630..89e189c8c388 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
@@ -77,6 +77,7 @@ public String getHelp() {
 
     @Override
     public void processOpts() {
+        this.setLegacyDiscriminatorBehavior(false);
         super.processOpts();
         supportingFiles.add(new SupportingFile("utils.mustache", "", "utils.go"));
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
index 8d2544c6af7f..6aa9c08250c9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
@@ -111,6 +111,8 @@ public PythonClientExperimentalCodegen() {
 
     @Override
     public void processOpts() {
+        this.setLegacyDiscriminatorBehavior(false);
+
         super.processOpts();
 
         supportingFiles.remove(new SupportingFile("api_client.mustache", packagePath(), "api_client.py"));
diff --git a/modules/openapi-generator/src/main/resources/Java/pojo.mustache b/modules/openapi-generator/src/main/resources/Java/pojo.mustache
index c438cd43eb72..653f44062d14 100644
--- a/modules/openapi-generator/src/main/resources/Java/pojo.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/pojo.mustache
@@ -69,7 +69,7 @@ public class {{classname}} {{#parent}}extends {{{parent}}} {{/parent}}{{#vendorE
   private {{{datatypeWithEnum}}} {{name}}{{#required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{/required}}{{^required}} = null{{/required}};
   {{/isContainer}}
   {{^isContainer}}
-  private {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
+  {{#isDiscriminator}}protected{{/isDiscriminator}}{{^isDiscriminator}}private{{/isDiscriminator}} {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
   {{/isContainer}}
   {{/vendorExtensions.x-is-jackson-optional-nullable}}
 
diff --git a/modules/openapi-generator/src/main/resources/python/api_client.mustache b/modules/openapi-generator/src/main/resources/python/api_client.mustache
index c69e7d5945ef..de25b7cf9754 100644
--- a/modules/openapi-generator/src/main/resources/python/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/python/api_client.mustache
@@ -643,9 +643,12 @@ class ApiClient(object):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -659,7 +662,7 @@ class ApiClient(object):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/modules/openapi-generator/src/main/resources/python/model.mustache b/modules/openapi-generator/src/main/resources/python/model.mustache
index 70f6e7489a7e..112246604dc5 100644
--- a/modules/openapi-generator/src/main/resources/python/model.mustache
+++ b/modules/openapi-generator/src/main/resources/python/model.mustache
@@ -52,8 +52,9 @@ class {{classname}}(object):
 {{#discriminator}}
 
     discriminator_value_class_map = {
-        {{#children}}'{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{vendorExtensions.x-discriminator-value}}}{{/vendorExtensions.x-discriminator-value}}': '{{{classname}}}'{{^-last}},
-        {{/-last}}{{/children}}
+{{#children}}
+        '{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{vendorExtensions.x-discriminator-value}}}{{/vendorExtensions.x-discriminator-value}}': '{{{classname}}}'{{^-last}},{{/-last}}
+{{/children}}
     }
 {{/discriminator}}
 
diff --git a/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache b/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache
index 60fff484ef40..8b49e58edbf2 100644
--- a/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache
+++ b/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache
@@ -115,15 +115,11 @@
 
     @staticmethod
     def discriminator():
-        return {{^discriminator}}None{{/discriminator}}{{#discriminator}}{
-            '{{{discriminatorName}}}': {
-{{#children}}
-                '{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{vendorExtensions.x-discriminator-value}}}{{/vendorExtensions.x-discriminator-value}}': {{{classname}}},
-{{/children}}
-{{^children}}
+        {{^discriminator}}return None{{/discriminator}}{{#discriminator}}val = {
 {{#mappedModels}}
-                '{{mappingName}}': {{{modelName}}},
+            '{{mappingName}}': {{{modelName}}},
 {{/mappedModels}}
-{{/children}}
-            },
-        }{{/discriminator}}
\ No newline at end of file
+        }
+        if not val:
+            return None
+        return {'{{{discriminatorName}}}': val}{{/discriminator}}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java
index 93ddc121dfa7..b6d5280a003e 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java
@@ -33,6 +33,7 @@
 import io.swagger.v3.oas.models.responses.ApiResponses;
 import io.swagger.v3.parser.core.models.ParseOptions;
 
+import org.openapitools.codegen.languages.JavaClientCodegen;
 import org.openapitools.codegen.templating.mustache.CamelCaseLambda;
 import org.openapitools.codegen.templating.mustache.IndentedLambda;
 import org.openapitools.codegen.templating.mustache.LowercaseLambda;
@@ -42,6 +43,7 @@
 import org.testng.Assert;
 import org.testng.annotations.Test;
 
+import java.io.File;
 import java.util.*;
 import java.util.stream.Collectors;
 
@@ -569,6 +571,7 @@ public void testDiscriminator() {
     public void testDiscriminatorWithCustomMapping() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf.yaml");
         DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
         codegen.setOpenAPI(openAPI);
 
         String path = "/person/display/{personId}";
@@ -635,6 +638,570 @@ public void testAllParents() {
         Assert.assertEquals(adultModel.allParents, Collections.singletonList("Person"));
     }
 
+    @Test
+    public void testComposedSchemaAllOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.setLegacyDiscriminatorBehavior(false);
+        Schema sc;
+        String modelName;
+
+        String propertyName = "petType";
+        String propertyBaseName = propertyName;
+        CodegenDiscriminator emptyMapDisc = new CodegenDiscriminator();
+        emptyMapDisc.setPropertyName(propertyName);
+        emptyMapDisc.setPropertyBaseName(propertyBaseName);
+
+        // all leaf Schemas have discriminators with PropertyName/BaseName + empty discriminator maps
+        List<String> leafModelNames = Arrays.asList("Cat", "Dog", "Lizard", "Snake");
+        for (String leafModelName: leafModelNames) {
+            Schema leafSc = openAPI.getComponents().getSchemas().get(leafModelName);
+            CodegenModel leafCm = codegen.fromModel(leafModelName, leafSc);
+            Assert.assertEquals(leafCm.discriminator, emptyMapDisc);
+        }
+
+        // the Pet discriminator map contains all animals + Reptile (children + grandchildren)
+        CodegenDiscriminator petDisc = new CodegenDiscriminator();
+        petDisc.setPropertyName(propertyName);
+        petDisc.setPropertyBaseName(propertyBaseName);
+        java.util.LinkedHashSet hs = new LinkedHashSet<>();
+        for (String leafModelName: leafModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(leafModelName, codegen.toModelName(leafModelName)));
+        }
+        hs.add(new CodegenDiscriminator.MappedModel("Reptile", codegen.toModelName("Reptile")));
+        petDisc.setMappedModels(hs);
+        modelName = "Pet";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel pet = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(pet.discriminator, petDisc);
+
+        // the Reptile discriminator contains both reptiles
+        List<String> reptileModelNames = Arrays.asList("Lizard", "Snake");
+        CodegenDiscriminator reptileDisc = new CodegenDiscriminator();
+        reptileDisc.setPropertyName(propertyName);
+        reptileDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        for (String reptileModelName: reptileModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(reptileModelName, codegen.toModelName(reptileModelName)));
+        }
+        reptileDisc.setMappedModels(hs);
+        modelName = "Reptile";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel reptile = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(reptile.discriminator, reptileDisc);
+
+        // the MyPets discriminator contains Cat and Lizard
+        List<String> myPetNames = Arrays.asList("Cat", "Lizard");
+        CodegenDiscriminator myPetDisc = new CodegenDiscriminator();
+        myPetDisc.setPropertyName(propertyName);
+        myPetDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        for (String myPetName: myPetNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(myPetName, codegen.toModelName(myPetName)));
+        }
+        myPetDisc.setMappedModels(hs);
+        modelName = "MyPets";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPets = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPets.discriminator, myPetDisc);
+
+        // the MyPetsNoDisc discriminator is created because all oneOf classes have the same discriminator
+        modelName = "MyPetsNoDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPetsNoDisc = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPetsNoDisc.discriminator, myPetDisc);
+
+        CodegenModel cm;
+
+        // the mapping in b is in A
+        modelName = "A";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        hs.add(new CodegenDiscriminator.MappedModel("B", codegen.toModelName("B")));
+        hs.add(new CodegenDiscriminator.MappedModel("C", codegen.toModelName("C")));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // the mapping in b is in B
+        modelName = "B";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        hs.add(new CodegenDiscriminator.MappedModel("C", codegen.toModelName("C")));
+
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // the mapping in b is in C
+        modelName = "C";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+    }
+
+    @Test
+    public void testComposedSchemaAllOfDiscriminatorMapLegacy() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        // codegen.discriminatorExplicitMappingVerbose remains false in the legacy use case
+        codegen.setOpenAPI(openAPI);
+        Schema sc;
+        String modelName;
+
+        String propertyName = "petType";
+        String propertyBaseName = propertyName;
+        CodegenDiscriminator emptyMapDisc = new CodegenDiscriminator();
+        emptyMapDisc.setPropertyName(propertyName);
+        emptyMapDisc.setPropertyBaseName(propertyBaseName);
+
+        // all leaf Schemas have discriminators with PropertyName/BaseName + empty discriminator maps
+        List<String> leafModelNames = Arrays.asList("Cat", "Dog", "Lizard", "Snake");
+        for (String leafModelName: leafModelNames) {
+            Schema leafSc = openAPI.getComponents().getSchemas().get(leafModelName);
+            CodegenModel leafCm = codegen.fromModel(leafModelName, leafSc);
+            Assert.assertEquals(leafCm.discriminator, null);
+        }
+
+        // the Pet discriminator map contains all animals + Reptile (children + grandchildren)
+        CodegenDiscriminator petDisc = new CodegenDiscriminator();
+        petDisc.setPropertyName(propertyName);
+        petDisc.setPropertyBaseName(propertyBaseName);
+        java.util.LinkedHashSet hs = new LinkedHashSet<>();
+        for (String leafModelName: leafModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(leafModelName, codegen.toModelName(leafModelName)));
+        }
+        hs.add(new CodegenDiscriminator.MappedModel("Reptile", codegen.toModelName("Reptile")));
+        petDisc.setMappedModels(hs);
+        modelName = "Pet";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel pet = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(pet.discriminator, petDisc);
+
+        // the Reptile discriminator contains both reptiles
+        List<String> reptileModelNames = Arrays.asList("Lizard", "Snake");
+        CodegenDiscriminator reptileDisc = new CodegenDiscriminator();
+        reptileDisc.setPropertyName(propertyName);
+        reptileDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        for (String reptileModelName: reptileModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(reptileModelName, codegen.toModelName(reptileModelName)));
+        }
+        reptileDisc.setMappedModels(hs);
+        modelName = "Reptile";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel reptile = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(reptile.discriminator, null);
+
+        // the MyPets discriminator contains Cat and Lizard
+        CodegenDiscriminator myPetDisc = new CodegenDiscriminator();
+        myPetDisc.setPropertyName(propertyName);
+        myPetDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        modelName = "MyPets";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPets = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPets.discriminator, myPetDisc);
+
+        // the MyPetsNoDisc discriminator is created because all oneOf classes have the same discriminator
+        modelName = "MyPetsNoDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPetsNoDisc = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPetsNoDisc.discriminator, null);
+
+        CodegenModel cm;
+
+        // the mapping in b is in A
+        modelName = "A";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // the mapping in b is in B
+        modelName = "B";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(cm.discriminator, null);
+
+        // the mapping in b is in C
+        modelName = "C";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(cm.discriminator, null);
+    }
+
+    @Test
+    public void testComposedSchemaOneOfDiscriminatorsInvalid() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        HashMap<String, String> hm = new HashMap<>();
+        hm.put("ComposedDiscMissingNoProperties", "'ComposedDiscMissingNoProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingNoProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscMissingFromProperties", "'ComposedDiscMissingFromProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingFromProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscOptionalTypeCorrect", "'ComposedDiscOptionalTypeCorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeIncorrect", "'ComposedDiscOptionalTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeInconsistent", "'ComposedDiscOptionalTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscTypeIncorrect", "'ComposedDiscTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscTypeInconsistent", "'ComposedDiscTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscRequiredInconsistent", "'ComposedDiscRequiredInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+
+        for(Map.Entry<String, String> entry : hm.entrySet()) {
+            String modelName = entry.getKey();
+            String errorMessageExpected = entry.getValue();
+
+            Schema sc = openAPI.getComponents().getSchemas().get(modelName);
+
+            try {
+                codegen.fromModel(modelName, sc);
+                Assert.assertTrue(false, "A RuntimeException should have been thrown when processing "+modelName+ " but it was not");
+            } catch (RuntimeException re) {
+                Assert.assertEquals(re.getMessage(), errorMessageExpected);
+            }
+        }
+    }
+
+    @Test
+    public void testComposedSchemaAnyOfDiscriminatorsInvalid() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/anyOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        HashMap<String, String> hm = new HashMap<>();
+        hm.put("ComposedDiscMissingNoProperties", "'ComposedDiscMissingNoProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingNoProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscMissingFromProperties", "'ComposedDiscMissingFromProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingFromProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscOptionalTypeCorrect", "'ComposedDiscOptionalTypeCorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeIncorrect", "'ComposedDiscOptionalTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeInconsistent", "'ComposedDiscOptionalTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscTypeIncorrect", "'ComposedDiscTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscTypeInconsistent", "'ComposedDiscTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscRequiredInconsistent", "'ComposedDiscRequiredInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+
+        for(Map.Entry<String, String> entry : hm.entrySet()) {
+            String modelName = entry.getKey();
+            String errorMessageExpected = entry.getValue();
+
+            Schema sc = openAPI.getComponents().getSchemas().get(modelName);
+
+            try {
+                codegen.fromModel(modelName, sc);
+                Assert.assertTrue(false, "A RuntimeException should have been thrown when processing "+modelName+ " but it was not");
+            } catch (RuntimeException re) {
+                Assert.assertEquals(re.getMessage(), errorMessageExpected);
+            }
+        }
+    }
+
+    @Test
+    public void testComposedSchemaAnyOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/anyOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        String modelName;
+        Schema sc;
+        CodegenModel cm;
+        java.util.LinkedHashSet hs;
+        String mn;
+
+        // inline anyOf models work because the inline schemas are turned into $refs
+        modelName = "FruitInlineDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "FruitInlineDisc_anyOf";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        mn = "FruitInlineDisc_anyOf_1";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // inline anyOf with inline anyOf model doesn't work because we have null $refs and we throw an exception
+        final String fmodelName = "FruitInlineInlineDisc";
+        final Schema fsc = openAPI.getComponents().getSchemas().get(fmodelName);
+        Assert.assertThrows(() -> codegen.fromModel(fmodelName, fsc));
+
+        // ref anyOf models with discriminator in properties in those models
+        modelName = "FruitReqDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in allOf in those models
+        modelName = "FruitAllOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in anyOf in those models
+        modelName = "FruitAnyOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in anyOf in those models
+        modelName = "FruitAnyOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in the grandparent schemas of those anyof models
+        modelName = "FruitGrandparentDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+    }
+
+    @Test
+    public void testComposedSchemaOneOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        String modelName;
+        Schema sc;
+        CodegenModel cm;
+        java.util.LinkedHashSet hs;
+        String mn;
+
+        // inline oneOf models work because the inline schemas are turned into $refs
+        modelName = "FruitInlineDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "FruitInlineDisc_oneOf";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        mn = "FruitInlineDisc_oneOf_1";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // inline oneOf with inline oneOf model doesn't work because we have null $refs and we throw an exception
+        final String fmodelName = "FruitInlineInlineDisc";
+        final Schema fsc = openAPI.getComponents().getSchemas().get(fmodelName);
+        Assert.assertThrows(() -> codegen.fromModel(fmodelName, fsc));
+
+        // ref oneOf models with discriminator in properties in those models
+        modelName = "FruitReqDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in allOf in those models
+        modelName = "FruitAllOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in anyOf in those models
+        modelName = "FruitAnyOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in oneOf in those models
+        modelName = "FruitOneOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleOneOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaOneOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in the grandparent schemas of those oneof models
+        modelName = "FruitGrandparentDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+    }
+
+    @Test
+    public void testComposedSchemaMyPetsOneOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        String path = "/mypets";
+
+        Operation operation = openAPI.getPaths().get(path).getGet();
+        CodegenOperation codegenOperation = codegen.fromOperation(path, "GET", operation, null);
+        verifyMyPetsDiscriminator(codegenOperation.discriminator);
+
+        Schema pet = openAPI.getComponents().getSchemas().get("MyPets");
+        CodegenModel petModel = codegen.fromModel("MyPets", pet);
+        verifyMyPetsDiscriminator(petModel.discriminator);
+    }
+
+    @Test
+    public void testComposedSchemaAllOfHierarchy(){
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        Schema pet = openAPI.getComponents().getSchemas().get("Lizard");
+        CodegenModel petModel = codegen.fromModel("Lizard", pet);
+        verifyLizardDiscriminator(petModel.discriminator);
+
+        pet = openAPI.getComponents().getSchemas().get("Reptile");
+        petModel = codegen.fromModel("Reptile", pet);
+        verifyReptileDiscriminator(petModel.discriminator);
+    }
+
+    private void verifyLizardDiscriminator(CodegenDiscriminator discriminator) {
+        CodegenDiscriminator test = new CodegenDiscriminator();
+        String prop = "petType";
+        test.setPropertyName(prop);
+        test.setPropertyBaseName(prop);
+        test.setMapping(null);
+        test.setMappedModels(new HashSet<>());
+        assertEquals(discriminator, test);
+    }
+
+    private void verifyReptileDiscriminator(CodegenDiscriminator discriminator) {
+        CodegenDiscriminator test = new CodegenDiscriminator();
+        String prop = "petType";
+        test.setPropertyName(prop);
+        test.setPropertyBaseName(prop);
+        test.setMapping(null);
+        test.setMappedModels(new HashSet<CodegenDiscriminator.MappedModel>(){{
+            add(new CodegenDiscriminator.MappedModel("Snake", "Snake"));
+            add(new CodegenDiscriminator.MappedModel("Lizard", "Lizard"));
+        }});
+        assertEquals(discriminator, test);
+    }
+
+    private void verifyMyPetsDiscriminator(CodegenDiscriminator discriminator) {
+        CodegenDiscriminator test = new CodegenDiscriminator();
+        String prop = "petType";
+        test.setPropertyName(prop);
+        test.setPropertyBaseName(prop);
+        test.setMapping(null);
+        test.setMappedModels(new HashSet<CodegenDiscriminator.MappedModel>(){{
+            add(new CodegenDiscriminator.MappedModel("Cat", "Cat"));
+            add(new CodegenDiscriminator.MappedModel("Lizard", "Lizard"));
+        }});
+        assertEquals(discriminator, test);
+    }
+
+    public CodegenModel getModel(List<Object> allModels, String modelName) {
+        for (Object obj: allModels) {
+            HashMap<String, Object> hm = (HashMap<String, Object>) obj;
+            CodegenModel cm = (CodegenModel) hm.get("model");
+            if (modelName.equals(cm.name)) {
+                return cm;
+            }
+        }
+        return null;
+    }
+
+    @Test
+    public void verifyXDiscriminatorValue() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/2_0/x-discriminator-value.yaml");
+        final DefaultCodegen config = new DefaultCodegen();
+        config.setOpenAPI(openAPI);
+
+        String modelName;
+        CodegenDiscriminator discriminator;
+        Schema sc;
+        CodegenModel cm;
+
+        Boolean dryRun = Boolean.TRUE;
+        final DefaultGenerator generator = new DefaultGenerator(dryRun);
+        generator.openAPI = openAPI;
+        generator.config = config;
+        generator.configureGeneratorProperties();
+
+        // for us to check a model's children we need to run generator.generateModels
+        // because children are assigned in config.updateAllModels which is invoked in generator.generateModels
+        List<File> files = new ArrayList<>();
+        List<String> filteredSchemas = ModelUtils.getSchemasUsedOnlyInFormParam(openAPI);
+        List<Object> allModels = new ArrayList<>();
+        generator.generateModels(files, allModels, filteredSchemas);
+
+        // check that the model's children contain the x-discriminator-values
+        modelName = "BaseObj";
+        cm = getModel(allModels, modelName);
+        List<String> excpectedDiscriminatorValues = new ArrayList<>(Arrays.asList("daily", "sub-obj"));
+        ArrayList<String> xDiscriminatorValues = new ArrayList<>();
+        for (CodegenModel child: cm.children) {
+            xDiscriminatorValues.add((String) child.vendorExtensions.get("x-discriminator-value"));
+        }
+        assertEquals(xDiscriminatorValues, excpectedDiscriminatorValues);
+
+        // check that the discriminator's MappedModels also contains the x-discriminator-values
+        discriminator = new CodegenDiscriminator();
+        String prop = "object_type";
+        discriminator.setPropertyName(config.toVarName(prop));
+        discriminator.setPropertyBaseName(prop);
+        discriminator.setMapping(null);
+        discriminator.setMappedModels(new HashSet<CodegenDiscriminator.MappedModel>(){{
+            add(new CodegenDiscriminator.MappedModel("DailySubObj", "DailySubObj"));
+            add(new CodegenDiscriminator.MappedModel("SubObj", "SubObj"));
+            add(new CodegenDiscriminator.MappedModel("daily", "DailySubObj"));
+            add(new CodegenDiscriminator.MappedModel("sub-obj", "SubObj"));
+        }});
+        assertEquals(cm.discriminator, discriminator);
+    }
+
+
     @Test
     public void testAllOfSingleRefNoOwnProps() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/2_0/composed-allof.yaml");
@@ -1025,6 +1592,8 @@ private void verifyPersonDiscriminator(CodegenDiscriminator discriminator) {
         test.getMapping().put("c", "Child");
         test.getMappedModels().add(new CodegenDiscriminator.MappedModel("a", "Adult"));
         test.getMappedModels().add(new CodegenDiscriminator.MappedModel("c", "Child"));
+        test.getMappedModels().add(new CodegenDiscriminator.MappedModel("Adult", "Adult"));
+        test.getMappedModels().add(new CodegenDiscriminator.MappedModel("Child", "Child"));
         Assert.assertEquals(discriminator, test);
     }
 
@@ -1131,8 +1700,7 @@ public void modelDoNotContainInheritedVars() {
         DefaultCodegen codegen = new DefaultCodegen();
         codegen.supportsInheritance = true;
 
-        OpenAPI openAPI = new OpenAPIParser()
-                .readLocation("src/test/resources/3_0/generic.yaml", null, new ParseOptions()).getOpenAPI();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/generic.yaml");
         codegen.setOpenAPI(openAPI);
 
         CodegenModel codegenModel = codegen.fromModel("Dog", openAPI.getComponents().getSchemas().get("Dog"));
@@ -1161,8 +1729,7 @@ public void modelWithPrefixDoNotContainInheritedVars() {
         codegen.supportsInheritance = true;
         codegen.setModelNamePrefix("prefix");
 
-        OpenAPI openAPI = new OpenAPIParser()
-                .readLocation("src/test/resources/3_0/generic.yaml", null, new ParseOptions()).getOpenAPI();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/generic.yaml");
         codegen.setOpenAPI(openAPI);
 
         CodegenModel codegenModel = codegen.fromModel("Dog", openAPI.getComponents().getSchemas().get("Dog"));
@@ -1176,8 +1743,7 @@ public void modelWithSuffixDoNotContainInheritedVars() {
         codegen.supportsInheritance = true;
         codegen.setModelNameSuffix("suffix");
 
-        OpenAPI openAPI = new OpenAPIParser()
-                .readLocation("src/test/resources/3_0/generic.yaml", null, new ParseOptions()).getOpenAPI();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/generic.yaml");
         codegen.setOpenAPI(openAPI);
 
         CodegenModel codegenModel = codegen.fromModel("Dog", openAPI.getComponents().getSchemas().get("Dog"));
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java
index 17fddc4cfb6b..45b03efcccef 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java
@@ -70,6 +70,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ENSURE_UNIQUE_PARAMS, "false")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     
     }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java
index 226389505b0a..79cf084234f1 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java
@@ -62,6 +62,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(DartClientCodegen.SUPPORT_DART2, "false")
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java
index da24d2e195a7..9e54e028f7ff 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java
@@ -67,6 +67,7 @@ public Map<String, String> createOptions() {
                 .put(DartDioClientCodegen.SUPPORT_DART2, "false")
                 .put(DartDioClientCodegen.DATE_LIBRARY, DATE_LIBRARY)
                 .put(DartDioClientCodegen.NULLABLE_FIELDS, NULLABLE_FIELDS)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java
index 0a0f86e4eeb7..f6efa94aa517 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java
@@ -43,6 +43,7 @@ public Map<String, String> createOptions() {
                 .put("licenseHeader", "# Copyright 2017 Me\n#\n# Licensed under the Apache License")
                 .put(CodegenConstants.PACKAGE_NAME, "yay_pets")
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java
index 15a466650963..f883ebbed197 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java
@@ -48,6 +48,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(HaskellServantCodegen.PROP_SERVE_STATIC, HaskellServantCodegen.PROP_SERVE_STATIC_DEFAULT.toString())
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java
index b1aed3e446eb..245957be4076 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java
@@ -58,6 +58,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.HIDE_GENERATION_TIMESTAMP, "true")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java
index 8f2c1d574ff9..97ad8132ce43 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java
@@ -57,6 +57,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ARTIFACT_VERSION, ARTIFACT_VERSION_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java
index faf3992c99df..a3f32f9b4a00 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java
@@ -42,6 +42,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ENSURE_UNIQUE_PARAMS, ENSURE_UNIQUE_PARAMS_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java
index 98c1ded49d28..4bf91932a3f0 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java
@@ -60,6 +60,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(PhpSlim4ServerCodegen.PSR7_IMPLEMENTATION, PSR7_IMPLEMENTATION_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java
index 70eed81c9e2f..537b7b10c664 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java
@@ -57,6 +57,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ENSURE_UNIQUE_PARAMS, ENSURE_UNIQUE_PARAMS_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java
index dce16e7245da..09bd0dceabc1 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java
@@ -66,6 +66,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(CodegenConstants.LIBRARY, LIBRARY)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java
index f9ac4d5ee3b4..4b982932b98a 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java
@@ -55,6 +55,7 @@ public Map<String, String> createOptions() {
                 .put("mainPackage", MAIN_PACKAGE_VALUE)
                 .put(CodegenConstants.MODEL_PROPERTY_NAMING, MODEL_PROPERTY_NAMING)
                 .put("dateLibrary", DATE_LIBRARY)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java
index c128ea1bba77..11825e2ec129 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java
@@ -52,6 +52,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put("dateLibrary", DATE_LIBRARY)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java
index 6e496e915af6..d83863cd7391 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java
@@ -79,6 +79,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.HIDE_GENERATION_TIMESTAMP, "true")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java
index 87c2ecbebd3f..aa2d61f28294 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java
@@ -81,6 +81,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.HIDE_GENERATION_TIMESTAMP, "true")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java
index 3f85681caa68..d5cd8cbe38e8 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java
@@ -80,6 +80,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(CodegenConstants.API_NAME_PREFIX, "")
                 .put(CodegenConstants.LIBRARY, LIBRARY_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java
index 5635465a6322..51b62748e3c5 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java
@@ -81,6 +81,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(TypeScriptAngularClientCodegen.FILE_NAMING, FILE_NAMING_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java
index 2ab399a12bb1..1e008de1ed16 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java
@@ -53,6 +53,7 @@ public Map<String, String> createOptions() {
                 .put(CodegenConstants.MODEL_PROPERTY_NAMING, MODEL_PROPERTY_NAMING_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java
index 9c72ca44ab9f..58b5aa61826a 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java
@@ -59,6 +59,7 @@ public Map<String, String> createOptions() {
                 .put(TypeScriptAureliaClientCodegen.SNAPSHOT, Boolean.FALSE.toString())
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java
index 196e220fb328..7bec81c9ae36 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java
@@ -66,6 +66,7 @@ public Map<String, String> createOptions() {
                 .put(TypeScriptFetchClientCodegen.TYPESCRIPT_THREE_PLUS, TYPESCRIPT_THREE_PLUS)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java
index 23da17ea1c49..a2dc76d63f41 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java
@@ -63,6 +63,7 @@ public Map<String, String> createOptions() {
                 .put(TypeScriptAngularClientCodegen.NPM_REPOSITORY, NPM_REPOSITORY)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
index 7191f6e5ee0c..cdde6ddc8f37 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
@@ -363,6 +363,7 @@ public void oneOfTest() {
     public void allOfTest() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf.yaml");
         final RubyClientCodegen codegen = new RubyClientCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
         codegen.setModuleName("OnlinePetstore");
 
         final Schema schema = openAPI.getComponents().getSchemas().get("Person");
@@ -372,10 +373,29 @@ public void allOfTest() {
 
         CodegenDiscriminator codegenDiscriminator = person.getDiscriminator();
         Set<CodegenDiscriminator.MappedModel> mappedModels = new LinkedHashSet<CodegenDiscriminator.MappedModel>();
-        CodegenDiscriminator.MappedModel adult = new CodegenDiscriminator.MappedModel("a", "Adult");
-        mappedModels.add(adult);
-        CodegenDiscriminator.MappedModel child = new CodegenDiscriminator.MappedModel("c", "Child");
-        mappedModels.add(child);
+        mappedModels.add(new CodegenDiscriminator.MappedModel("a", "Adult"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("c", "Child"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("Adult", "Adult"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("Child", "Child"));
+        Assert.assertEquals(codegenDiscriminator.getMappedModels(), mappedModels);
+    }
+
+    @Test(description = "test allOf (OAS3)")
+    public void allOfTestLegacy() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf.yaml");
+        final RubyClientCodegen codegen = new RubyClientCodegen();
+        // codegen.discriminatorExplicitMappingVerbose == false by default
+        codegen.setModuleName("OnlinePetstore");
+
+        final Schema schema = openAPI.getComponents().getSchemas().get("Person");
+        codegen.setOpenAPI(openAPI);
+        CodegenModel person = codegen.fromModel("Person", schema);
+        Assert.assertNotNull(person);
+
+        CodegenDiscriminator codegenDiscriminator = person.getDiscriminator();
+        Set<CodegenDiscriminator.MappedModel> mappedModels = new LinkedHashSet<CodegenDiscriminator.MappedModel>();
+        mappedModels.add(new CodegenDiscriminator.MappedModel("a", "Adult"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("c", "Child"));
         Assert.assertEquals(codegenDiscriminator.getMappedModels(), mappedModels);
     }
 
diff --git a/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml b/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml
index 7397e6c5d5fc..ba8906a1a2dd 100644
--- a/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml
+++ b/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml
@@ -2077,12 +2077,11 @@ definitions:
     properties:
       pet_type:
         type: string
+    discriminator: pet_type
   ParentPet:
     type: object
     allOf:
     - $ref: '#/definitions/GrandparentAnimal'
-    - type: object
-      discriminator: pet_type
   ChildCat:
     allOf:
     - $ref: '#/definitions/ParentPet'
diff --git a/modules/openapi-generator/src/test/resources/2_0/x-discriminator-value.yaml b/modules/openapi-generator/src/test/resources/2_0/x-discriminator-value.yaml
new file mode 100644
index 000000000000..9dc4dea3e293
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/2_0/x-discriminator-value.yaml
@@ -0,0 +1,66 @@
+swagger: '2.0'
+info:
+  description: 'blah'
+  version: 1.0.0
+  title: sample spec
+host: fake.site.com
+tags: []
+schemes:
+  - https
+paths:
+  /numberdata:
+    post:
+      operationId: getNumberHolder
+      consumes:
+        - application/json
+      produces:
+        - application/json
+      parameters: []
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/BaseObj'
+securityDefinitions: {}
+definitions:
+  BaseObj:
+    type: object
+    discriminator: object_type
+    required:
+      - id
+      - object_type
+    properties:
+      id:
+        type: integer
+        format: int64
+      object_type:
+        type: string
+  SubObjType:
+    type: string
+    enum:
+      - daily
+      - monthly
+      - quarterly
+      - yearly
+  SubObj:
+    x-discriminator-value: sub-obj
+    allOf:
+      - $ref: '#/definitions/BaseObj'
+      - type: object
+        discriminator: sub_obj_type
+        required:
+          - sub_obj_type
+        properties:
+          sub_obj_type:
+            $ref: '#/definitions/SubObjType'
+          name:
+            type: string
+  DailySubObj:
+    x-discriminator-value: daily
+    allOf:
+      - $ref: '#/definitions/SubObj'
+      - type: object
+        properties:
+          day_of_month:
+            type: integer
+            format: int32
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/3_0/allOf_composition_discriminator.yaml b/modules/openapi-generator/src/test/resources/3_0/allOf_composition_discriminator.yaml
new file mode 100644
index 000000000000..efeaa5fd02e9
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/allOf_composition_discriminator.yaml
@@ -0,0 +1,103 @@
+openapi: 3.0.2
+info:
+  title: OAI Specification example for Polymorphism
+  version: 1.0.0
+paths:
+  /pet:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Pet'
+  /reptile:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Reptile'
+  /mypets:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/MyPets'
+components:
+  schemas:
+    Pet:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+      discriminator:
+        propertyName: petType
+    Cat:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            name:
+              type: string
+    Reptile:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+    Dog:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            bark:
+              type: string
+    Lizard:
+      allOf:
+        - $ref: '#/components/schemas/Reptile'
+        - type: object
+          properties:
+            lovesRocks:
+              type: boolean
+    Snake:
+      allOf:
+        - $ref: '#/components/schemas/Reptile'
+        - type: object
+          properties:
+            hasLegs:
+              type: boolean
+    MyPets:
+      oneOf:
+        - $ref: '#/components/schemas/Cat'
+        - $ref: '#/components/schemas/Lizard'
+      discriminator:
+        propertyName: petType
+        # per https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#discriminatorObject
+        # this discriminator must be included to use it as a hint to pick a schema
+    MyPetsNoDisc:
+      oneOf:
+        - $ref: '#/components/schemas/Cat'
+        - $ref: '#/components/schemas/Lizard'
+    A:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+      discriminator:
+        propertyName: petType
+        mapping:
+          b: '#/components/schemas/B'
+    B:
+      allOf:
+        - $ref: '#/components/schemas/A'
+    C:
+      allOf:
+        - $ref: '#/components/schemas/B'
diff --git a/modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminator.yaml b/modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminator.yaml
new file mode 100644
index 000000000000..72fa6abbb7d1
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminator.yaml
@@ -0,0 +1,244 @@
+openapi: 3.0.1
+info:
+   title: fruity
+   version: 0.0.1
+paths:
+   /:
+      get:
+         responses:
+            '200':
+               description: desc
+               content:
+                  application/json:
+                     schema:
+                        $ref: '#/components/schemas/FruitAllOfDisc'
+components:
+   schemas:
+    FruitType:
+      properties:
+        fruitType:
+          type: string
+      required:
+      - fruitType
+    FruitInlineDisc:
+      anyOf:
+        - type: object
+          required:
+            - seeds
+            - fruitType
+          properties:
+            seeds:
+              type: integer
+            fruitType:
+              type: string
+        - type: object
+          required:
+            - length
+            - fruitType
+          properties:
+            length:
+              type: integer
+            fruitType:
+              type: string
+      discriminator:
+        propertyName: fruitType
+    FruitInlineInlineDisc:
+      anyOf:
+        - type: object
+          required:
+            - seeds
+          properties:
+            seeds:
+              type: integer
+          anyOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+        - type: object
+          required:
+            - length
+          properties:
+            length:
+              type: integer
+          anyOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+      discriminator:
+        propertyName: fruitType
+    FruitReqDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleReqDisc'
+        - $ref: '#/components/schemas/BananaReqDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleReqDisc:
+      type: object
+      required:
+        - seeds
+        - fruitType
+      properties:
+        seeds:
+          type: integer
+        fruitType:
+          type: string
+    BananaReqDisc:
+      type: object
+      required:
+        - length
+        - fruitType
+      properties:
+        length:
+          type: integer
+        fruitType:
+          type: string
+    FruitAllOfDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleAllOfDisc'
+        - $ref: '#/components/schemas/BananaAllOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAllOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAllOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitAnyOfDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleAnyOfDisc'
+        - $ref: '#/components/schemas/BananaAnyOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAnyOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAnyOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitGrandparentDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleGrandparentDisc'
+        - $ref: '#/components/schemas/BananaGrandparentDisc'
+      discriminator:
+        propertyName: fruitType
+    Parent:
+      type: object
+      allOf:
+        # the FruitType schema is a grandparent of AppleGrandparentDisc + BananaGrandparentDisc
+        - $ref: '#/components/schemas/FruitType'
+    AppleGrandparentDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    BananaGrandparentDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    ComposedDiscMissingNoProperties:
+      anyOf:
+        - $ref: '#/components/schemas/DiscMissingNoProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingNoProperties:
+      type: object
+    ComposedDiscMissingFromProperties:
+      anyOf:
+        - $ref: '#/components/schemas/DiscMissingFromProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingFromProperties:
+      type: object
+      properties:
+        length:
+          type: integer
+    ComposedDiscOptionalTypeCorrect:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeCorrect:
+      type: object
+      properties:
+        fruitType:
+          type: string
+    ComposedDiscOptionalTypeIncorrect:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+    ComposedDiscOptionalTypeInconsistent:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscTypeIncorrect:
+      anyOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+      required:
+        - fruitType
+    ComposedDiscTypeInconsistent:
+      anyOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscRequiredInconsistent:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/3_0/oneOfDiscriminator.yaml b/modules/openapi-generator/src/test/resources/3_0/oneOfDiscriminator.yaml
new file mode 100644
index 000000000000..e9a342980749
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/oneOfDiscriminator.yaml
@@ -0,0 +1,268 @@
+openapi: 3.0.1
+info:
+   title: fruity
+   version: 0.0.1
+paths:
+   /:
+      get:
+         responses:
+            '200':
+               description: desc
+               content:
+                  application/json:
+                     schema:
+                        $ref: '#/components/schemas/FruitAllOfDisc'
+components:
+   schemas:
+    FruitType:
+      properties:
+        fruitType:
+          type: string
+      required:
+      - fruitType
+    FruitInlineDisc:
+      oneOf:
+        - type: object
+          required:
+            - seeds
+            - fruitType
+          properties:
+            seeds:
+              type: integer
+            fruitType:
+              type: string
+        - type: object
+          required:
+            - length
+            - fruitType
+          properties:
+            length:
+              type: integer
+            fruitType:
+              type: string
+      discriminator:
+        propertyName: fruitType
+    FruitInlineInlineDisc:
+      oneOf:
+        - type: object
+          required:
+            - seeds
+          properties:
+            seeds:
+              type: integer
+          oneOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+        - type: object
+          required:
+            - length
+          properties:
+            length:
+              type: integer
+          oneOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+      discriminator:
+        propertyName: fruitType
+    FruitReqDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleReqDisc'
+        - $ref: '#/components/schemas/BananaReqDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleReqDisc:
+      type: object
+      required:
+        - seeds
+        - fruitType
+      properties:
+        seeds:
+          type: integer
+        fruitType:
+          type: string
+    BananaReqDisc:
+      type: object
+      required:
+        - length
+        - fruitType
+      properties:
+        length:
+          type: integer
+        fruitType:
+          type: string
+    FruitAllOfDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleAllOfDisc'
+        - $ref: '#/components/schemas/BananaAllOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAllOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAllOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitAnyOfDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleAnyOfDisc'
+        - $ref: '#/components/schemas/BananaAnyOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAnyOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAnyOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitOneOfDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleOneOfDisc'
+        - $ref: '#/components/schemas/BananaOneOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleOneOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      oneOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaOneOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      oneOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitGrandparentDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleGrandparentDisc'
+        - $ref: '#/components/schemas/BananaGrandparentDisc'
+      discriminator:
+        propertyName: fruitType
+    Parent:
+      type: object
+      allOf:
+        # the FruitType schema is a grandparent of AppleGrandparentDisc + BananaGrandparentDisc
+        - $ref: '#/components/schemas/FruitType'
+    AppleGrandparentDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    BananaGrandparentDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    ComposedDiscMissingNoProperties:
+      oneOf:
+        - $ref: '#/components/schemas/DiscMissingNoProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingNoProperties:
+      type: object
+    ComposedDiscMissingFromProperties:
+      oneOf:
+        - $ref: '#/components/schemas/DiscMissingFromProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingFromProperties:
+      type: object
+      properties:
+        length:
+          type: integer
+    ComposedDiscOptionalTypeCorrect:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeCorrect:
+      type: object
+      properties:
+        fruitType:
+          type: string
+    ComposedDiscOptionalTypeIncorrect:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+    ComposedDiscOptionalTypeInconsistent:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscTypeIncorrect:
+      oneOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+      required:
+        - fruitType
+    ComposedDiscTypeInconsistent:
+      oneOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscRequiredInconsistent:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
diff --git a/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java
index 00db7a1b7b6d..ff1964caa4bb 100644
--- a/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java
@@ -43,7 +43,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java
index b5b4f315c165..345d77346315 100644
--- a/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java
@@ -41,7 +41,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java
index 1367d6dd7886..4b6c177d34a2 100644
--- a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java
@@ -34,7 +34,7 @@
 public class Animal implements Parcelable {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f40..cea2ff5988d7 100644
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java
index 57dad620ef0a..0390cab3e8c3 100644
--- a/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java
@@ -45,7 +45,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java
index bb64354ab52e..4cbc678b5321 100644
--- a/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java
@@ -35,7 +35,7 @@
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java
index af9c0df70387..87a9c706f4a9 100644
--- a/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java
@@ -48,7 +48,7 @@
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
   @XmlElement(name = "className")
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   @XmlElement(name = "color")
diff --git a/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f40..cea2ff5988d7 100644
--- a/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java
index 38b0a1b2f159..e93cac2705d0 100644
--- a/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java
@@ -44,7 +44,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java
index 38b0a1b2f159..e93cac2705d0 100644
--- a/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java
@@ -44,7 +44,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java
index 38b0a1b2f159..e93cac2705d0 100644
--- a/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java
@@ -44,7 +44,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f40..cea2ff5988d7 100644
--- a/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f40..cea2ff5988d7 100644
--- a/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f40..cea2ff5988d7 100644
--- a/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483bd..bbadf265ba6b 100644
--- a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/python-asyncio/petstore_api/api_client.py b/samples/client/petstore/python-asyncio/petstore_api/api_client.py
index bed70584efb9..8aae783bfc3b 100644
--- a/samples/client/petstore/python-asyncio/petstore_api/api_client.py
+++ b/samples/client/petstore/python-asyncio/petstore_api/api_client.py
@@ -625,9 +625,12 @@ def __deserialize_model(self, data, klass):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -641,7 +644,7 @@ def __deserialize_model(self, data, klass):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/animal.py b/samples/client/petstore/python-experimental/petstore_api/models/animal.py
index 45058ec7612f..39dd9789ff8b 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/animal.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/animal.py
@@ -90,12 +90,13 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return {
-            'class_name': {
-                'Cat': cat.Cat,
-                'Dog': dog.Dog,
-            },
+        val = {
+            'Cat': cat.Cat,
+            'Dog': dog.Dog,
         }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/cat.py b/samples/client/petstore/python-experimental/petstore_api/models/cat.py
index d40464eaf0e9..3f3c2384ec22 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/cat.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/cat.py
@@ -91,7 +91,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -194,3 +198,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py b/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py
index b83986bd68a8..e7894c9c7af4 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py
@@ -90,7 +90,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -191,3 +195,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py b/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py
index da568bd7d271..8544773e8843 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py
@@ -90,7 +90,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -191,3 +195,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py b/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py
index 62fa11f26e80..681e99ae6665 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py
@@ -90,7 +90,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -191,3 +195,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/dog.py b/samples/client/petstore/python-experimental/petstore_api/models/dog.py
index 69af821b27e2..5d5712d428e9 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/dog.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/dog.py
@@ -91,7 +91,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -194,3 +198,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py b/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py
index af25951ed73a..db7e6f33887d 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py
@@ -29,6 +29,26 @@
     str,
     validate_get_composed_info,
 )
+try:
+    from petstore_api.models import child_cat
+except ImportError:
+    child_cat = sys.modules[
+        'petstore_api.models.child_cat']
+try:
+    from petstore_api.models import child_dog
+except ImportError:
+    child_dog = sys.modules[
+        'petstore_api.models.child_dog']
+try:
+    from petstore_api.models import child_lizard
+except ImportError:
+    child_lizard = sys.modules[
+        'petstore_api.models.child_lizard']
+try:
+    from petstore_api.models import parent_pet
+except ImportError:
+    parent_pet = sys.modules[
+        'petstore_api.models.parent_pet']
 
 
 class GrandparentAnimal(ModelNormal):
@@ -79,7 +99,15 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+            'ChildCat': child_cat.ChildCat,
+            'ChildDog': child_dog.ChildDog,
+            'ChildLizard': child_lizard.ChildLizard,
+            'ParentPet': parent_pet.ParentPet,
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -134,3 +162,16 @@ def __init__(self, pet_type, _check_type=True, _from_server=False, _path_to_item
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py b/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py
index cdb96676c555..e7f2a6fb63f9 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py
@@ -99,13 +99,14 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return {
-            'pet_type': {
-                'ChildCat': child_cat.ChildCat,
-                'ChildDog': child_dog.ChildDog,
-                'ChildLizard': child_lizard.ChildLizard,
-            },
+        val = {
+            'ChildCat': child_cat.ChildCat,
+            'ChildDog': child_dog.ChildDog,
+            'ChildLizard': child_lizard.ChildLizard,
         }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
diff --git a/samples/client/petstore/python-tornado/petstore_api/api_client.py b/samples/client/petstore/python-tornado/petstore_api/api_client.py
index 6b9c738128fd..328c1a70e10e 100644
--- a/samples/client/petstore/python-tornado/petstore_api/api_client.py
+++ b/samples/client/petstore/python-tornado/petstore_api/api_client.py
@@ -626,9 +626,12 @@ def __deserialize_model(self, data, klass):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -642,7 +645,7 @@ def __deserialize_model(self, data, klass):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/samples/client/petstore/python/petstore_api/api_client.py b/samples/client/petstore/python/petstore_api/api_client.py
index c0564c598f13..a80084e04b0f 100644
--- a/samples/client/petstore/python/petstore_api/api_client.py
+++ b/samples/client/petstore/python/petstore_api/api_client.py
@@ -624,9 +624,12 @@ def __deserialize_model(self, data, klass):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -640,7 +643,7 @@ def __deserialize_model(self, data, klass):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py
index 45058ec7612f..39dd9789ff8b 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py
@@ -90,12 +90,13 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return {
-            'class_name': {
-                'Cat': cat.Cat,
-                'Dog': dog.Dog,
-            },
+        val = {
+            'Cat': cat.Cat,
+            'Dog': dog.Dog,
         }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py
index 92076d35c068..c3641a6862b9 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py
@@ -96,7 +96,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -200,3 +204,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py
index 69af821b27e2..5d5712d428e9 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py
@@ -91,7 +91,11 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -194,3 +198,16 @@ def _composed_schemas():
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py
index 303838fd7d4b..d5ee114fe25f 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py
@@ -97,12 +97,13 @@ def openapi_types():
 
     @staticmethod
     def discriminator():
-        return {
-            'class_name': {
-                'whale': whale.Whale,
-                'zebra': zebra.Zebra,
-            },
+        val = {
+            'whale': whale.Whale,
+            'zebra': zebra.Zebra,
         }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
diff --git a/samples/openapi3/client/petstore/python/petstore_api/api_client.py b/samples/openapi3/client/petstore/python/petstore_api/api_client.py
index c0564c598f13..a80084e04b0f 100644
--- a/samples/openapi3/client/petstore/python/petstore_api/api_client.py
+++ b/samples/openapi3/client/petstore/python/petstore_api/api_client.py
@@ -624,9 +624,12 @@ def __deserialize_model(self, data, klass):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -640,7 +643,7 @@ def __deserialize_model(self, data, klass):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)