From 4c62b345815890d96cbc769fc9f41d95da83035a Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Wed, 3 Mar 2021 20:21:59 +0000
Subject: [PATCH 1/9] Fix api-client deserialization for json_serializable

---
 .../src/main/resources/dart2/api.mustache     |  32 ++--
 .../main/resources/dart2/api_client.mustache  |  24 +--
 .../main/resources/dart2/api_helper.mustache  |   3 +-
 .../lib/api/another_fake_api.dart             |   6 +-
 .../lib/api/default_api.dart                  |   6 +-
 .../lib/api/fake_api.dart                     |  54 +++----
 .../lib/api/fake_classname_tags123_api.dart   |   6 +-
 .../lib/api/pet_api.dart                      |  44 +++---
 .../lib/api/store_api.dart                    |  20 +--
 .../lib/api/user_api.dart                     |  24 +--
 .../lib/api_client.dart                       | 148 +-----------------
 .../lib/api_helper.dart                       |  15 +-
 12 files changed, 117 insertions(+), 265 deletions(-)

diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index ad30ec2cdf03..af852b117566 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -61,7 +61,7 @@ class {{{classname}}} {
     {{/allParams}}
 
   {{/hasParams}}
-    final path = '{{{path}}}'{{#pathParams}}
+    final path = r'{{{path}}}'{{#pathParams}}
       .replaceAll('{' + '{{{baseName}}}' + '}', {{{paramName}}}.toString()){{/pathParams}};
 
     Object postBody{{#bodyParam}} = {{{paramName}}}{{/bodyParam}};
@@ -185,21 +185,23 @@ class {{{classname}}} {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      {{#isArray}}
-      return (apiClient.deserialize(_decodeBodyBytes(response), '{{{returnType}}}') as List)
-        .cast<{{{returnBaseType}}}>()
-        .{{#uniqueItems}}toSet(){{/uniqueItems}}{{^uniqueItems}}toList(growable: false){{/uniqueItems}};
-      {{/isArray}}
-      {{^isArray}}
-        {{#isMap}}
-      return {{{returnType}}}.from(apiClient.deserialize(_decodeBodyBytes(response), '{{{returnType}}}'));
-        {{/isMap}}
-        {{^isMap}}
-      return apiClient.deserialize(_decodeBodyBytes(response), '{{{returnType}}}') as {{{returnType}}};
-        {{/isMap}}
-      {{/isArray}}
+    {{#isArray}}
+      final l = json.decode(response.body);
+      return {{{returnType}}}.from(l.map((model) => Pet.fromJson(model)));
+    {{/isArray}}
+    {{^isArray}}
+    {{#isMap}}
+      return {{{returnType}}}.from(json.decode(response.body));
+    {{/isMap}}
+    {{^isMap}}
+      return {{{returnType}}}.fromJson(json.decode(response.body));
+    {{/isMap}}
+    {{/isArray}}
+    {{#isString}}
+      return json.decode(response.body);
+    {{/isString}}
     }
-    return null;
+    return Future.value(null);
     {{/returnType}}
   }
   {{/operation}}
diff --git a/modules/openapi-generator/src/main/resources/dart2/api_client.mustache b/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
index e231ff72859d..a5d3b0948e7c 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
@@ -56,17 +56,6 @@ class ApiClient {
   Map<String, Authentication> get authentications =>
       Map.unmodifiable(_authentications);
 
-  dynamic deserialize(String json, String targetType, {bool growable}) {
-    // Remove all spaces.  Necessary for reg expressions as well.
-    targetType = targetType.replaceAll(' ', '');
-
-    return targetType == 'String'
-      ? json
-      : _deserialize(jsonDecode(json), targetType, growable: true == growable);
-  }
-
-  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
-
   T getAuthentication<T extends Authentication>(String name) {
     final authentication = _authentications[name];
     return authentication is T ? authentication : null;
@@ -159,6 +148,7 @@ class ApiClient {
     throw ApiException(HttpStatus.badRequest, 'Invalid HTTP operation: $method $path',);
   }
 
+{{#native_serialization}}
   dynamic _deserialize(dynamic value, String targetType, {bool growable}) {
     try {
       switch (targetType) {
@@ -216,6 +206,18 @@ class ApiClient {
     throw ApiException(HttpStatus.internalServerError, 'Could not find a suitable class for deserialization',);
   }
 
+  dynamic deserialize(String json, String targetType, {bool growable}) {
+    // Remove all spaces.  Necessary for reg expressions as well.
+    targetType = targetType.replaceAll(' ', '');
+
+  return targetType == 'String'
+    ? json
+    : _deserialize(jsonDecode(json), targetType, growable: true == growable);
+  }
+{{/native_serialization}}
+
+  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
+
   /// Update query and header parameters based on authentication settings.
   /// @param authNames The authentications to apply
   void _updateParamsForAuth(
diff --git a/modules/openapi-generator/src/main/resources/dart2/api_helper.mustache b/modules/openapi-generator/src/main/resources/dart2/api_helper.mustache
index 823829acd9c8..8e70b9920bfb 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api_helper.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api_helper.mustache
@@ -53,8 +53,7 @@ String parameterToString(dynamic value) {
     {{#model}}
       {{#isEnum}}
   if (value is {{{classname}}}) {
-{{#native_serialization}}    return {{{classname}}}TypeTransformer().encode(value).toString();{{/native_serialization}}
-{{#json_serializable}}    return _${{{classname}}}EnumMap[value];{{/json_serializable}}
+{{#native_serialization}}    return {{{classname}}}TypeTransformer().encode(value).toString();{{/native_serialization}}{{#json_serializable}}    return value.toString();{{/json_serializable}}
   }
       {{/isEnum}}
     {{/model}}
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
index cdf8eb623c9b..7aae686d77b6 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
@@ -31,7 +31,7 @@ class AnotherFakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: modelClient');
     }
 
-    final path = '/another-fake/dummy';
+    final path = r'/another-fake/dummy';
 
     Object postBody = modelClient;
 
@@ -84,8 +84,8 @@ class AnotherFakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
+      return ModelClient.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
index 24fba9d8349e..0a00c3eca905 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
@@ -17,7 +17,7 @@ class DefaultApi {
 
   /// Performs an HTTP 'GET /foo' operation and returns the [Response].
   Future<Response> fooGetWithHttpInfo() async {
-    final path = '/foo';
+    final path = r'/foo';
 
     Object postBody;
 
@@ -62,8 +62,8 @@ class DefaultApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'InlineResponseDefault') as InlineResponseDefault;
+      return InlineResponseDefault.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
index e81da089940d..e3f158d136c5 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
@@ -19,7 +19,7 @@ class FakeApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> fakeHealthGetWithHttpInfo() async {
-    final path = '/fake/health';
+    final path = r'/fake/health';
 
     Object postBody;
 
@@ -65,9 +65,9 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'HealthCheckResult') as HealthCheckResult;
+      return HealthCheckResult.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// test http signature authentication
@@ -90,7 +90,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/fake/http-signature-test';
+    final path = r'/fake/http-signature-test';
 
     Object postBody = pet;
 
@@ -164,7 +164,7 @@ class FakeApi {
   Future<Response> fakeOuterBooleanSerializeWithHttpInfo({ bool body }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/boolean';
+    final path = r'/fake/outer/boolean';
 
     Object postBody = body;
 
@@ -215,9 +215,9 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'bool') as bool;
+      return bool.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Test serialization of object with outer number type
@@ -231,7 +231,7 @@ class FakeApi {
   Future<Response> fakeOuterCompositeSerializeWithHttpInfo({ OuterComposite outerComposite }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/composite';
+    final path = r'/fake/outer/composite';
 
     Object postBody = outerComposite;
 
@@ -282,9 +282,9 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'OuterComposite') as OuterComposite;
+      return OuterComposite.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Test serialization of outer number types
@@ -298,7 +298,7 @@ class FakeApi {
   Future<Response> fakeOuterNumberSerializeWithHttpInfo({ num body }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/number';
+    final path = r'/fake/outer/number';
 
     Object postBody = body;
 
@@ -349,9 +349,9 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'num') as num;
+      return num.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Test serialization of outer string types
@@ -365,7 +365,7 @@ class FakeApi {
   Future<Response> fakeOuterStringSerializeWithHttpInfo({ String body }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/string';
+    final path = r'/fake/outer/string';
 
     Object postBody = body;
 
@@ -416,9 +416,9 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return String.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// For this test, the body for this request much reference a schema named `File`.
@@ -434,7 +434,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: fileSchemaTestClass');
     }
 
-    final path = '/fake/body-with-file-schema';
+    final path = r'/fake/body-with-file-schema';
 
     Object postBody = fileSchemaTestClass;
 
@@ -497,7 +497,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/fake/body-with-query-params';
+    final path = r'/fake/body-with-query-params';
 
     Object postBody = user;
 
@@ -563,7 +563,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: modelClient');
     }
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody = modelClient;
 
@@ -616,9 +616,9 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
+      return ModelClient.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Fake endpoint for testing various parameters 假端點 偽のエンドポイント 가짜 엔드 포인트 
@@ -685,7 +685,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: byte');
     }
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody;
 
@@ -905,7 +905,7 @@ class FakeApi {
   Future<Response> testEnumParametersWithHttpInfo({ List<String> enumHeaderStringArray, String enumHeaderString, List<String> enumQueryStringArray, String enumQueryString, int enumQueryInteger, double enumQueryDouble, List<String> enumFormStringArray, String enumFormString }) async {
     // Verify required params are set.
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody;
 
@@ -1048,7 +1048,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: requiredInt64Group');
     }
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody;
 
@@ -1142,7 +1142,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: requestBody');
     }
 
-    final path = '/fake/inline-additionalProperties';
+    final path = r'/fake/inline-additionalProperties';
 
     Object postBody = requestBody;
 
@@ -1211,7 +1211,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: param2');
     }
 
-    final path = '/fake/jsonFormData';
+    final path = r'/fake/jsonFormData';
 
     Object postBody;
 
@@ -1310,7 +1310,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: context');
     }
 
-    final path = '/fake/test-query-paramters';
+    final path = r'/fake/test-query-paramters';
 
     Object postBody;
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index 66a5c292f0c6..51ed8e1e8828 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -31,7 +31,7 @@ class FakeClassnameTags123Api {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: modelClient');
     }
 
-    final path = '/fake_classname_test';
+    final path = r'/fake_classname_test';
 
     Object postBody = modelClient;
 
@@ -84,8 +84,8 @@ class FakeClassnameTags123Api {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
+      return ModelClient.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
index 71abeecfdd9c..505856c803e8 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
@@ -29,7 +29,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = pet;
 
@@ -94,7 +94,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -166,7 +166,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: status');
     }
 
-    final path = '/pet/findByStatus';
+    final path = r'/pet/findByStatus';
 
     Object postBody;
 
@@ -221,11 +221,10 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
-        .cast<Pet>()
-        .toList(growable: false);
+      final l = json.decode(response.body);
+      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Finds Pets by tags
@@ -244,7 +243,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: tags');
     }
 
-    final path = '/pet/findByTags';
+    final path = r'/pet/findByTags';
 
     Object postBody;
 
@@ -299,11 +298,10 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'Set<Pet>') as List)
-        .cast<Pet>()
-        .toSet();
+      final l = json.decode(response.body);
+      return Set<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Find pet by ID
@@ -322,7 +320,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -376,9 +374,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return Pet.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Update an existing pet
@@ -395,7 +393,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = pet;
 
@@ -464,7 +462,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -554,7 +552,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}/uploadImage'
+    final path = r'/pet/{petId}/uploadImage'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -624,9 +622,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return ApiResponse.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// uploads an image (required)
@@ -652,7 +650,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: requiredFile');
     }
 
-    final path = '/fake/{petId}/uploadImageWithRequiredFile'
+    final path = r'/fake/{petId}/uploadImageWithRequiredFile'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -722,8 +720,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return ApiResponse.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
index bf83f6a25231..289f48d2abe0 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
@@ -31,7 +31,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{order_id}'
+    final path = r'/store/order/{order_id}'
       .replaceAll('{' + 'order_id' + '}', orderId.toString());
 
     Object postBody;
@@ -89,7 +89,7 @@ class StoreApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> getInventoryWithHttpInfo() async {
-    final path = '/store/inventory';
+    final path = r'/store/inventory';
 
     Object postBody;
 
@@ -137,9 +137,9 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return Map<String, int>.from(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Find purchase order by ID
@@ -158,7 +158,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{order_id}'
+    final path = r'/store/order/{order_id}'
       .replaceAll('{' + 'order_id' + '}', orderId.toString());
 
     Object postBody;
@@ -212,9 +212,9 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Place an order for a pet
@@ -231,7 +231,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: order');
     }
 
-    final path = '/store/order';
+    final path = r'/store/order';
 
     Object postBody = order;
 
@@ -282,8 +282,8 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
index 76d477efeb36..e1981eeb471c 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
@@ -31,7 +31,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user';
+    final path = r'/user';
 
     Object postBody = user;
 
@@ -96,7 +96,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/createWithArray';
+    final path = r'/user/createWithArray';
 
     Object postBody = user;
 
@@ -159,7 +159,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/createWithList';
+    final path = r'/user/createWithList';
 
     Object postBody = user;
 
@@ -224,7 +224,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -290,7 +290,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -342,9 +342,9 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return User.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Logs user into the system
@@ -367,7 +367,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: password');
     }
 
-    final path = '/user/login';
+    final path = r'/user/login';
 
     Object postBody;
 
@@ -424,16 +424,16 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return String.fromJson(json.decode(response.body));
     }
-    return null;
+    return Future.value(null);
   }
 
   /// Logs out current logged in user session
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> logoutUserWithHttpInfo() async {
-    final path = '/user/logout';
+    final path = r'/user/logout';
 
     Object postBody;
 
@@ -499,7 +499,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody = user;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_client.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_client.dart
index 435fdfc4b74a..593d552210b5 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_client.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_client.dart
@@ -52,17 +52,6 @@ class ApiClient {
   Map<String, Authentication> get authentications =>
       Map.unmodifiable(_authentications);
 
-  dynamic deserialize(String json, String targetType, {bool growable}) {
-    // Remove all spaces.  Necessary for reg expressions as well.
-    targetType = targetType.replaceAll(' ', '');
-
-    return targetType == 'String'
-      ? json
-      : _deserialize(jsonDecode(json), targetType, growable: true == growable);
-  }
-
-  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
-
   T getAuthentication<T extends Authentication>(String name) {
     final authentication = _authentications[name];
     return authentication is T ? authentication : null;
@@ -155,141 +144,8 @@ class ApiClient {
     throw ApiException(HttpStatus.badRequest, 'Invalid HTTP operation: $method $path',);
   }
 
-  dynamic _deserialize(dynamic value, String targetType, {bool growable}) {
-    try {
-      switch (targetType) {
-        case 'String':
-          return '$value';
-        case 'int':
-          return value is int ? value : int.parse('$value');
-        case 'bool':
-          if (value is bool) {
-            return value;
-          }
-          final valueString = '$value'.toLowerCase();
-          return valueString == 'true' || valueString == '1';
-          break;
-        case 'double':
-          return value is double ? value : double.parse('$value');
-        case 'AdditionalPropertiesClass':
-          return AdditionalPropertiesClass.fromJson(value);
-        case 'Animal':
-          return Animal.fromJson(value);
-        case 'ApiResponse':
-          return ApiResponse.fromJson(value);
-        case 'ArrayOfArrayOfNumberOnly':
-          return ArrayOfArrayOfNumberOnly.fromJson(value);
-        case 'ArrayOfNumberOnly':
-          return ArrayOfNumberOnly.fromJson(value);
-        case 'ArrayTest':
-          return ArrayTest.fromJson(value);
-        case 'Capitalization':
-          return Capitalization.fromJson(value);
-        case 'Cat':
-          return Cat.fromJson(value);
-        case 'CatAllOf':
-          return CatAllOf.fromJson(value);
-        case 'Category':
-          return Category.fromJson(value);
-        case 'ClassModel':
-          return ClassModel.fromJson(value);
-        case 'Dog':
-          return Dog.fromJson(value);
-        case 'DogAllOf':
-          return DogAllOf.fromJson(value);
-        case 'EnumArrays':
-          return EnumArrays.fromJson(value);
-        case 'EnumClass':
-          
-           return _$enumDecode(_$EnumClassEnumMap, value);
-        case 'EnumTest':
-          return EnumTest.fromJson(value);
-        case 'FileSchemaTestClass':
-          return FileSchemaTestClass.fromJson(value);
-        case 'Foo':
-          return Foo.fromJson(value);
-        case 'FormatTest':
-          return FormatTest.fromJson(value);
-        case 'HasOnlyReadOnly':
-          return HasOnlyReadOnly.fromJson(value);
-        case 'HealthCheckResult':
-          return HealthCheckResult.fromJson(value);
-        case 'InlineResponseDefault':
-          return InlineResponseDefault.fromJson(value);
-        case 'MapTest':
-          return MapTest.fromJson(value);
-        case 'MixedPropertiesAndAdditionalPropertiesClass':
-          return MixedPropertiesAndAdditionalPropertiesClass.fromJson(value);
-        case 'Model200Response':
-          return Model200Response.fromJson(value);
-        case 'ModelClient':
-          return ModelClient.fromJson(value);
-        case 'ModelFile':
-          return ModelFile.fromJson(value);
-        case 'ModelList':
-          return ModelList.fromJson(value);
-        case 'ModelReturn':
-          return ModelReturn.fromJson(value);
-        case 'Name':
-          return Name.fromJson(value);
-        case 'NullableClass':
-          return NullableClass.fromJson(value);
-        case 'NumberOnly':
-          return NumberOnly.fromJson(value);
-        case 'Order':
-          return Order.fromJson(value);
-        case 'OuterComposite':
-          return OuterComposite.fromJson(value);
-        case 'OuterEnum':
-          
-           return _$enumDecode(_$OuterEnumEnumMap, value);
-        case 'OuterEnumDefaultValue':
-          
-           return _$enumDecode(_$OuterEnumDefaultValueEnumMap, value);
-        case 'OuterEnumInteger':
-          
-           return _$enumDecode(_$OuterEnumIntegerEnumMap, value);
-        case 'OuterEnumIntegerDefaultValue':
-          
-           return _$enumDecode(_$OuterEnumIntegerDefaultValueEnumMap, value);
-        case 'Pet':
-          return Pet.fromJson(value);
-        case 'ReadOnlyFirst':
-          return ReadOnlyFirst.fromJson(value);
-        case 'SpecialModelName':
-          return SpecialModelName.fromJson(value);
-        case 'Tag':
-          return Tag.fromJson(value);
-        case 'User':
-          return User.fromJson(value);
-        default:
-          Match match;
-          if (value is List && (match = _regList.firstMatch(targetType)) != null) {
-            final newTargetType = match[1];
-            return value
-              .map((v) => _deserialize(v, newTargetType, growable: growable))
-              .toList(growable: true == growable);
-          }
-          if (value is Set && (match = _regSet.firstMatch(targetType)) != null) {
-            final newTargetType = match[1];
-            return value
-              .map((v) => _deserialize(v, newTargetType, growable: growable))
-              .toSet();
-          }
-          if (value is Map && (match = _regMap.firstMatch(targetType)) != null) {
-            final newTargetType = match[1];
-            return Map.fromIterables(
-              value.keys,
-              value.values.map((v) => _deserialize(v, newTargetType, growable: growable)),
-            );
-          }
-          break;
-      }
-    } on Exception catch (e, stack) {
-      throw ApiException.withInner(HttpStatus.internalServerError, 'Exception during deserialization.', e, stack,);
-    }
-    throw ApiException(HttpStatus.internalServerError, 'Could not find a suitable class for deserialization',);
-  }
+
+  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
 
   /// Update query and header parameters based on authentication settings.
   /// @param authNames The authentications to apply
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_helper.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_helper.dart
index 8e083e63f0a4..f9904f5ec71e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_helper.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api_helper.dart
@@ -59,24 +59,19 @@ String parameterToString(dynamic value) {
     return value.toUtc().toIso8601String();
   }
   if (value is EnumClass) {
-
-    return _$EnumClassEnumMap[value];
+    return value.toString();
   }
   if (value is OuterEnum) {
-
-    return _$OuterEnumEnumMap[value];
+    return value.toString();
   }
   if (value is OuterEnumDefaultValue) {
-
-    return _$OuterEnumDefaultValueEnumMap[value];
+    return value.toString();
   }
   if (value is OuterEnumInteger) {
-
-    return _$OuterEnumIntegerEnumMap[value];
+    return value.toString();
   }
   if (value is OuterEnumIntegerDefaultValue) {
-
-    return _$OuterEnumIntegerDefaultValueEnumMap[value];
+    return value.toString();
   }
   return value.toString();
 }

From 7073f54be57d6b6b19f3935ab9fcc8e6f479c624 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Wed, 3 Mar 2021 20:27:08 +0000
Subject: [PATCH 2/9] Use raw string for url path

---
 .../src/main/resources/dart2/api.mustache     |  5 +--
 .../petstore_client_lib/lib/api/pet_api.dart  | 30 +++++++------
 .../lib/api/store_api.dart                    | 14 +++----
 .../petstore_client_lib/lib/api/user_api.dart | 20 ++++-----
 .../petstore_client_lib/lib/api_client.dart   | 22 +++++-----
 .../petstore_client_lib/lib/api/pet_api.dart  | 34 +++++++--------
 .../lib/api/store_api.dart                    | 14 +++----
 .../petstore_client_lib/lib/api/user_api.dart | 20 ++++-----
 .../petstore_client_lib/lib/api_client.dart   | 22 +++++-----
 .../lib/api/another_fake_api.dart             |  4 +-
 .../lib/api/default_api.dart                  |  4 +-
 .../lib/api/fake_api.dart                     | 42 +++++++++----------
 .../lib/api/fake_classname_tags123_api.dart   |  4 +-
 .../lib/api/pet_api.dart                      | 34 +++++++--------
 .../lib/api/store_api.dart                    | 14 +++----
 .../lib/api/user_api.dart                     | 20 ++++-----
 .../lib/api_client.dart                       | 22 +++++-----
 .../lib/api_helper.dart                       |  5 ---
 .../lib/api/another_fake_api.dart             |  2 +-
 .../lib/api/default_api.dart                  |  2 +-
 .../lib/api/fake_api.dart                     | 12 +++---
 .../lib/api/fake_classname_tags123_api.dart   |  2 +-
 .../lib/api/pet_api.dart                      | 10 ++---
 .../lib/api/store_api.dart                    |  6 +--
 .../lib/api/user_api.dart                     |  4 +-
 25 files changed, 177 insertions(+), 191 deletions(-)

diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index af852b117566..4b126db8500b 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -197,11 +197,8 @@ class {{{classname}}} {
       return {{{returnType}}}.fromJson(json.decode(response.body));
     {{/isMap}}
     {{/isArray}}
-    {{#isString}}
-      return json.decode(response.body);
-    {{/isString}}
     }
-    return Future.value(null);
+    return null;
     {{/returnType}}
   }
   {{/operation}}
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index df7ee07412ed..d6b86a23b3ef 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -29,7 +29,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = body;
 
@@ -94,7 +94,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -166,7 +166,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: status');
     }
 
-    final path = '/pet/findByStatus';
+    final path = r'/pet/findByStatus';
 
     Object postBody;
 
@@ -221,9 +221,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
-        .cast<Pet>()
-        .toList(growable: false);
+      final l = json.decode(response.body);
+      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -244,7 +243,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: tags');
     }
 
-    final path = '/pet/findByTags';
+    final path = r'/pet/findByTags';
 
     Object postBody;
 
@@ -299,9 +298,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
-        .cast<Pet>()
-        .toList(growable: false);
+      final l = json.decode(response.body);
+      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -322,7 +320,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -376,7 +374,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return Pet.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -395,7 +393,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = body;
 
@@ -464,7 +462,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -554,7 +552,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}/uploadImage'
+    final path = r'/pet/{petId}/uploadImage'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -624,7 +622,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return ApiResponse.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
index 1f20bf42f74b..80a1d0ff30ce 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
@@ -31,7 +31,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{orderId}'
+    final path = r'/store/order/{orderId}'
       .replaceAll('{' + 'orderId' + '}', orderId.toString());
 
     Object postBody;
@@ -89,7 +89,7 @@ class StoreApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> getInventoryWithHttpInfo() async {
-    final path = '/store/inventory';
+    final path = r'/store/inventory';
 
     Object postBody;
 
@@ -137,7 +137,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return Map<String, int>.from(json.decode(response.body));
     }
     return null;
   }
@@ -158,7 +158,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{orderId}'
+    final path = r'/store/order/{orderId}'
       .replaceAll('{' + 'orderId' + '}', orderId.toString());
 
     Object postBody;
@@ -212,7 +212,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -231,7 +231,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/store/order';
+    final path = r'/store/order';
 
     Object postBody = body;
 
@@ -282,7 +282,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index a8a566239ca7..d3b3e7106469 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -31,7 +31,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/user';
+    final path = r'/user';
 
     Object postBody = body;
 
@@ -96,7 +96,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/user/createWithArray';
+    final path = r'/user/createWithArray';
 
     Object postBody = body;
 
@@ -159,7 +159,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/user/createWithList';
+    final path = r'/user/createWithList';
 
     Object postBody = body;
 
@@ -224,7 +224,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -290,7 +290,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -342,7 +342,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return User.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -367,7 +367,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: password');
     }
 
-    final path = '/user/login';
+    final path = r'/user/login';
 
     Object postBody;
 
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return String.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -433,7 +433,7 @@ class UserApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> logoutUserWithHttpInfo() async {
-    final path = '/user/logout';
+    final path = r'/user/logout';
 
     Object postBody;
 
@@ -499,7 +499,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: body');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody = body;
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api_client.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
index 9f875dba12d6..87a7a36d470b 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
@@ -49,17 +49,6 @@ class ApiClient {
   Map<String, Authentication> get authentications =>
       Map.unmodifiable(_authentications);
 
-  dynamic deserialize(String json, String targetType, {bool growable}) {
-    // Remove all spaces.  Necessary for reg expressions as well.
-    targetType = targetType.replaceAll(' ', '');
-
-    return targetType == 'String'
-      ? json
-      : _deserialize(jsonDecode(json), targetType, growable: true == growable);
-  }
-
-  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
-
   T getAuthentication<T extends Authentication>(String name) {
     final authentication = _authentications[name];
     return authentication is T ? authentication : null;
@@ -209,6 +198,17 @@ class ApiClient {
     throw ApiException(HttpStatus.internalServerError, 'Could not find a suitable class for deserialization',);
   }
 
+  dynamic deserialize(String json, String targetType, {bool growable}) {
+    // Remove all spaces.  Necessary for reg expressions as well.
+    targetType = targetType.replaceAll(' ', '');
+
+  return targetType == 'String'
+    ? json
+    : _deserialize(jsonDecode(json), targetType, growable: true == growable);
+  }
+
+  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
+
   /// Update query and header parameters based on authentication settings.
   /// @param authNames The authentications to apply
   void _updateParamsForAuth(
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index f0d8178af255..22e121c8ce21 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -29,7 +29,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = pet;
 
@@ -80,7 +80,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return Pet.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -101,7 +101,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -173,7 +173,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: status');
     }
 
-    final path = '/pet/findByStatus';
+    final path = r'/pet/findByStatus';
 
     Object postBody;
 
@@ -228,9 +228,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
-        .cast<Pet>()
-        .toList(growable: false);
+      final l = json.decode(response.body);
+      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -251,7 +250,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: tags');
     }
 
-    final path = '/pet/findByTags';
+    final path = r'/pet/findByTags';
 
     Object postBody;
 
@@ -306,9 +305,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
-        .cast<Pet>()
-        .toList(growable: false);
+      final l = json.decode(response.body);
+      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -329,7 +327,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -383,7 +381,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return Pet.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -402,7 +400,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = pet;
 
@@ -453,7 +451,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return Pet.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -478,7 +476,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -568,7 +566,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}/uploadImage'
+    final path = r'/pet/{petId}/uploadImage'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -638,7 +636,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return ApiResponse.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
index 121395c60f04..65417433adad 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
@@ -31,7 +31,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{orderId}'
+    final path = r'/store/order/{orderId}'
       .replaceAll('{' + 'orderId' + '}', orderId.toString());
 
     Object postBody;
@@ -89,7 +89,7 @@ class StoreApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> getInventoryWithHttpInfo() async {
-    final path = '/store/inventory';
+    final path = r'/store/inventory';
 
     Object postBody;
 
@@ -137,7 +137,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return Map<String, int>.from(json.decode(response.body));
     }
     return null;
   }
@@ -158,7 +158,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{orderId}'
+    final path = r'/store/order/{orderId}'
       .replaceAll('{' + 'orderId' + '}', orderId.toString());
 
     Object postBody;
@@ -212,7 +212,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -231,7 +231,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: order');
     }
 
-    final path = '/store/order';
+    final path = r'/store/order';
 
     Object postBody = order;
 
@@ -282,7 +282,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index 156dcc272a50..dcba5233f75b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -31,7 +31,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user';
+    final path = r'/user';
 
     Object postBody = user;
 
@@ -96,7 +96,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/createWithArray';
+    final path = r'/user/createWithArray';
 
     Object postBody = user;
 
@@ -159,7 +159,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/createWithList';
+    final path = r'/user/createWithList';
 
     Object postBody = user;
 
@@ -224,7 +224,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -290,7 +290,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -342,7 +342,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return User.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -367,7 +367,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: password');
     }
 
-    final path = '/user/login';
+    final path = r'/user/login';
 
     Object postBody;
 
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return String.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -433,7 +433,7 @@ class UserApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> logoutUserWithHttpInfo() async {
-    final path = '/user/logout';
+    final path = r'/user/logout';
 
     Object postBody;
 
@@ -499,7 +499,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody = user;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
index 9f875dba12d6..87a7a36d470b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
@@ -49,17 +49,6 @@ class ApiClient {
   Map<String, Authentication> get authentications =>
       Map.unmodifiable(_authentications);
 
-  dynamic deserialize(String json, String targetType, {bool growable}) {
-    // Remove all spaces.  Necessary for reg expressions as well.
-    targetType = targetType.replaceAll(' ', '');
-
-    return targetType == 'String'
-      ? json
-      : _deserialize(jsonDecode(json), targetType, growable: true == growable);
-  }
-
-  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
-
   T getAuthentication<T extends Authentication>(String name) {
     final authentication = _authentications[name];
     return authentication is T ? authentication : null;
@@ -209,6 +198,17 @@ class ApiClient {
     throw ApiException(HttpStatus.internalServerError, 'Could not find a suitable class for deserialization',);
   }
 
+  dynamic deserialize(String json, String targetType, {bool growable}) {
+    // Remove all spaces.  Necessary for reg expressions as well.
+    targetType = targetType.replaceAll(' ', '');
+
+  return targetType == 'String'
+    ? json
+    : _deserialize(jsonDecode(json), targetType, growable: true == growable);
+  }
+
+  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
+
   /// Update query and header parameters based on authentication settings.
   /// @param authNames The authentications to apply
   void _updateParamsForAuth(
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
index cdf8eb623c9b..9d2741900e2a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
@@ -31,7 +31,7 @@ class AnotherFakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: modelClient');
     }
 
-    final path = '/another-fake/dummy';
+    final path = r'/another-fake/dummy';
 
     Object postBody = modelClient;
 
@@ -84,7 +84,7 @@ class AnotherFakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
+      return ModelClient.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
index 24fba9d8349e..bfb3f296cc5b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
@@ -17,7 +17,7 @@ class DefaultApi {
 
   /// Performs an HTTP 'GET /foo' operation and returns the [Response].
   Future<Response> fooGetWithHttpInfo() async {
-    final path = '/foo';
+    final path = r'/foo';
 
     Object postBody;
 
@@ -62,7 +62,7 @@ class DefaultApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'InlineResponseDefault') as InlineResponseDefault;
+      return InlineResponseDefault.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
index e81da089940d..f483395b4d7d 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -19,7 +19,7 @@ class FakeApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> fakeHealthGetWithHttpInfo() async {
-    final path = '/fake/health';
+    final path = r'/fake/health';
 
     Object postBody;
 
@@ -65,7 +65,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'HealthCheckResult') as HealthCheckResult;
+      return HealthCheckResult.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -90,7 +90,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/fake/http-signature-test';
+    final path = r'/fake/http-signature-test';
 
     Object postBody = pet;
 
@@ -164,7 +164,7 @@ class FakeApi {
   Future<Response> fakeOuterBooleanSerializeWithHttpInfo({ bool body }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/boolean';
+    final path = r'/fake/outer/boolean';
 
     Object postBody = body;
 
@@ -215,7 +215,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'bool') as bool;
+      return bool.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -231,7 +231,7 @@ class FakeApi {
   Future<Response> fakeOuterCompositeSerializeWithHttpInfo({ OuterComposite outerComposite }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/composite';
+    final path = r'/fake/outer/composite';
 
     Object postBody = outerComposite;
 
@@ -282,7 +282,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'OuterComposite') as OuterComposite;
+      return OuterComposite.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -298,7 +298,7 @@ class FakeApi {
   Future<Response> fakeOuterNumberSerializeWithHttpInfo({ num body }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/number';
+    final path = r'/fake/outer/number';
 
     Object postBody = body;
 
@@ -349,7 +349,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'num') as num;
+      return num.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -365,7 +365,7 @@ class FakeApi {
   Future<Response> fakeOuterStringSerializeWithHttpInfo({ String body }) async {
     // Verify required params are set.
 
-    final path = '/fake/outer/string';
+    final path = r'/fake/outer/string';
 
     Object postBody = body;
 
@@ -416,7 +416,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return String.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -434,7 +434,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: fileSchemaTestClass');
     }
 
-    final path = '/fake/body-with-file-schema';
+    final path = r'/fake/body-with-file-schema';
 
     Object postBody = fileSchemaTestClass;
 
@@ -497,7 +497,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/fake/body-with-query-params';
+    final path = r'/fake/body-with-query-params';
 
     Object postBody = user;
 
@@ -563,7 +563,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: modelClient');
     }
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody = modelClient;
 
@@ -616,7 +616,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
+      return ModelClient.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -685,7 +685,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: byte');
     }
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody;
 
@@ -905,7 +905,7 @@ class FakeApi {
   Future<Response> testEnumParametersWithHttpInfo({ List<String> enumHeaderStringArray, String enumHeaderString, List<String> enumQueryStringArray, String enumQueryString, int enumQueryInteger, double enumQueryDouble, List<String> enumFormStringArray, String enumFormString }) async {
     // Verify required params are set.
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody;
 
@@ -1048,7 +1048,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: requiredInt64Group');
     }
 
-    final path = '/fake';
+    final path = r'/fake';
 
     Object postBody;
 
@@ -1142,7 +1142,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: requestBody');
     }
 
-    final path = '/fake/inline-additionalProperties';
+    final path = r'/fake/inline-additionalProperties';
 
     Object postBody = requestBody;
 
@@ -1211,7 +1211,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: param2');
     }
 
-    final path = '/fake/jsonFormData';
+    final path = r'/fake/jsonFormData';
 
     Object postBody;
 
@@ -1310,7 +1310,7 @@ class FakeApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: context');
     }
 
-    final path = '/fake/test-query-paramters';
+    final path = r'/fake/test-query-paramters';
 
     Object postBody;
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index 66a5c292f0c6..b3fb785d9ad0 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -31,7 +31,7 @@ class FakeClassnameTags123Api {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: modelClient');
     }
 
-    final path = '/fake_classname_test';
+    final path = r'/fake_classname_test';
 
     Object postBody = modelClient;
 
@@ -84,7 +84,7 @@ class FakeClassnameTags123Api {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
+      return ModelClient.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
index 71abeecfdd9c..5f7324df77b2 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
@@ -29,7 +29,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = pet;
 
@@ -94,7 +94,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -166,7 +166,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: status');
     }
 
-    final path = '/pet/findByStatus';
+    final path = r'/pet/findByStatus';
 
     Object postBody;
 
@@ -221,9 +221,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'List<Pet>') as List)
-        .cast<Pet>()
-        .toList(growable: false);
+      final l = json.decode(response.body);
+      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -244,7 +243,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: tags');
     }
 
-    final path = '/pet/findByTags';
+    final path = r'/pet/findByTags';
 
     Object postBody;
 
@@ -299,9 +298,8 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return (apiClient.deserialize(_decodeBodyBytes(response), 'Set<Pet>') as List)
-        .cast<Pet>()
-        .toSet();
+      final l = json.decode(response.body);
+      return Set<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -322,7 +320,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -376,7 +374,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
+      return Pet.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -395,7 +393,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: pet');
     }
 
-    final path = '/pet';
+    final path = r'/pet';
 
     Object postBody = pet;
 
@@ -464,7 +462,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}'
+    final path = r'/pet/{petId}'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -554,7 +552,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: petId');
     }
 
-    final path = '/pet/{petId}/uploadImage'
+    final path = r'/pet/{petId}/uploadImage'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -624,7 +622,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return ApiResponse.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -652,7 +650,7 @@ class PetApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: requiredFile');
     }
 
-    final path = '/fake/{petId}/uploadImageWithRequiredFile'
+    final path = r'/fake/{petId}/uploadImageWithRequiredFile'
       .replaceAll('{' + 'petId' + '}', petId.toString());
 
     Object postBody;
@@ -722,7 +720,7 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
+      return ApiResponse.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
index bf83f6a25231..ef9006cd512e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
@@ -31,7 +31,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{order_id}'
+    final path = r'/store/order/{order_id}'
       .replaceAll('{' + 'order_id' + '}', orderId.toString());
 
     Object postBody;
@@ -89,7 +89,7 @@ class StoreApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> getInventoryWithHttpInfo() async {
-    final path = '/store/inventory';
+    final path = r'/store/inventory';
 
     Object postBody;
 
@@ -137,7 +137,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
+      return Map<String, int>.from(json.decode(response.body));
     }
     return null;
   }
@@ -158,7 +158,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: orderId');
     }
 
-    final path = '/store/order/{order_id}'
+    final path = r'/store/order/{order_id}'
       .replaceAll('{' + 'order_id' + '}', orderId.toString());
 
     Object postBody;
@@ -212,7 +212,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -231,7 +231,7 @@ class StoreApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: order');
     }
 
-    final path = '/store/order';
+    final path = r'/store/order';
 
     Object postBody = order;
 
@@ -282,7 +282,7 @@ class StoreApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
+      return Order.fromJson(json.decode(response.body));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
index 76d477efeb36..ba0ddb7ea863 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
@@ -31,7 +31,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user';
+    final path = r'/user';
 
     Object postBody = user;
 
@@ -96,7 +96,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/createWithArray';
+    final path = r'/user/createWithArray';
 
     Object postBody = user;
 
@@ -159,7 +159,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/createWithList';
+    final path = r'/user/createWithList';
 
     Object postBody = user;
 
@@ -224,7 +224,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -290,7 +290,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: username');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody;
@@ -342,7 +342,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
+      return User.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -367,7 +367,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: password');
     }
 
-    final path = '/user/login';
+    final path = r'/user/login';
 
     Object postBody;
 
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
+      return String.fromJson(json.decode(response.body));
     }
     return null;
   }
@@ -433,7 +433,7 @@ class UserApi {
   ///
   /// Note: This method returns the HTTP [Response].
   Future<Response> logoutUserWithHttpInfo() async {
-    final path = '/user/logout';
+    final path = r'/user/logout';
 
     Object postBody;
 
@@ -499,7 +499,7 @@ class UserApi {
      throw ApiException(HttpStatus.badRequest, 'Missing required param: user');
     }
 
-    final path = '/user/{username}'
+    final path = r'/user/{username}'
       .replaceAll('{' + 'username' + '}', username.toString());
 
     Object postBody = user;
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart
index 864e189b21a4..ac9f67d242d4 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart
@@ -52,17 +52,6 @@ class ApiClient {
   Map<String, Authentication> get authentications =>
       Map.unmodifiable(_authentications);
 
-  dynamic deserialize(String json, String targetType, {bool growable}) {
-    // Remove all spaces.  Necessary for reg expressions as well.
-    targetType = targetType.replaceAll(' ', '');
-
-    return targetType == 'String'
-      ? json
-      : _deserialize(jsonDecode(json), targetType, growable: true == growable);
-  }
-
-  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
-
   T getAuthentication<T extends Authentication>(String name) {
     final authentication = _authentications[name];
     return authentication is T ? authentication : null;
@@ -291,6 +280,17 @@ class ApiClient {
     throw ApiException(HttpStatus.internalServerError, 'Could not find a suitable class for deserialization',);
   }
 
+  dynamic deserialize(String json, String targetType, {bool growable}) {
+    // Remove all spaces.  Necessary for reg expressions as well.
+    targetType = targetType.replaceAll(' ', '');
+
+  return targetType == 'String'
+    ? json
+    : _deserialize(jsonDecode(json), targetType, growable: true == growable);
+  }
+
+  String serialize(Object obj) => obj == null ? '' : json.encode(obj);
+
   /// Update query and header parameters based on authentication settings.
   /// @param authNames The authentications to apply
   void _updateParamsForAuth(
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_helper.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_helper.dart
index d307b920991d..ececff49c4c8 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_helper.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_helper.dart
@@ -60,23 +60,18 @@ String parameterToString(dynamic value) {
   }
   if (value is EnumClass) {
     return EnumClassTypeTransformer().encode(value).toString();
-
   }
   if (value is OuterEnum) {
     return OuterEnumTypeTransformer().encode(value).toString();
-
   }
   if (value is OuterEnumDefaultValue) {
     return OuterEnumDefaultValueTypeTransformer().encode(value).toString();
-
   }
   if (value is OuterEnumInteger) {
     return OuterEnumIntegerTypeTransformer().encode(value).toString();
-
   }
   if (value is OuterEnumIntegerDefaultValue) {
     return OuterEnumIntegerDefaultValueTypeTransformer().encode(value).toString();
-
   }
   return value.toString();
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
index 7aae686d77b6..9d2741900e2a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
@@ -86,6 +86,6 @@ class AnotherFakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return ModelClient.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
index 0a00c3eca905..bfb3f296cc5b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
@@ -64,6 +64,6 @@ class DefaultApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return InlineResponseDefault.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
index e3f158d136c5..f483395b4d7d 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
@@ -67,7 +67,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return HealthCheckResult.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// test http signature authentication
@@ -217,7 +217,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return bool.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Test serialization of object with outer number type
@@ -284,7 +284,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return OuterComposite.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Test serialization of outer number types
@@ -351,7 +351,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return num.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Test serialization of outer string types
@@ -418,7 +418,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return String.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// For this test, the body for this request much reference a schema named `File`.
@@ -618,7 +618,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return ModelClient.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Fake endpoint for testing various parameters 假端點 偽のエンドポイント 가짜 엔드 포인트 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index 51ed8e1e8828..b3fb785d9ad0 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -86,6 +86,6 @@ class FakeClassnameTags123Api {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return ModelClient.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
index 505856c803e8..5f7324df77b2 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
@@ -224,7 +224,7 @@ class PetApi {
       final l = json.decode(response.body);
       return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Finds Pets by tags
@@ -301,7 +301,7 @@ class PetApi {
       final l = json.decode(response.body);
       return Set<Pet>.from(l.map((model) => Pet.fromJson(model)));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Find pet by ID
@@ -376,7 +376,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Pet.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Update an existing pet
@@ -624,7 +624,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return ApiResponse.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// uploads an image (required)
@@ -722,6 +722,6 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return ApiResponse.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
index 289f48d2abe0..ef9006cd512e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
@@ -139,7 +139,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Map<String, int>.from(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Find purchase order by ID
@@ -214,7 +214,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Order.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Place an order for a pet
@@ -284,6 +284,6 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Order.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
index e1981eeb471c..ba0ddb7ea863 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
@@ -344,7 +344,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return User.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Logs user into the system
@@ -426,7 +426,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return String.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return null;
   }
 
   /// Logs out current logged in user session

From 8ebe1e23758ce6195121676f2ee3b9e075806ba9 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Wed, 3 Mar 2021 22:02:41 +0000
Subject: [PATCH 3/9] Use Set/List.of

---
 .../src/main/resources/dart2/api.mustache                  | 7 ++++++-
 .../lib/api/pet_api.dart                                   | 4 ++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index 4b126db8500b..81a4672808c6 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -187,14 +187,19 @@ class {{{classname}}} {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
     {{#isArray}}
       final l = json.decode(response.body);
-      return {{{returnType}}}.from(l.map((model) => Pet.fromJson(model)));
+      return {{{returnType}}}.of(l.map((model) => Pet.fromJson(model)));
     {{/isArray}}
     {{^isArray}}
     {{#isMap}}
       return {{{returnType}}}.from(json.decode(response.body));
     {{/isMap}}
     {{^isMap}}
+    {{#isPrimitiveType}}
+      return json.decode(response.body);
+    {{/isPrimitiveType}}
+    {{^isPrimitiveType}}
       return {{{returnType}}}.fromJson(json.decode(response.body));
+    {{/isPrimitiveType}}
     {{/isMap}}
     {{/isArray}}
     }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
index 5f7324df77b2..9f70d83f7eb0 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
@@ -222,7 +222,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -299,7 +299,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return Set<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return Set<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }

From d8af6e15b1d09e5e977e0a72889fe4b94d8d7b96 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Thu, 4 Mar 2021 16:07:53 +0000
Subject: [PATCH 4/9] Use returnTypeIsPrimitive in template

---
 .../src/main/resources/dart2/api.mustache                 | 8 ++++----
 .../lib/api/fake_api.dart                                 | 6 +++---
 .../lib/api/user_api.dart                                 | 2 +-
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index 81a4672808c6..c3f4e3cca6bf 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -194,12 +194,12 @@ class {{{classname}}} {
       return {{{returnType}}}.from(json.decode(response.body));
     {{/isMap}}
     {{^isMap}}
-    {{#isPrimitiveType}}
+    {{#returnTypeIsPrimitive}}
       return json.decode(response.body);
-    {{/isPrimitiveType}}
-    {{^isPrimitiveType}}
+    {{/returnTypeIsPrimitive}}
+    {{^returnTypeIsPrimitive}}
       return {{{returnType}}}.fromJson(json.decode(response.body));
-    {{/isPrimitiveType}}
+    {{/returnTypeIsPrimitive}}
     {{/isMap}}
     {{/isArray}}
     }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
index f483395b4d7d..c37a8bb39479 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
@@ -215,7 +215,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return bool.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
@@ -349,7 +349,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return num.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
@@ -416,7 +416,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return String.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
index ba0ddb7ea863..8075bfea1e5a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return String.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }

From bb55502be20b0586f3609cfee5dd14d0b888ff80 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Thu, 4 Mar 2021 19:44:07 +0000
Subject: [PATCH 5/9] Regenerate all templates

---
 .../petstore/dart2/petstore_client_lib/lib/api/pet_api.dart | 4 ++--
 .../dart2/petstore_client_lib/lib/api/user_api.dart         | 2 +-
 .../petstore/dart2/petstore_client_lib/lib/api/pet_api.dart | 4 ++--
 .../dart2/petstore_client_lib/lib/api/user_api.dart         | 2 +-
 .../dart2/petstore_client_lib_fake/lib/api/fake_api.dart    | 6 +++---
 .../dart2/petstore_client_lib_fake/lib/api/pet_api.dart     | 4 ++--
 .../dart2/petstore_client_lib_fake/lib/api/user_api.dart    | 2 +-
 7 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index d6b86a23b3ef..395d1deea44f 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -222,7 +222,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -299,7 +299,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index d3b3e7106469..8a4a512d5822 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return String.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index 22e121c8ce21..42723a64b435 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -229,7 +229,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -306,7 +306,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index dcba5233f75b..5dd4ccdeb16a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return String.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
index f483395b4d7d..c37a8bb39479 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -215,7 +215,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return bool.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
@@ -349,7 +349,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return num.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
@@ -416,7 +416,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return String.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
index 5f7324df77b2..9f70d83f7eb0 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
@@ -222,7 +222,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return List<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
@@ -299,7 +299,7 @@ class PetApi {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       final l = json.decode(response.body);
-      return Set<Pet>.from(l.map((model) => Pet.fromJson(model)));
+      return Set<Pet>.of(l.map((model) => Pet.fromJson(model)));
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
index ba0ddb7ea863..8075bfea1e5a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return String.fromJson(json.decode(response.body));
+      return json.decode(response.body);
     }
     return null;
   }

From e9c760444ce78499f858f20a497c95f9ab7de324 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Thu, 4 Mar 2021 21:00:40 +0000
Subject: [PATCH 6/9] Fix casting map to Iterable of things

---
 .../src/main/resources/dart2/api.mustache          | 14 +++++++++++---
 .../dart2/petstore_client_lib/lib/api/pet_api.dart | 10 ++++++----
 .../petstore_client_lib/lib/api/user_api.dart      |  2 +-
 .../dart2/petstore_client_lib/lib/api/pet_api.dart | 10 ++++++----
 .../petstore_client_lib/lib/api/user_api.dart      |  2 +-
 .../petstore_client_lib_fake/lib/api/fake_api.dart |  6 +++---
 .../petstore_client_lib_fake/lib/api/pet_api.dart  | 10 ++++++----
 .../petstore_client_lib_fake/lib/api/user_api.dart |  2 +-
 .../lib/api/fake_api.dart                          |  6 +++---
 .../lib/api/pet_api.dart                           | 10 ++++++----
 .../lib/api/user_api.dart                          |  2 +-
 11 files changed, 45 insertions(+), 29 deletions(-)

diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index c3f4e3cca6bf..d198c88b706d 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -186,8 +186,16 @@ class {{{classname}}} {
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
     {{#isArray}}
-      final l = json.decode(response.body);
-      return {{{returnType}}}.of(l.map((model) => Pet.fromJson(model)));
+      {{#uniqueItems}}
+      return (json.decode(response.body) as List)
+        .map((i) => {{{returnBaseType}}}.fromJson(i))
+        .toSet();
+      {{/uniqueItems}}
+      {{^uniqueItems}}
+      return (json.decode(response.body) as List)
+        .map((i) => {{{returnBaseType}}}.fromJson(i))
+        .toList();
+      {{/uniqueItems}}
     {{/isArray}}
     {{^isArray}}
     {{#isMap}}
@@ -195,7 +203,7 @@ class {{{classname}}} {
     {{/isMap}}
     {{^isMap}}
     {{#returnTypeIsPrimitive}}
-      return json.decode(response.body);
+      return response.body as {{{returnBaseType}}};
     {{/returnTypeIsPrimitive}}
     {{^returnTypeIsPrimitive}}
       return {{{returnType}}}.fromJson(json.decode(response.body));
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index 395d1deea44f..cab952fe0d1a 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -221,8 +221,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toList();
     }
     return null;
   }
@@ -298,8 +299,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toList();
     }
     return null;
   }
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index 8a4a512d5822..4569e3ddfc38 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as String;
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index 42723a64b435..c441744ac661 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -228,8 +228,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toList();
     }
     return null;
   }
@@ -305,8 +306,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toList();
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index 5dd4ccdeb16a..8ac5888acc0f 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as String;
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
index c37a8bb39479..35b79a1d478c 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -215,7 +215,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as bool;
     }
     return null;
   }
@@ -349,7 +349,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as num;
     }
     return null;
   }
@@ -416,7 +416,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as String;
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
index 9f70d83f7eb0..0e8fe0845349 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
@@ -221,8 +221,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toList();
     }
     return null;
   }
@@ -298,8 +299,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return Set<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toSet();
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
index 8075bfea1e5a..918825ad38ed 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as String;
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
index c37a8bb39479..35b79a1d478c 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
@@ -215,7 +215,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as bool;
     }
     return null;
   }
@@ -349,7 +349,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as num;
     }
     return null;
   }
@@ -416,7 +416,7 @@ class FakeApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as String;
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
index 9f70d83f7eb0..0e8fe0845349 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
@@ -221,8 +221,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return List<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toList();
     }
     return null;
   }
@@ -298,8 +299,9 @@ class PetApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      final l = json.decode(response.body);
-      return Set<Pet>.of(l.map((model) => Pet.fromJson(model)));
+      return (json.decode(response.body) as List)
+        .map((i) => Pet.fromJson(i))
+        .toSet();
     }
     return null;
   }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
index 8075bfea1e5a..918825ad38ed 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
@@ -424,7 +424,7 @@ class UserApi {
     // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
     // FormatException when trying to decode an empty string.
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
-      return json.decode(response.body);
+      return response.body as String;
     }
     return null;
   }

From c5496dc939d8dd81a068b3193534b581effa2110 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Thu, 4 Mar 2021 21:20:44 +0000
Subject: [PATCH 7/9] Add json_serializable to maven modules

---
 pom.xml                                       |  1 +
 .../pom.xml                                   | 73 +++++++++++++++++++
 2 files changed, 74 insertions(+)
 create mode 100644 samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml

diff --git a/pom.xml b/pom.xml
index be57c37cbe19..2380cbdf094f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -1353,6 +1353,7 @@
                 <module>samples/client/petstore/dart2/petstore</module>
                 <module>samples/openapi3/client/petstore/dart2/petstore_client_lib</module>
                 <module>samples/openapi3/client/petstore/dart2/petstore</module>
+                <module>samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake</module>
                 <module>samples/client/petstore/dart-dio/petstore_client_lib</module>
                 <module>samples/openapi3/client/petstore/dart-dio/petstore_client_lib</module>
                 <module>samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake</module>
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml
new file mode 100644
index 000000000000..204b94074663
--- /dev/null
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml
@@ -0,0 +1,73 @@
+<project>
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>org.openapitools</groupId>
+    <artifactId>Dart2PetstoreClientJsonSerializableLibTests</artifactId>
+    <packaging>pom</packaging>
+    <version>1.0.0-SNAPSHOT</version>
+    <name>Dart2 Petstore Client with json_serializable Lib</name>
+    <build>
+        <plugins>
+            <plugin>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>copy-dependencies</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${project.build.directory}</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.2.1</version>
+                <executions>
+                    <execution>
+                        <id>export-dartfmt</id>
+                        <phase>pre-install-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>export</executable>
+                            <arguments>
+                                <argument>DART_FMT_PATH=/usr/local/bin/dartfmt</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>pub-get</id>
+                        <phase>pre-integration-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>pub</executable>
+                            <arguments>
+                                <argument>get</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>pub-test</id>
+                        <phase>integration-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>pub</executable>
+                            <arguments>
+                                <argument>run</argument>
+                                <argument>test</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

From f9e93e29888dae444ae33a05f8bdd774b3121d80 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Thu, 4 Mar 2021 21:58:13 +0000
Subject: [PATCH 8/9] Run build_runner before pub run test

---
 .../pom.xml                                       | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml
index 204b94074663..708ad4155156 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/pom.xml
@@ -52,6 +52,21 @@
                             </arguments>
                         </configuration>
                     </execution>
+                    <execution>
+                        <id>pub-build-runner</id>
+                        <phase>pre-integration-test</phase>
+                        <goals>
+                            <goal>exec</goal>
+                        </goals>
+                        <configuration>
+                            <executable>pub</executable>
+                            <arguments>
+                                <argument>run</argument>
+                                <argument>build_runner</argument>
+                                <argument>build</argument>
+                            </arguments>
+                        </configuration>
+                    </execution>
                     <execution>
                         <id>pub-test</id>
                         <phase>integration-test</phase>

From 7759ae1ebc2d8890c477c1868164338202778588 Mon Sep 17 00:00:00 2001
From: agilob <info@agilob.net>
Date: Wed, 10 Mar 2021 22:13:42 +0000
Subject: [PATCH 9/9] Return future of type for strong linter mode

---
 .../src/main/resources/dart2/api.mustache          |  2 +-
 .../dart2/petstore_client_lib/lib/api/pet_api.dart |  8 ++++----
 .../petstore_client_lib/lib/api/store_api.dart     |  6 +++---
 .../petstore_client_lib/lib/api/user_api.dart      |  4 ++--
 .../dart2/petstore_client_lib/lib/api/pet_api.dart | 12 ++++++------
 .../petstore_client_lib/lib/api/store_api.dart     |  6 +++---
 .../petstore_client_lib/lib/api/user_api.dart      |  4 ++--
 .../lib/api/another_fake_api.dart                  |  2 +-
 .../lib/api/default_api.dart                       |  2 +-
 .../petstore_client_lib_fake/lib/api/fake_api.dart | 14 +++++++-------
 .../lib/api/fake_classname_tags123_api.dart        |  2 +-
 .../petstore_client_lib_fake/lib/api/pet_api.dart  | 10 +++++-----
 .../lib/api/store_api.dart                         |  6 +++---
 .../petstore_client_lib_fake/lib/api/user_api.dart |  4 ++--
 .../lib/api/another_fake_api.dart                  |  2 +-
 .../lib/api/default_api.dart                       |  2 +-
 .../lib/api/fake_api.dart                          | 14 +++++++-------
 .../lib/api/fake_classname_tags123_api.dart        |  2 +-
 .../lib/api/pet_api.dart                           | 10 +++++-----
 .../lib/api/store_api.dart                         |  6 +++---
 .../lib/api/user_api.dart                          |  4 ++--
 21 files changed, 61 insertions(+), 61 deletions(-)

diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index c2ffc434b162..61ecab963b67 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -225,7 +225,7 @@ class {{{classname}}} {
     {{/isArray}}
     {{/json_serializable}}
     }
-    return Future.value(null);
+    return Future<{{{returnType}}}>.value(null);
     {{/returnType}}
   }
   {{/operation}}
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index baeed429b7de..c6446b856533 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -225,7 +225,7 @@ class PetApi {
         .cast<Pet>()
         .toList(growable: false);
     }
-    return Future.value(null);
+    return Future<List<Pet>>.value(null);
   }
 
   /// Finds Pets by tags
@@ -303,7 +303,7 @@ class PetApi {
         .cast<Pet>()
         .toList(growable: false);
     }
-    return Future.value(null);
+    return Future<List<Pet>>.value(null);
   }
 
   /// Find pet by ID
@@ -378,7 +378,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
         }
-    return Future.value(null);
+    return Future<Pet>.value(null);
   }
 
   /// Update an existing pet
@@ -626,6 +626,6 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
         }
-    return Future.value(null);
+    return Future<ApiResponse>.value(null);
   }
 }
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
index b80a441e5bb3..490860ed8c2f 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
@@ -139,7 +139,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
     }
-    return Future.value(null);
+    return Future<Map<String, int>>.value(null);
   }
 
   /// Find purchase order by ID
@@ -214,7 +214,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
         }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 
   /// Place an order for a pet
@@ -284,6 +284,6 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
         }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 }
diff --git a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index 26fe9da66aa2..f643e2e5dabf 100644
--- a/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -344,7 +344,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
         }
-    return Future.value(null);
+    return Future<User>.value(null);
   }
 
   /// Logs user into the system
@@ -426,7 +426,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
         }
-    return Future.value(null);
+    return Future<String>.value(null);
   }
 
   /// Logs out current logged in user session
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index 91e4ddf9ec17..2f9bc5863807 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -82,7 +82,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
         }
-    return Future.value(null);
+    return Future<Pet>.value(null);
   }
 
   /// Deletes a pet
@@ -232,7 +232,7 @@ class PetApi {
         .cast<Pet>()
         .toList(growable: false);
     }
-    return Future.value(null);
+    return Future<List<Pet>>.value(null);
   }
 
   /// Finds Pets by tags
@@ -310,7 +310,7 @@ class PetApi {
         .cast<Pet>()
         .toList(growable: false);
     }
-    return Future.value(null);
+    return Future<List<Pet>>.value(null);
   }
 
   /// Find pet by ID
@@ -385,7 +385,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
         }
-    return Future.value(null);
+    return Future<Pet>.value(null);
   }
 
   /// Update an existing pet
@@ -455,7 +455,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
         }
-    return Future.value(null);
+    return Future<Pet>.value(null);
   }
 
   /// Updates a pet in the store with form data
@@ -640,6 +640,6 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
         }
-    return Future.value(null);
+    return Future<ApiResponse>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
index 39000fbee581..76ffaec6faad 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
@@ -139,7 +139,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
     }
-    return Future.value(null);
+    return Future<Map<String, int>>.value(null);
   }
 
   /// Find purchase order by ID
@@ -214,7 +214,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
         }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 
   /// Place an order for a pet
@@ -284,6 +284,6 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
         }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index d391f692b150..08847cc2b07d 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -344,7 +344,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
         }
-    return Future.value(null);
+    return Future<User>.value(null);
   }
 
   /// Logs user into the system
@@ -426,7 +426,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
         }
-    return Future.value(null);
+    return Future<String>.value(null);
   }
 
   /// Logs out current logged in user session
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
index 6af794734a94..4dbc722ac178 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
@@ -86,6 +86,6 @@ class AnotherFakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
         }
-    return Future.value(null);
+    return Future<ModelClient>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
index 837b608bb36d..a75bdc33448e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
@@ -64,6 +64,6 @@ class DefaultApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'InlineResponseDefault') as InlineResponseDefault;
         }
-    return Future.value(null);
+    return Future<InlineResponseDefault>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
index 5bd1dcb319bb..d25c1bcd4a5e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -67,7 +67,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'HealthCheckResult') as HealthCheckResult;
         }
-    return Future.value(null);
+    return Future<HealthCheckResult>.value(null);
   }
 
   /// test http signature authentication
@@ -217,7 +217,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'bool') as bool;
         }
-    return Future.value(null);
+    return Future<bool>.value(null);
   }
 
   /// Test serialization of object with outer number type
@@ -284,7 +284,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'OuterComposite') as OuterComposite;
         }
-    return Future.value(null);
+    return Future<OuterComposite>.value(null);
   }
 
   /// Test serialization of outer number types
@@ -351,7 +351,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'num') as num;
         }
-    return Future.value(null);
+    return Future<num>.value(null);
   }
 
   /// Test serialization of outer string types
@@ -418,7 +418,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
         }
-    return Future.value(null);
+    return Future<String>.value(null);
   }
 
   /// Test serialization of enum (int) properties with examples
@@ -488,7 +488,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'OuterObjectWithEnumProperty') as OuterObjectWithEnumProperty;
         }
-    return Future.value(null);
+    return Future<OuterObjectWithEnumProperty>.value(null);
   }
 
   /// For this test, the body for this request much reference a schema named `File`.
@@ -688,7 +688,7 @@ class FakeApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
         }
-    return Future.value(null);
+    return Future<ModelClient>.value(null);
   }
 
   /// Fake endpoint for testing various parameters 假端點 偽のエンドポイント 가짜 엔드 포인트 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index b5ca1a09b0a9..0455f4c68f05 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -86,6 +86,6 @@ class FakeClassnameTags123Api {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ModelClient') as ModelClient;
         }
-    return Future.value(null);
+    return Future<ModelClient>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
index 71bafa7972c7..eacebcceace3 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
@@ -225,7 +225,7 @@ class PetApi {
         .cast<Pet>()
         .toList(growable: false);
     }
-    return Future.value(null);
+    return Future<List<Pet>>.value(null);
   }
 
   /// Finds Pets by tags
@@ -303,7 +303,7 @@ class PetApi {
         .cast<Pet>()
         .toSet();
     }
-    return Future.value(null);
+    return Future<Set<Pet>>.value(null);
   }
 
   /// Find pet by ID
@@ -378,7 +378,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Pet') as Pet;
         }
-    return Future.value(null);
+    return Future<Pet>.value(null);
   }
 
   /// Update an existing pet
@@ -626,7 +626,7 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
         }
-    return Future.value(null);
+    return Future<ApiResponse>.value(null);
   }
 
   /// uploads an image (required)
@@ -724,6 +724,6 @@ class PetApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'ApiResponse') as ApiResponse;
         }
-    return Future.value(null);
+    return Future<ApiResponse>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
index 9b750ca7bf45..91d115d44c83 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
@@ -139,7 +139,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return Map<String, int>.from(apiClient.deserialize(_decodeBodyBytes(response), 'Map<String, int>'));
     }
-    return Future.value(null);
+    return Future<Map<String, int>>.value(null);
   }
 
   /// Find purchase order by ID
@@ -214,7 +214,7 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
         }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 
   /// Place an order for a pet
@@ -284,6 +284,6 @@ class StoreApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'Order') as Order;
         }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
index eae48885150a..05ce7f9dec15 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
@@ -344,7 +344,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'User') as User;
         }
-    return Future.value(null);
+    return Future<User>.value(null);
   }
 
   /// Logs user into the system
@@ -426,7 +426,7 @@ class UserApi {
     if (response.body != null && response.statusCode != HttpStatus.noContent) {
       return apiClient.deserialize(_decodeBodyBytes(response), 'String') as String;
         }
-    return Future.value(null);
+    return Future<String>.value(null);
   }
 
   /// Logs out current logged in user session
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
index 34723cfc1ed2..29c7103abd37 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/another_fake_api.dart
@@ -87,6 +87,6 @@ class AnotherFakeApi {
 
       return ModelClient.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<ModelClient>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
index f8910210e2dd..6295891cd3cc 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/default_api.dart
@@ -65,6 +65,6 @@ class DefaultApi {
 
       return InlineResponseDefault.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<InlineResponseDefault>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
index e1554c5f0ca5..21c888fa5889 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_api.dart
@@ -68,7 +68,7 @@ class FakeApi {
 
       return HealthCheckResult.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<HealthCheckResult>.value(null);
   }
 
   /// test http signature authentication
@@ -219,7 +219,7 @@ class FakeApi {
 
       return response.body as bool;
     }
-    return Future.value(null);
+    return Future<bool>.value(null);
   }
 
   /// Test serialization of object with outer number type
@@ -287,7 +287,7 @@ class FakeApi {
 
       return OuterComposite.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<OuterComposite>.value(null);
   }
 
   /// Test serialization of outer number types
@@ -355,7 +355,7 @@ class FakeApi {
 
       return response.body as num;
     }
-    return Future.value(null);
+    return Future<num>.value(null);
   }
 
   /// Test serialization of outer string types
@@ -423,7 +423,7 @@ class FakeApi {
 
       return response.body as String;
     }
-    return Future.value(null);
+    return Future<String>.value(null);
   }
 
   /// Test serialization of enum (int) properties with examples
@@ -494,7 +494,7 @@ class FakeApi {
 
       return OuterObjectWithEnumProperty.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<OuterObjectWithEnumProperty>.value(null);
   }
 
   /// For this test, the body for this request much reference a schema named `File`.
@@ -695,7 +695,7 @@ class FakeApi {
 
       return ModelClient.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<ModelClient>.value(null);
   }
 
   /// Fake endpoint for testing various parameters 假端點 偽のエンドポイント 가짜 엔드 포인트 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index 96f44de5f1c4..dc0b394f8fb9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -87,6 +87,6 @@ class FakeClassnameTags123Api {
 
       return ModelClient.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<ModelClient>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
index 9b8baef0aa31..6c43311b2e8f 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/pet_api.dart
@@ -226,7 +226,7 @@ class PetApi {
         .map((i) => Pet.fromJson(i))
         .toList();
     }
-    return Future.value(null);
+    return Future<List<Pet>>.value(null);
   }
 
   /// Finds Pets by tags
@@ -305,7 +305,7 @@ class PetApi {
         .map((i) => Pet.fromJson(i))
         .toSet();
     }
-    return Future.value(null);
+    return Future<Set<Pet>>.value(null);
   }
 
   /// Find pet by ID
@@ -381,7 +381,7 @@ class PetApi {
 
       return Pet.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<Pet>.value(null);
   }
 
   /// Update an existing pet
@@ -630,7 +630,7 @@ class PetApi {
 
       return ApiResponse.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<ApiResponse>.value(null);
   }
 
   /// uploads an image (required)
@@ -729,6 +729,6 @@ class PetApi {
 
       return ApiResponse.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<ApiResponse>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
index cbd6cbf15202..dd5c2db3528e 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/store_api.dart
@@ -140,7 +140,7 @@ class StoreApi {
 
       return Map<String, int>.from(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<Map<String, int>>.value(null);
   }
 
   /// Find purchase order by ID
@@ -216,7 +216,7 @@ class StoreApi {
 
       return Order.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 
   /// Place an order for a pet
@@ -287,6 +287,6 @@ class StoreApi {
 
       return Order.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<Order>.value(null);
   }
 }
diff --git a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
index dae705e3c05d..ba21021c9ddb 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_json_serializable_client_lib_fake/lib/api/user_api.dart
@@ -345,7 +345,7 @@ class UserApi {
 
       return User.fromJson(json.decode(response.body));
     }
-    return Future.value(null);
+    return Future<User>.value(null);
   }
 
   /// Logs user into the system
@@ -428,7 +428,7 @@ class UserApi {
 
       return response.body as String;
     }
-    return Future.value(null);
+    return Future<String>.value(null);
   }
 
   /// Logs out current logged in user session