From 419493bf0c8ef7a3a45a274f69494f72109b5377 Mon Sep 17 00:00:00 2001
From: Marko Stojanovic <marko.stojanovic@fishingbooker.com>
Date: Mon, 6 Jul 2026 20:55:37 +0200
Subject: [PATCH] fix(typescript-fetch): skip scalar enum check for array-typed
 properties in instanceOf

  The instanceOf guard was emitting an invalid scalar !== comparison for
  required properties typed as Array<SingleValueEnum>, introduced as a
  side effect of PR #23497. The enum-literal check block now only fires
  for non-container (scalar) properties
---
 .../typescript-fetch/modelGeneric.mustache    |  2 ++
 .../TypeScriptFetchClientCodegenTest.java     | 15 +++++++++++
 .../array_of_single_value_enum.json           | 25 +++++++++++++++++++
 .../server/petstore/jaxrs-spec-enum/pom.xml   | 12 ++++++---
 4 files changed, 50 insertions(+), 4 deletions(-)
 create mode 100644 modules/openapi-generator/src/test/resources/3_0/typescript-fetch/array_of_single_value_enum.json

diff --git a/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache b/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache
index 4046fed3b286..2c3e6c8b150f 100644
--- a/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-fetch/modelGeneric.mustache
@@ -32,6 +32,7 @@ export function instanceOf{{classname}}(value: object): value is {{classname}} {
     if (!('{{name}}' in value) || value['{{name}}'] === undefined) return false;
     {{/hasSanitizedName}}
     {{#isEnum}}
+    {{^isContainer}}
     {{#allowableValues}}
     {{#values}}
     {{#-first}}
@@ -48,6 +49,7 @@ export function instanceOf{{classname}}(value: object): value is {{classname}} {
     {{/-first}}
     {{/values}}
     {{/allowableValues}}
+    {{/isContainer}}
     {{/isEnum}}
     {{/required}}
     {{/vars}}
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/fetch/TypeScriptFetchClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/fetch/TypeScriptFetchClientCodegenTest.java
index eafa46e33ce4..c5e4bde71e41 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/fetch/TypeScriptFetchClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/fetch/TypeScriptFetchClientCodegenTest.java
@@ -653,6 +653,21 @@ public void testNestedOneOfGeneratesTypeAliasForOneOfParent() throws IOException
         TestUtils.assertFileContains(outerPlain, "export interface OuterPlain {");
     }
 
+    @Test(description = "instanceOf guard must not emit scalar enum comparison for array-typed enum properties")
+    public void testInstanceOfArrayEnumNoScalarComparison() throws Exception {
+        File output = generate(
+            Collections.emptyMap(),
+            "src/test/resources/3_0/typescript-fetch/array_of_single_value_enum.json"
+        );
+
+        Path modelPath = Paths.get(output + "/models/TestSchema.ts");
+        // Must NOT emit a scalar !== comparison for an array-typed enum property
+        TestUtils.assertFileNotContains(modelPath, "value['types'] !== 'boatbooker_activities'");
+        TestUtils.assertFileNotContains(modelPath, "value['types'] !== boatbooker_activities");
+        // Must still check for presence of the field
+        TestUtils.assertFileContains(modelPath, "'types' in value");
+    }
+
     private static File generate(
         Map<String, Object> properties
     ) throws IOException {
diff --git a/modules/openapi-generator/src/test/resources/3_0/typescript-fetch/array_of_single_value_enum.json b/modules/openapi-generator/src/test/resources/3_0/typescript-fetch/array_of_single_value_enum.json
new file mode 100644
index 000000000000..f3d86539797a
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/typescript-fetch/array_of_single_value_enum.json
@@ -0,0 +1,25 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "title": "Array of Single-Value Enum Test",
+    "version": "1.0.0"
+  },
+  "paths": {},
+  "components": {
+    "schemas": {
+      "TestSchema": {
+        "required": ["types"],
+        "type": "object",
+        "properties": {
+          "types": {
+            "type": "array",
+            "items": {
+              "type": "string",
+              "enum": ["boatbooker_activities"]
+            }
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/samples/server/petstore/jaxrs-spec-enum/pom.xml b/samples/server/petstore/jaxrs-spec-enum/pom.xml
index 6d963d6dc72a..6f8ea7bbc4d2 100644
--- a/samples/server/petstore/jaxrs-spec-enum/pom.xml
+++ b/samples/server/petstore/jaxrs-spec-enum/pom.xml
@@ -37,9 +37,13 @@
             <failOnMissingWebXml>false</failOnMissingWebXml>
         </configuration>
       </plugin>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>3.5.6</version>
+      </plugin>
       <plugin>
         <artifactId>maven-failsafe-plugin</artifactId>
-        <version>2.6</version>
+        <version>3.5.6</version>
         <executions>
           <execution>
             <goals>
@@ -91,8 +95,8 @@
         <version>3.0.2</version>
     </dependency>
     <dependency>
-      <groupId>junit</groupId>
-      <artifactId>junit</artifactId>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-engine</artifactId>
       <version>${junit-version}</version>
       <scope>test</scope>
     </dependency>
@@ -135,7 +139,7 @@
     <maven.compiler.target>${java.version}</maven.compiler.target>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <jackson-version>2.19.2</jackson-version>
-    <junit-version>4.13.2</junit-version>
+    <junit-version>5.14.4</junit-version>
     <joda-version>2.10.13</joda-version>
     <javax.annotation-api-version>1.3.2</javax.annotation-api-version>
     <beanvalidation-version>2.0.2</beanvalidation-version>