Fix kotlin codegen for enum with int items (#22324)

Author: exviva

modules/openapi-generator/src/main/resources/kotlin-client/data_class.mustache

@@ -145,7 +145,7 @@ import {{packageName}}.infrastructure.ITransformForStorage
     {{#multiplatform}}
     @Serializable
     {{/multiplatform}}
-    {{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}enum class {{{nameInPascalCase}}}({{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val value: {{^isContainer}}{{dataType}}{{/isContainer}}{{#isContainer}}kotlin.String{{/isContainer}}) {
+    {{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}enum class {{{nameInPascalCase}}}({{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val value: {{^isContainer}}{{dataType}}{{/isContainer}}{{#isContainer}}{{#mostInnerItems}}{{dataType}}{{/mostInnerItems}}{{/isContainer}}) {
     {{#allowableValues}}
     {{#enumVars}}
         {{^multiplatform}}

modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinClientCodegenModelTest.java

@@ -43,6 +43,7 @@
 import java.util.Map;
 
 import static org.openapitools.codegen.CodegenConstants.*;
+import static org.openapitools.codegen.TestUtils.assertFileContains;
 
 @SuppressWarnings("static-method")
 public class KotlinClientCodegenModelTest {
@@ -617,6 +618,32 @@ public void polymorphicJacksonSerialization() throws IOException {
         TestUtils.assertFileNotContains(birdKt, "val discriminator");
     }
 
+  @Test
+  public void testIntArrayToEnum() throws IOException {
+      File output = Files.createTempDirectory("test").toFile();
+      output.deleteOnExit();
+
+      final CodegenConfigurator configurator = new CodegenConfigurator()
+              .setGeneratorName("kotlin")
+              .setLibrary("jvm-ktor")
+              .setAdditionalProperties(new HashMap<>() {{
+                put(CodegenConstants.SERIALIZATION_LIBRARY, "jackson");
+                put(CodegenConstants.MODEL_PACKAGE, "model");
+                put(ENUM_PROPERTY_NAMING, "UPPERCASE");
+              }})
+              .setInputSpec("src/test/resources/3_0/kotlin/issue15204-int-array-enum.yaml")
+              .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+      final ClientOptInput clientOptInput = configurator.toClientOptInput();
+      DefaultGenerator generator = new DefaultGenerator();
+
+      generator.opts(clientOptInput).generate();
+
+      final Path modelKt = Paths.get(output + "/src/main/kotlin/model/ModelWithIntArrayEnum.kt");
+
+      TestUtils.assertFileContains(modelKt, "enum class DaysOfWeek(val value: kotlin.Int)");
+  }
+
     private static class ModelNameTest {
         private final String expectedName;
         private final String expectedClassName;

modules/openapi-generator/src/test/resources/3_0/kotlin/issue15204-int-array-enum.yaml

@@ -0,0 +1,26 @@
+openapi: 3.0.0
+info:
+  title: 'Issue 15204 Int Array Enum'
+  version: latest
+paths:
+  '/':
+    get:
+      operationId: operation
+      responses:
+        '200':
+          description: Success
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ModelWithIntArrayEnum'
+components:
+  schemas:
+    ModelWithIntArrayEnum:
+      required:
+        - daysOfWeek
+      properties:
+        daysOfWeek:
+          type: array
+          items:
+            type: integer
+            enum: [0, 1, 2, 3, 4, 5, 6]