[BUG][JAVA][okhttp-gson] Skip validateJsonElement for ref'd enum properties

A property that is both isModel and isEnum (a $ref to a top-level enum
schema) was emitting MyEnum.validateJsonElement(...) inside the parent
class's validateJsonElement, which doesn't exist on enum classes and
breaks compilation. This is the same surface as #18547 narrowed to the
enum case.

Add an {{^isEnum}} guard inside the {{#isModel}} block so the call is
only emitted for non-enum models; the dedicated {{#isEnum}} branch
already below handles enum validation correctly.

Test: NullableFieldsMapResponse (anyOf wrapper of a success/error pair
with nullable required fields) added to the okhttp-gson fake petstore;
two JSONTest cases verify deserialization round-trips when nullable
required fields are null.

Refs #18547

Author: winrid

modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/pojo.mustache

@@ -434,6 +434,7 @@ public class {{classname}} {{#parent}}extends {{{.}}} {{/parent}}{{#vendorExtens
       }
       {{/isString}}
       {{#isModel}}
+      {{^isEnum}}
       {{#required}}
       {{#isNullable}}
       if (jsonObj.get("{{{baseName}}}") != null && !jsonObj.get("{{{baseName}}}").isJsonNull()) {
@@ -450,6 +451,7 @@ public class {{classname}} {{#parent}}extends {{{.}}} {{/parent}}{{#vendorExtens
         {{{dataType}}}.validateJsonElement(jsonObj.get("{{{baseName}}}"));
       }
       {{/required}}
+      {{/isEnum}}
       {{/isModel}}
       {{#isEnum}}
       {{#required}}

modules/openapi-generator/src/test/resources/3_0/java/petstore-with-fake-endpoints-models-for-testing-okhttp-gson.yaml

@@ -961,6 +961,20 @@ paths:
                   - type: array
                     items:
                       type: integer
+  /fake/nullable-required-fields-anyof:
+    get:
+      tags:
+        - fake
+      summary: test anyOf with map of objects containing nullable required fields
+      description: 'Tests that anyOf deserialization works when object values contain required fields that are nullable (e.g. Record<string, { before: string | null, after: string | null }>)'
+      operationId: testNullableRequiredFieldsAnyOf
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/NullableFieldsMapResponse'
   /fake/anyOfWIthSameErasure:
     get:
       description: Test route, this shouldn't cause a compiler error
@@ -2866,3 +2880,46 @@ components:
           allOf:
             - $ref: '#/components/schemas/Height'
           default: 32.1
+    NullableFieldsValue:
+      description: "Object with required but nullable string fields"
+      type: object
+      properties:
+        before:
+          type: string
+          nullable: true
+        after:
+          type: string
+          nullable: true
+      required:
+        - before
+        - after
+    NullableFieldsMapSuccess:
+      description: "Success response containing a map of objects with nullable fields"
+      type: object
+      additionalProperties: false
+      properties:
+        status:
+          type: string
+        positions:
+          type: object
+          additionalProperties:
+            $ref: '#/components/schemas/NullableFieldsValue'
+      required:
+        - status
+        - positions
+    NullableFieldsMapError:
+      description: "Error response"
+      type: object
+      additionalProperties: false
+      properties:
+        status:
+          type: string
+        reason:
+          type: string
+      required:
+        - status
+        - reason
+    NullableFieldsMapResponse:
+      anyOf:
+        - $ref: '#/components/schemas/NullableFieldsMapSuccess'
+        - $ref: '#/components/schemas/NullableFieldsMapError'

samples/client/petstore/java/okhttp-gson/.openapi-generator/FILES

@@ -80,6 +80,10 @@ docs/NewPetCategoryInlineAllof.md
 docs/NewPetCategoryInlineAllofAllOfCategoryTag.md
 docs/NullableClass.md
 docs/NullableEnum.md
+docs/NullableFieldsMapError.md
+docs/NullableFieldsMapResponse.md
+docs/NullableFieldsMapSuccess.md
+docs/NullableFieldsValue.md
 docs/NullableShape.md
 docs/NumberOnly.md
 docs/ObjectWithDeprecatedFields.md
@@ -231,6 +235,10 @@ src/main/java/org/openapitools/client/model/NewPetCategoryInlineAllof.java
 src/main/java/org/openapitools/client/model/NewPetCategoryInlineAllofAllOfCategoryTag.java
 src/main/java/org/openapitools/client/model/NullableClass.java
 src/main/java/org/openapitools/client/model/NullableEnum.java
+src/main/java/org/openapitools/client/model/NullableFieldsMapError.java
+src/main/java/org/openapitools/client/model/NullableFieldsMapResponse.java
+src/main/java/org/openapitools/client/model/NullableFieldsMapSuccess.java
+src/main/java/org/openapitools/client/model/NullableFieldsValue.java
 src/main/java/org/openapitools/client/model/NullableShape.java
 src/main/java/org/openapitools/client/model/NumberOnly.java
 src/main/java/org/openapitools/client/model/ObjectWithDeprecatedFields.java
@@ -269,3 +277,7 @@ src/main/java/org/openapitools/client/model/Value.java
 src/main/java/org/openapitools/client/model/Variable.java
 src/main/java/org/openapitools/client/model/Whale.java
 src/main/java/org/openapitools/client/model/Zebra.java
+src/test/java/org/openapitools/client/model/NullableFieldsMapErrorTest.java
+src/test/java/org/openapitools/client/model/NullableFieldsMapResponseTest.java
+src/test/java/org/openapitools/client/model/NullableFieldsMapSuccessTest.java
+src/test/java/org/openapitools/client/model/NullableFieldsValueTest.java

samples/client/petstore/java/okhttp-gson/README.md

@@ -142,6 +142,7 @@ Class | Method | HTTP request | Description
 *FakeApi* | [**testInlineAdditionalProperties**](docs/FakeApi.md#testInlineAdditionalProperties) | **POST** /fake/inline-additionalProperties | test inline additionalProperties
 *FakeApi* | [**testInlineFreeformAdditionalProperties**](docs/FakeApi.md#testInlineFreeformAdditionalProperties) | **POST** /fake/inline-freeform-additionalProperties | test inline free-form additionalProperties
 *FakeApi* | [**testJsonFormData**](docs/FakeApi.md#testJsonFormData) | **GET** /fake/jsonFormData | test json serialization of form data
+*FakeApi* | [**testNullableRequiredFieldsAnyOf**](docs/FakeApi.md#testNullableRequiredFieldsAnyOf) | **GET** /fake/nullable-required-fields-anyof | test anyOf with map of objects containing nullable required fields
 *FakeApi* | [**testQueryParameterCollectionFormat**](docs/FakeApi.md#testQueryParameterCollectionFormat) | **PUT** /fake/test-query-parameters | 
 *FakeApi* | [**testStringMapReference**](docs/FakeApi.md#testStringMapReference) | **POST** /fake/stringMap-reference | test referenced string map
 *FakeClassnameTags123Api* | [**testClassname**](docs/FakeClassnameTags123Api.md#testClassname) | **PATCH** /fake_classname_test | To test class name in snake case
@@ -242,6 +243,10 @@ Class | Method | HTTP request | Description
  - [NewPetCategoryInlineAllofAllOfCategoryTag](docs/NewPetCategoryInlineAllofAllOfCategoryTag.md)
  - [NullableClass](docs/NullableClass.md)
  - [NullableEnum](docs/NullableEnum.md)
+ - [NullableFieldsMapError](docs/NullableFieldsMapError.md)
+ - [NullableFieldsMapResponse](docs/NullableFieldsMapResponse.md)
+ - [NullableFieldsMapSuccess](docs/NullableFieldsMapSuccess.md)
+ - [NullableFieldsValue](docs/NullableFieldsValue.md)
  - [NullableShape](docs/NullableShape.md)
  - [NumberOnly](docs/NumberOnly.md)
  - [ObjectWithDeprecatedFields](docs/ObjectWithDeprecatedFields.md)

samples/client/petstore/java/okhttp-gson/api/openapi.yaml

@@ -1021,6 +1021,24 @@ paths:
           description: successful response
       x-accepts:
       - application/json
+  /fake/nullable-required-fields-anyof:
+    get:
+      description: "Tests that anyOf deserialization works when object values contain\
+        \ required fields that are nullable (e.g. Record<string, { before: string\
+        \ | null, after: string | null }>)"
+      operationId: testNullableRequiredFieldsAnyOf
+      responses:
+        "200":
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/NullableFieldsMapResponse"
+          description: successful operation
+      summary: test anyOf with map of objects containing nullable required fields
+      tags:
+      - fake
+      x-accepts:
+      - application/json
   /fake/anyOfWIthSameErasure:
     get:
       description: "Test route, this shouldn't cause a compiler error"
@@ -2998,6 +3016,58 @@ components:
           - $ref: "#/components/schemas/Height"
           default: 32.1
       type: object
+    NullableFieldsValue:
+      description: Object with required but nullable string fields
+      example:
+        before: before
+        after: after
+      properties:
+        before:
+          nullable: true
+          type: string
+        after:
+          nullable: true
+          type: string
+      required:
+      - after
+      - before
+      type: object
+    NullableFieldsMapSuccess:
+      additionalProperties: false
+      description: Success response containing a map of objects with nullable fields
+      example:
+        positions:
+          key:
+            before: before
+            after: after
+        status: status
+      properties:
+        status:
+          type: string
+        positions:
+          additionalProperties:
+            $ref: "#/components/schemas/NullableFieldsValue"
+          type: object
+      required:
+      - positions
+      - status
+      type: object
+    NullableFieldsMapError:
+      additionalProperties: false
+      description: Error response
+      properties:
+        status:
+          type: string
+        reason:
+          type: string
+      required:
+      - reason
+      - status
+      type: object
+    NullableFieldsMapResponse:
+      anyOf:
+      - $ref: "#/components/schemas/NullableFieldsMapSuccess"
+      - $ref: "#/components/schemas/NullableFieldsMapError"
     _foo_get_default_response:
       example:
         string:

samples/client/petstore/java/okhttp-gson/docs/FakeApi.md

@@ -25,6 +25,7 @@ All URIs are relative to *http://petstore.swagger.io:80/v2*
 | [**testInlineAdditionalProperties**](FakeApi.md#testInlineAdditionalProperties) | **POST** /fake/inline-additionalProperties | test inline additionalProperties |
 | [**testInlineFreeformAdditionalProperties**](FakeApi.md#testInlineFreeformAdditionalProperties) | **POST** /fake/inline-freeform-additionalProperties | test inline free-form additionalProperties |
 | [**testJsonFormData**](FakeApi.md#testJsonFormData) | **GET** /fake/jsonFormData | test json serialization of form data |
+| [**testNullableRequiredFieldsAnyOf**](FakeApi.md#testNullableRequiredFieldsAnyOf) | **GET** /fake/nullable-required-fields-anyof | test anyOf with map of objects containing nullable required fields |
 | [**testQueryParameterCollectionFormat**](FakeApi.md#testQueryParameterCollectionFormat) | **PUT** /fake/test-query-parameters |  |
 | [**testStringMapReference**](FakeApi.md#testStringMapReference) | **POST** /fake/stringMap-reference | test referenced string map |
 
@@ -1380,6 +1381,64 @@ No authorization required
 |-------------|-------------|------------------|
 | **200** | successful operation |  -  |
 
+<a id="testNullableRequiredFieldsAnyOf"></a>
+# **testNullableRequiredFieldsAnyOf**
+> NullableFieldsMapResponse testNullableRequiredFieldsAnyOf()
+
+test anyOf with map of objects containing nullable required fields
+
+Tests that anyOf deserialization works when object values contain required fields that are nullable (e.g. Record&lt;string, { before: string | null, after: string | null }&gt;)
+
+### Example
+```java
+// Import classes:
+import org.openapitools.client.ApiClient;
+import org.openapitools.client.ApiException;
+import org.openapitools.client.Configuration;
+import org.openapitools.client.models.*;
+import org.openapitools.client.api.FakeApi;
+
+public class Example {
+  public static void main(String[] args) {
+    ApiClient defaultClient = Configuration.getDefaultApiClient();
+    defaultClient.setBasePath("http://petstore.swagger.io:80/v2");
+
+    FakeApi apiInstance = new FakeApi(defaultClient);
+    try {
+      NullableFieldsMapResponse result = apiInstance.testNullableRequiredFieldsAnyOf();
+      System.out.println(result);
+    } catch (ApiException e) {
+      System.err.println("Exception when calling FakeApi#testNullableRequiredFieldsAnyOf");
+      System.err.println("Status code: " + e.getCode());
+      System.err.println("Reason: " + e.getResponseBody());
+      System.err.println("Response headers: " + e.getResponseHeaders());
+      e.printStackTrace();
+    }
+  }
+}
+```
+
+### Parameters
+This endpoint does not need any parameter.
+
+### Return type
+
+[**NullableFieldsMapResponse**](NullableFieldsMapResponse.md)
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: Not defined
+ - **Accept**: application/json
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+| **200** | successful operation |  -  |
+
 <a id="testQueryParameterCollectionFormat"></a>
 # **testQueryParameterCollectionFormat**
 > testQueryParameterCollectionFormat(pipe, ioutil, http, url, context)

samples/client/petstore/java/okhttp-gson/docs/NullableFieldsMapError.md

@@ -0,0 +1,15 @@
+
+
+# NullableFieldsMapError
+
+Error response
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**status** | **String** |  |  |
+|**reason** | **String** |  |  |
+
+
+

samples/client/petstore/java/okhttp-gson/docs/NullableFieldsMapResponse.md

@@ -0,0 +1,15 @@
+
+
+# NullableFieldsMapResponse
+
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**status** | **String** |  |  |
+|**positions** | [**Map<String, NullableFieldsValue>**](NullableFieldsValue.md) |  |  |
+|**reason** | **String** |  |  |
+
+
+

samples/client/petstore/java/okhttp-gson/docs/NullableFieldsMapSuccess.md

@@ -0,0 +1,15 @@
+
+
+# NullableFieldsMapSuccess
+
+Success response containing a map of objects with nullable fields
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**status** | **String** |  |  |
+|**positions** | [**Map<String, NullableFieldsValue>**](NullableFieldsValue.md) |  |  |
+
+
+

samples/client/petstore/java/okhttp-gson/docs/NullableFieldsValue.md

@@ -0,0 +1,15 @@
+
+
+# NullableFieldsValue
+
+Object with required but nullable string fields
+
+## Properties
+
+| Name | Type | Description | Notes |
+|------------ | ------------- | ------------- | -------------|
+|**before** | **String** |  |  |
+|**after** | **String** |  |  |
+
+
+