fix(InlineModelResolver): do not merge distinct inline enums sharing the same values

The structural-signature fallback added in #23856 strips 'description',
'type' and 'example' before comparing schemas so that multi-file $ref
object schemas mutated by the parser still deduplicate. For enum schemas
this is too aggressive: two enums that list the same values but mean
different things are distinguished only by their description, so stripping
it wrongly unifies them and the second usage silently reuses the first
enum's type (regression in 7.23.0, worked in 7.22.0).

Skip the structural fallback for enum schemas in matchGenerated() so enums
deduplicate on exact content only. Object-schema multi-file dedup is
unaffected.

Fixes #23978

Author: seonwooj0810

modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java

@@ -849,6 +849,10 @@ private String resolveModelName(String title, String modelName) {
         }
     }
 
+    private static boolean isEnumSchema(Schema model) {
+        return model != null && model.getEnum() != null && !model.getEnum().isEmpty();
+    }
+
     private String matchGenerated(Schema model) {
         if (skipSchemaReuse) { // skip reusing schema
             return null;
@@ -862,9 +866,18 @@ private String matchGenerated(Schema model) {
             }
             // Structural match: compare with volatile fields stripped at every level.
             // See generatedStructuralSignature field for a full explanation of why this is needed.
-            String structural = computeStructuralSignature(model);
-            if (generatedStructuralSignature.containsKey(structural)) {
-                return generatedStructuralSignature.get(structural);
+            //
+            // Skip this fallback for enum schemas: the structural matcher strips 'description',
+            // but for an enum the description is the only thing distinguishing two schemas that
+            // share the same values yet represent different things (e.g. two properties whose
+            // enums happen to list the same values but mean different things). Stripping it would
+            // wrongly unify them and make the second usage silently reuse the first enum's type
+            // (#23978). Enum schemas therefore dedup on exact content only.
+            if (!isEnumSchema(model)) {
+                String structural = computeStructuralSignature(model);
+                if (generatedStructuralSignature.containsKey(structural)) {
+                    return generatedStructuralSignature.get(structural);
+                }
             }
         } catch (JsonProcessingException e) {
             e.printStackTrace();

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

@@ -1385,6 +1385,45 @@ public void resolveInlineModelDeduplicatesWhenParserMutatesPropertyTypes() {
                 schemas.get("StorageBackend_1"));
     }
 
+    @Test
+    public void doNotMergeDistinctInlineEnumsSharingTheSameValues() {
+        // Regression test for #23978: two inline enum properties that share the same enum values
+        // but represent different things (distinguished only by their description) must each be
+        // promoted to their own schema.  The structural-signature fallback in matchGenerated()
+        // strips 'description', so without an enum guard it would wrongly unify them and the
+        // second property would silently reuse the first enum's type (regression in 7.23.0).
+        OpenAPI openapi = new OpenAPI();
+        openapi.setComponents(new Components());
+        openapi.setPaths(new Paths());
+
+        StringSchema statusEnum = new StringSchema();
+        statusEnum.setDescription("Lifecycle status of the order");
+        statusEnum.setEnum(java.util.Arrays.asList("ACTIVE", "INACTIVE"));
+
+        StringSchema visibilityEnum = new StringSchema();
+        visibilityEnum.setDescription("Whether the order is visible to the customer");
+        visibilityEnum.setEnum(java.util.Arrays.asList("ACTIVE", "INACTIVE"));
+
+        openapi.getComponents().addSchemas("Order", new ObjectSchema()
+                .title("Order")
+                .addProperty("status", statusEnum)
+                .addProperty("visibility", visibilityEnum));
+
+        InlineModelResolver resolver = new InlineModelResolver();
+        Map<String, String> options = new HashMap<>();
+        options.put("RESOLVE_INLINE_ENUMS", "true");
+        resolver.setInlineSchemaOptions(options);
+        resolver.flatten(openapi);
+
+        Schema order = openapi.getComponents().getSchemas().get("Order");
+        String statusRef = ((Schema) order.getProperties().get("status")).get$ref();
+        String visibilityRef = ((Schema) order.getProperties().get("visibility")).get$ref();
+        assertNotNull("status enum must be promoted to its own schema", statusRef);
+        assertNotNull("visibility enum must be promoted to its own schema", visibilityRef);
+        assertFalse("Distinct inline enums sharing the same values must not be merged (#23978)",
+                statusRef.equals(visibilityRef));
+    }
+
     @Test
     public void deduplicateComponentsRemovesNumberedDuplicateOfTitledSchemaAndRewritesRefs() {
         // Regression test: when flattening creates a numbered duplicate of a titled component

samples/client/petstore/csharp/generichost/net10/FormModels/.openapi-generator/FILES

@@ -121,6 +121,7 @@ docs/models/TestCollectionEndingWithWordList.md
 docs/models/TestCollectionEndingWithWordListObject.md
 docs/models/TestDescendants.md
 docs/models/TestDescendantsObjectType.md
+docs/models/TestEnumParametersEnumHeaderStringParameter.md
 docs/models/TestEnumParametersEnumQueryDoubleParameter.md
 docs/models/TestEnumParametersEnumQueryIntegerParameter.md
 docs/models/TestEnumParametersRequestEnumFormString.md
@@ -140,6 +141,7 @@ docs/models/ZeroBasedEnumClassZeroBasedEnum.md
 docs/scripts/git_push.ps1
 docs/scripts/git_push.sh
 src/Org.OpenAPITools.Test/Api/DependencyInjectionTests.cs
+src/Org.OpenAPITools.Test/Model/TestEnumParametersEnumHeaderStringParameterTests.cs
 src/Org.OpenAPITools.Test/Org.OpenAPITools.Test.csproj
 src/Org.OpenAPITools.Test/README.md
 src/Org.OpenAPITools/Api/AnotherFakeApi.cs
@@ -289,6 +291,7 @@ src/Org.OpenAPITools/Model/TestCollectionEndingWithWordList.cs
 src/Org.OpenAPITools/Model/TestCollectionEndingWithWordListObject.cs
 src/Org.OpenAPITools/Model/TestDescendants.cs
 src/Org.OpenAPITools/Model/TestDescendantsObjectType.cs
+src/Org.OpenAPITools/Model/TestEnumParametersEnumHeaderStringParameter.cs
 src/Org.OpenAPITools/Model/TestEnumParametersEnumQueryDoubleParameter.cs
 src/Org.OpenAPITools/Model/TestEnumParametersEnumQueryIntegerParameter.cs
 src/Org.OpenAPITools/Model/TestEnumParametersRequestEnumFormString.cs

samples/client/petstore/csharp/generichost/net10/FormModels/api/openapi.yaml

@@ -772,7 +772,7 @@ paths:
         name: enum_header_string
         required: false
         schema:
-          $ref: "#/components/schemas/testEnumParameters_request_enum_form_string"
+          $ref: "#/components/schemas/testEnumParameters_enum_header_string_parameter"
         style: simple
       - description: Query parameter enum test (string array)
         explode: true
@@ -790,7 +790,7 @@ paths:
         name: enum_query_string
         required: false
         schema:
-          $ref: "#/components/schemas/testEnumParameters_request_enum_form_string"
+          $ref: "#/components/schemas/testEnumParameters_enum_header_string_parameter"
         style: form
       - description: Query parameter enum test (double)
         explode: true
@@ -2819,6 +2819,13 @@ components:
         enum_form_string:
           $ref: "#/components/schemas/testEnumParameters_request_enum_form_string"
       type: object
+    testEnumParameters_enum_header_string_parameter:
+      default: -efg
+      enum:
+      - _abc
+      - -efg
+      - (xyz)
+      type: string
     testEnumParameters_enum_query_integer_parameter:
       enum:
       - 1

samples/client/petstore/csharp/generichost/net10/FormModels/docs/apis/FakeApi.md

@@ -483,7 +483,7 @@ void (empty response body)
 
 <a id="testenumparameters"></a>
 # **TestEnumParameters**
-> void TestEnumParameters (TestEnumParametersRequestEnumFormString enumFormString = null, List<TestEnumParametersRequestEnumFormStringArrayInner> enumFormStringArray = null, TestEnumParametersRequestEnumFormString enumHeaderString = null, List<TestEnumParametersRequestEnumFormStringArrayInner> enumHeaderStringArray = null, TestEnumParametersEnumQueryDoubleParameter enumQueryDouble = null, TestEnumParametersEnumQueryIntegerParameter enumQueryInteger = null, TestEnumParametersRequestEnumFormString enumQueryString = null, List<TestEnumParametersRequestEnumFormStringArrayInner> enumQueryStringArray = null)
+> void TestEnumParameters (TestEnumParametersRequestEnumFormString enumFormString = null, List<TestEnumParametersRequestEnumFormStringArrayInner> enumFormStringArray = null, TestEnumParametersEnumHeaderStringParameter enumHeaderString = null, List<TestEnumParametersRequestEnumFormStringArrayInner> enumHeaderStringArray = null, TestEnumParametersEnumQueryDoubleParameter enumQueryDouble = null, TestEnumParametersEnumQueryIntegerParameter enumQueryInteger = null, TestEnumParametersEnumHeaderStringParameter enumQueryString = null, List<TestEnumParametersRequestEnumFormStringArrayInner> enumQueryStringArray = null)
 
 To test enum parameters
 
@@ -496,11 +496,11 @@ To test enum parameters
 |------|------|-------------|-------|
 | **enumFormString** | **TestEnumParametersRequestEnumFormString** |  | [optional]  |
 | **enumFormStringArray** | [**List&lt;TestEnumParametersRequestEnumFormStringArrayInner&gt;**](TestEnumParametersRequestEnumFormStringArrayInner.md) | Form parameter enum test (string array) | [optional]  |
-| **enumHeaderString** | **TestEnumParametersRequestEnumFormString** | Header parameter enum test (string) | [optional]  |
+| **enumHeaderString** | **TestEnumParametersEnumHeaderStringParameter** | Header parameter enum test (string) | [optional]  |
 | **enumHeaderStringArray** | [**List&lt;TestEnumParametersRequestEnumFormStringArrayInner&gt;**](TestEnumParametersRequestEnumFormStringArrayInner.md) | Header parameter enum test (string array) | [optional]  |
 | **enumQueryDouble** | **TestEnumParametersEnumQueryDoubleParameter** | Query parameter enum test (double) | [optional]  |
 | **enumQueryInteger** | **TestEnumParametersEnumQueryIntegerParameter** | Query parameter enum test (double) | [optional]  |
-| **enumQueryString** | **TestEnumParametersRequestEnumFormString** | Query parameter enum test (string) | [optional]  |
+| **enumQueryString** | **TestEnumParametersEnumHeaderStringParameter** | Query parameter enum test (string) | [optional]  |
 | **enumQueryStringArray** | [**List&lt;TestEnumParametersRequestEnumFormStringArrayInner&gt;**](TestEnumParametersRequestEnumFormStringArrayInner.md) | Query parameter enum test (string array) | [optional]  |
 
 ### Return type

samples/client/petstore/csharp/generichost/net10/FormModels/docs/models/TestEnumParametersEnumHeaderStringParameter.md

@@ -0,0 +1,9 @@
+# Org.OpenAPITools.Model.TestEnumParametersEnumHeaderStringParameter
+
+## Properties
+
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+
+[[Back to Model list]](../../README.md#documentation-for-models) [[Back to API list]](../../README.md#documentation-for-api-endpoints) [[Back to README]](../../README.md)
+

samples/client/petstore/csharp/generichost/net10/FormModels/src/Org.OpenAPITools.Test/Model/TestEnumParametersEnumHeaderStringParameterTests.cs

@@ -0,0 +1,56 @@
+/*
+ * OpenAPI Petstore
+ *
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+
+using Xunit;
+
+using System;
+using System.Linq;
+using System.IO;
+using System.Collections.Generic;
+using Org.OpenAPITools.Model;
+using Org.OpenAPITools.Client;
+using System.Reflection;
+
+namespace Org.OpenAPITools.Test.Model
+{
+    /// <summary>
+    ///  Class for testing TestEnumParametersEnumHeaderStringParameter
+    /// </summary>
+    /// <remarks>
+    /// This file is automatically generated by OpenAPI Generator (https://openapi-generator.tech).
+    /// Please update the test case below to test the model.
+    /// </remarks>
+    public class TestEnumParametersEnumHeaderStringParameterTests : IDisposable
+    {
+        // TODO uncomment below to declare an instance variable for TestEnumParametersEnumHeaderStringParameter
+        //private TestEnumParametersEnumHeaderStringParameter instance;
+
+        public TestEnumParametersEnumHeaderStringParameterTests()
+        {
+            // TODO uncomment below to create an instance of TestEnumParametersEnumHeaderStringParameter
+            //instance = new TestEnumParametersEnumHeaderStringParameter();
+        }
+
+        public void Dispose()
+        {
+            // Cleanup when everything is done.
+        }
+
+        /// <summary>
+        /// Test an instance of TestEnumParametersEnumHeaderStringParameter
+        /// </summary>
+        [Fact]
+        public void TestEnumParametersEnumHeaderStringParameterInstanceTest()
+        {
+            // TODO uncomment below to test "IsType" TestEnumParametersEnumHeaderStringParameter
+            //Assert.IsType<TestEnumParametersEnumHeaderStringParameter>(instance);
+        }
+    }
+}