[Java] Declare the inline discriminator enum in oneOf interfaces

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

@@ -835,6 +835,27 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
             }
         }
 
+        // A oneOf interface declares the inline enum of its own discriminator (oneof_interface.mustache) and the
+        // implementors inherit it. A property in an implementor's allVars is its own and keeps its enum.
+        if (useOneOfInterfaces && !(this instanceof GroovyClientCodegen)) {
+            for (CodegenModel cm : allModels.values()) {
+                for (CodegenProperty disc : cm.vars) {
+                    boolean fromImplementors = cm.interfaceModels != null && cm.interfaceModels.stream()
+                            .flatMap(m -> m.allVars.stream())
+                            .anyMatch(v -> disc.baseName.equals(v.baseName));
+                    if (cm.oneOf.isEmpty() || !disc.isDiscriminator || !disc.isEnum) continue;
+                    if (fromImplementors) {
+                        disc.isEnum = false;
+                        continue;
+                    }
+                    cm.oneOf.stream().map(allModels::get).filter(Objects::nonNull)
+                            .flatMap(impl -> impl.vars.stream())
+                            .filter(v -> disc.baseName.equals(v.baseName))
+                            .forEach(v -> v.isEnum = false);
+                }
+            }
+        }
+
         if (isGenerateConstructorWithAllArgs()) {
             // conditionally force the generation of all args constructor.
             for (CodegenModel cm : allModels.values()) {

modules/openapi-generator/src/main/resources/Java/oneof_interface.mustache

@@ -3,6 +3,13 @@
 {{{.}}}
 {{/vendorExtensions.x-class-extra-annotation}}
 public {{>sealed}}interface {{classname}} {{#vendorExtensions.x-implements}}{{#-first}}extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{#-last}} {{/-last}}{{/vendorExtensions.x-implements}}{{>permits}}{
+    {{#vars}}
+    {{#isEnum}}
+    {{#isDiscriminator}}
+{{>modelInnerEnum}}
+    {{/isDiscriminator}}
+    {{/isEnum}}
+    {{/vars}}
     {{#discriminator}}
     public {{propertyType}} {{propertyGetter}}();
     {{/discriminator}}

modules/openapi-generator/src/main/resources/Java/pojo_doc.mustache

@@ -8,17 +8,17 @@
 
 | Name | Type | Description | Notes |
 |------------ | ------------- | ------------- | -------------|
-{{#vars}}|**{{name}}** | {{#isEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isEnum}}{{^isEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
+{{#vars}}|**{{name}}** | {{#isInnerEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isInnerEnum}}{{^isInnerEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isInnerEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
 {{/vars}}
-{{#vars}}{{#isEnum}}
+{{#vars}}{{#isInnerEnum}}
 
 
 ## Enum: {{datatypeWithEnum}}
 
 | Name | Value |
 |---- | -----|{{#allowableValues}}{{#enumVars}}
 | {{name}} | {{value}} |{{/enumVars}}{{/allowableValues}}
-{{/isEnum}}{{/vars}}
+{{/isInnerEnum}}{{/vars}}
 {{#vendorExtensions.x-implements.0}}
 
 ## Implemented Interfaces

modules/openapi-generator/src/main/resources/JavaJaxRS/spec/oneof_interface.mustache

@@ -1,3 +1,21 @@
+{{#vars}}
+{{#isEnum}}
+{{#isDiscriminator}}
+{{#jackson}}
+import com.fasterxml.jackson.annotation.*;
+{{/jackson}}
+{{#jsonb}}
+import {{javaxPackage}}.json.bind.annotation.*;
+import {{javaxPackage}}.json.bind.serializer.*;
+import {{javaxPackage}}.json.stream.*;
+{{/jsonb}}
+{{#withXml}}
+import {{javaxPackage}}.xml.bind.annotation.*;
+{{/withXml}}
+{{/isDiscriminator}}
+{{/isEnum}}
+{{/vars}}
+
 {{>additionalOneOfTypeAnnotations}}
 {{#discriminator}}
 {{>typeInfoAnnotation}}
@@ -15,6 +33,13 @@
 {{>generatedAnnotation}}
 
 public {{>sealed}}interface {{classname}}{{#vendorExtensions.x-implements}}{{#-first}} extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{/vendorExtensions.x-implements}} {{>permits}}{
+    {{#vars}}
+    {{#isEnum}}
+    {{#isDiscriminator}}
+{{>enumClass}}
+    {{/isDiscriminator}}
+    {{/isEnum}}
+    {{/vars}}
     {{#discriminator}}
     {{propertyType}} {{propertyGetter}}();
     {{/discriminator}}

modules/openapi-generator/src/main/resources/JavaSpring/oneof_interface.mustache

@@ -21,6 +21,13 @@
 {{>generatedAnnotation}}
 
 public {{>sealed}}interface {{classname}}{{#vendorExtensions.x-implements}}{{#-first}} extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{/vendorExtensions.x-implements}} {{>permits}}{
+    {{#vars}}
+    {{#isEnum}}
+    {{#isDiscriminator}}
+{{>enumClass}}
+    {{/isDiscriminator}}
+    {{/isEnum}}
+    {{/vars}}
     {{#discriminator}}
     public {{propertyType}} {{propertyGetter}}();
     {{/discriminator}}

modules/openapi-generator/src/main/resources/java-helidon/client/libraries/mp/oneof_interface.mustache

@@ -1,5 +1,12 @@
 {{>additionalOneOfTypeAnnotations}}{{>generatedAnnotation}}{{>typeInfoAnnotation}}{{>xmlAnnotation}}
 public interface {{classname}} {{#vendorExtensions.x-implements}}{{#-first}}extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{/vendorExtensions.x-implements}} {
+    {{#vars}}
+    {{#isEnum}}
+    {{#isDiscriminator}}
+{{>enumClass}}
+    {{/isDiscriminator}}
+    {{/isEnum}}
+    {{/vars}}
     {{#discriminator}}
     public {{propertyType}} {{propertyGetter}}();
     {{/discriminator}}

modules/openapi-generator/src/main/resources/java-helidon/client/libraries/mp/pojo_doc.mustache

@@ -8,17 +8,17 @@
 
 | Name | Type | Description | Notes |
 |------------ | ------------- | ------------- | -------------|
-{{#vars}}|**{{name}}** | {{#isEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isEnum}}{{^isEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
+{{#vars}}|**{{name}}** | {{#isInnerEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isInnerEnum}}{{^isInnerEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isInnerEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
 {{/vars}}
-{{#vars}}{{#isEnum}}
+{{#vars}}{{#isInnerEnum}}
 
 
 ## Enum: {{datatypeWithEnum}}
 
 | Name | Value |
 |---- | -----|{{#allowableValues}}{{#enumVars}}
 | {{name}} | {{value}} |{{/enumVars}}{{/allowableValues}}
-{{/isEnum}}{{/vars}}
+{{/isInnerEnum}}{{/vars}}
 {{#vendorExtensions.x-implements.0}}
 
 ## Implemented Interfaces

modules/openapi-generator/src/main/resources/java-helidon/client/libraries/se/oneof_interface.mustache

@@ -1,5 +1,12 @@
 {{>additionalOneOfTypeAnnotations}}{{>generatedAnnotation}}{{>typeInfoAnnotation}}{{>xmlAnnotation}}
 public interface {{classname}} {{#vendorExtensions.x-implements}}{{#-first}}extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{/vendorExtensions.x-implements}} {
+    {{#vars}}
+    {{#isEnum}}
+    {{#isDiscriminator}}
+{{>enumClass}}
+    {{/isDiscriminator}}
+    {{/isEnum}}
+    {{/vars}}
     {{#discriminator}}
     public {{propertyType}} {{propertyGetter}}();
     {{/discriminator}}

modules/openapi-generator/src/main/resources/java-helidon/client/libraries/se/pojo_doc.mustache

@@ -8,17 +8,17 @@
 
 | Name | Type | Description | Notes |
 |------------ | ------------- | ------------- | -------------|
-{{#vars}}|**{{name}}** | {{#isEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isEnum}}{{^isEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
+{{#vars}}|**{{name}}** | {{#isInnerEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isInnerEnum}}{{^isInnerEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isInnerEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
 {{/vars}}
-{{#vars}}{{#isEnum}}
+{{#vars}}{{#isInnerEnum}}
 
 
 ## Enum: {{datatypeWithEnum}}
 
 | Name | Value |
 |---- | -----|{{#allowableValues}}{{#enumVars}}
 | {{name}} | {{value}} |{{/enumVars}}{{/allowableValues}}
-{{/isEnum}}{{/vars}}
+{{/isInnerEnum}}{{/vars}}
 {{#vendorExtensions.x-implements.0}}
 
 ## Implemented Interfaces

modules/openapi-generator/src/main/resources/java-helidon/server/libraries/mp/pojo_doc.mustache

@@ -8,17 +8,17 @@
 
 | Name | Type | Description | Notes |
 |------------ | ------------- | ------------- | -------------|
-{{#vars}}|**{{name}}** | {{#isEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isEnum}}{{^isEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
+{{#vars}}|**{{name}}** | {{#isInnerEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isInnerEnum}}{{^isInnerEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}**{{baseType}}{{#items}}<{{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}**Map<String, {{dataType}}>**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}**{{dataType}}**{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{baseType}}.md){{/isModel}}{{/isContainer}}{{/isInnerEnum}} | {{description}} | {{^required}} [optional]{{/required}}{{#isReadOnly}} [readonly]{{/isReadOnly}} |
 {{/vars}}
-{{#vars}}{{#isEnum}}
+{{#vars}}{{#isInnerEnum}}
 
 
 ## Enum: {{datatypeWithEnum}}
 
 | Name | Value |
 |---- | -----|{{#allowableValues}}{{#enumVars}}
 | {{name}} | {{value}} |{{/enumVars}}{{/allowableValues}}
-{{/isEnum}}{{/vars}}
+{{/isInnerEnum}}{{/vars}}
 {{#vendorExtensions.x-implements.0}}
 
 ## Implemented Interfaces

modules/openapi-generator/src/main/resources/java-micronaut/common/doc/pojo_doc.mustache

@@ -11,11 +11,11 @@ The class is defined in **[{{classname}}.java](../../{{{modelFolder}}}/{{classna
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-{{#vars}}**{{name}}** | {{#isEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isEnum}}{{^isEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}`{{baseType}}{{#items}}<{{dataType}}>`{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{#baseType}}{{baseType}}{{/baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}`Map<String, {{dataType}}>`{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{#baseType}}{{baseType}}{{/baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}`{{dataType}}`{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{#baseType}}{{baseType}}{{/baseType}}.md){{/isModel}}{{/isContainer}}{{/isEnum}} | {{description}} | {{^required}} [optional property]{{/required}}{{#isReadOnly}} [readonly property]{{/isReadOnly}}
+{{#vars}}**{{name}}** | {{#isInnerEnum}}[**{{datatypeWithEnum}}**](#{{datatypeWithEnum}}){{/isInnerEnum}}{{^isInnerEnum}}{{#isContainer}}{{#isArray}}{{#items}}{{#isModel}}[{{/isModel}}{{/items}}`{{baseType}}{{#items}}<{{dataType}}>`{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{#baseType}}{{baseType}}{{/baseType}}.md){{/isModel}}{{/items}}{{/isArray}}{{#isMap}}{{#items}}{{#isModel}}[{{/isModel}}`Map<String, {{dataType}}>`{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{#baseType}}{{baseType}}{{/baseType}}.md){{/isModel}}{{/items}}{{/isMap}}{{/isContainer}}{{^isContainer}}{{#isModel}}[{{/isModel}}`{{dataType}}`{{#isModel}}]({{^baseType}}{{dataType}}{{/baseType}}{{#baseType}}{{baseType}}{{/baseType}}.md){{/isModel}}{{/isContainer}}{{/isInnerEnum}} | {{description}} | {{^required}} [optional property]{{/required}}{{#isReadOnly}} [readonly property]{{/isReadOnly}}
 {{/vars}}
 {{#vars}}
 
-    {{#isEnum}}
+    {{#isInnerEnum}}
 ## {{datatypeWithEnum}}
 
 Name | Value
@@ -25,7 +25,7 @@ Name | Value
 {{name}} | `{{{value}}}`
         {{/enumVars}}
     {{/allowableValues}}
-    {{/isEnum}}
+    {{/isInnerEnum}}
 {{/vars}}
 {{#vendorExtensions.x-implements.0}}
 

modules/openapi-generator/src/main/resources/java-micronaut/common/model/oneof_interface.mustache

@@ -3,6 +3,13 @@
 {{/additionalOneOfTypeAnnotations}}
 {{>common/generatedAnnotation}}{{>common/model/typeInfoAnnotation}}{{>common/model/xmlAnnotation}}
 public interface {{classname}} {{#vendorExtensions.x-implements}}{{#-first}}extends {{{.}}}{{/-first}}{{^-first}}, {{{.}}}{{/-first}}{{/vendorExtensions.x-implements}} {
+    {{#vars}}
+    {{#isEnum}}
+    {{#isDiscriminator}}
+{{>common/model/modelInnerEnum}}
+    {{/isDiscriminator}}
+    {{/isEnum}}
+    {{/vars}}
     {{#discriminator}}
     public {{propertyType}} {{propertyGetter}}();
     {{/discriminator}}

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

@@ -2481,6 +2481,41 @@ public void testOneOfInterfaceGeneration() throws Exception {
         assertFileNotContains(Paths.get(modelDir + "DogRequest.java"), "@JsonTypeName(\"DogRequest\")");
     }
 
+    @Test
+    public void testOneOfInterfaceInlineDiscriminatorEnum() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/bugs/issue_25398.yaml", null, new ParseOptions()).getOpenAPI();
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.setUseOneOfInterfaces(true);
+        new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen)).generate();
+
+        Path pet = output.toPath().resolve("src/gen/java/org/openapitools/model/Pet.java");
+        assertFileContains(pet, "public enum PetTypeEnum {", "import com.fasterxml.jackson.annotation.*;",
+                "PetTypeEnum getPetType();");
+        Path dog = output.toPath().resolve("src/gen/java/org/openapitools/model/Dog.java");
+        assertFileContains(dog, "implements Pet", "public PetTypeEnum getPetType()");
+        assertFileNotContains(dog, "public enum PetTypeEnum {");
+    }
+
+    @Test
+    public void testPropertyLevelOneOfInterfaceInlineDiscriminatorEnum() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/bugs/issue_25398_property_level.yaml", null, new ParseOptions()).getOpenAPI();
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.setUseOneOfInterfaces(true);
+        new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen)).generate();
+
+        Path ownerPet = output.toPath().resolve("src/gen/java/org/openapitools/model/OwnerPet.java");
+        assertFileContains(ownerPet, "public enum PetTypeEnum {", "PetTypeEnum getPetType();");
+        Path dog = output.toPath().resolve("src/gen/java/org/openapitools/model/Dog.java");
+        assertFileContains(dog, "implements OwnerPet", "public PetTypeEnum getPetType()");
+        assertFileNotContains(dog, "public enum PetTypeEnum {");
+    }
+
     @Test
     public void generatesEmailAnnotationWhenBeanValidationEnabled() throws IOException {
         File output = Files.createTempDirectory("test").toFile().getCanonicalFile();

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

@@ -2565,6 +2565,17 @@ void testOneOfWithEnumDiscriminator() throws IOException {
         );
     }
 
+    @Test
+    public void testOneOfInterfaceDeclaresInlineDiscriminatorEnum() throws IOException {
+        Map<String, File> files = generateFromContract("src/test/resources/bugs/issue_25398.yaml", SPRING_BOOT);
+
+        assertThat(files.get("Pet.java").toPath()).content()
+                .contains("public enum PetTypeEnum {", "public PetTypeEnum getPetType();");
+        assertThat(files.get("Dog.java").toPath()).content()
+                .contains("private PetTypeEnum petType;")
+                .doesNotContain("enum PetTypeEnum");
+    }
+
     @Test
     public void testTypeMappings() {
         final SpringCodegen codegen = new SpringCodegen();

modules/openapi-generator/src/test/resources/bugs/issue_25398.yaml

@@ -0,0 +1,35 @@
+openapi: 3.0.1
+info:
+  title: oneOf interface with an inline enum discriminator
+  version: 0.0.1
+paths: {}
+components:
+  schemas:
+    Pet:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+          enum:
+            - dog
+            - cat
+      oneOf:
+        - $ref: '#/components/schemas/Dog'
+        - $ref: '#/components/schemas/Cat'
+      discriminator:
+        propertyName: petType
+        mapping:
+          dog: Dog
+          cat: Cat
+    Dog:
+      type: object
+      properties:
+        breed:
+          type: string
+    Cat:
+      type: object
+      properties:
+        declawed:
+          type: boolean