Do not remove schemas with only a default value form allOf schemas

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

@@ -2375,7 +2375,8 @@ public static boolean isMetadataOnlySchema(Schema schema) {
                 schema.getContains() != null ||
                 schema.get$dynamicAnchor() != null ||
                 schema.get$anchor() != null ||
-                schema.getContentSchema() != null;
+                schema.getContentSchema() != null ||
+                schema.getDefault() != null;
     }
 
 

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

@@ -1205,4 +1205,18 @@ public void doNotWrapSingleAllOfRefs() {
         assertNotNull(allOfRefWithDescriptionAndReadonly.getAllOf());
         assertEquals(numberRangeRef, ((Schema) allOfRefWithDescriptionAndReadonly.getAllOf().get(0)).get$ref());
     }
+
+    @Test
+    public void testAllOfEnumWithDefault() {
+        // The flattened spec should still have both allOf items in query parameter, to allow generators to generate the default value
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf-enum-default.yaml");
+        var parameters = openAPI
+                .getPaths()
+                .get("/person")
+                .getGet()
+                .getParameters();
+        assertEquals(1, parameters.size());
+        var parameter = parameters.get(0);
+        assertEquals(2, parameter.getSchema().getAllOf().size());
+    }
 }

modules/openapi-generator/src/test/resources/3_0/allOf-enum-default.yaml

@@ -0,0 +1,31 @@
+openapi: 3.0.1
+info:
+  version: 1.0.0
+  title: Example
+  license:
+    name: MIT
+servers:
+  - url: http://api.example.xyz/v1
+paths:
+  /person:
+    get:
+      parameters:
+        - name: enum
+          in: query
+          required: true
+          description: Enum value
+          schema:
+            allOf:
+              - $ref: '#/components/schemas/MyEnum'
+              - default: "One"
+      operationId: list
+      responses:
+        '200':
+          description: OK
+components:
+  schemas:
+    MyEnum:
+      type: string
+      enum:
+        - One
+        - Two