fix ref sibiling using allOf in normalizer

Author: wing328

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

@@ -696,6 +696,11 @@ protected boolean isSelfReference(String name, Schema subSchema) {
      * @return Schema
      */
     public Schema normalizeSchema(Schema schema, Set<Schema> visitedSchemas) {
+        // normalize reference schema
+        if (StringUtils.isNotEmpty(schema.get$ref())) {
+            normalizeReferenceSchema(schema);
+        }
+
         if (skipNormalization(schema, visitedSchemas)) {
             return schema;
         }
@@ -763,6 +768,30 @@ public Schema normalizeSchema(Schema schema, Set<Schema> visitedSchemas) {
         return schema;
     }
 
+    /**
+     * Normalize reference schema with allOf to support sibling properties
+     *
+     * @param schema         Schema
+     */
+    protected void normalizeReferenceSchema(Schema schema) {
+        if (schema.getTitle() != null || schema.getDescription() != null
+                || schema.getNullable() != null || schema.getDefault() != null || schema.getDeprecated() != null
+                || schema.getMaximum() != null || schema.getMinimum() != null
+                || schema.getExclusiveMaximum() != null || schema.getExclusiveMinimum() != null
+                || schema.getMaxItems() != null || schema.getMinItems() != null
+                || schema.getMaxProperties() != null || schema.getMinProperties() != null
+                || schema.getMaxLength() != null || schema.getMinLength() != null
+                || schema.getWriteOnly() != null || schema.getReadOnly() != null
+                || schema.getExample() != null || (schema.getExamples() != null && !schema.getExamples().isEmpty())
+                || schema.getMultipleOf() != null || schema.getPattern() != null
+                || (schema.getExtensions() != null && !schema.getExtensions().isEmpty())
+        ) {
+            // create allOf with a $ref schema
+            schema.addAllOfItem(new Schema<>().$ref(schema.get$ref()));
+            // clear $ref in original schema
+            schema.set$ref(null);
+        }
+    }
 
     /**
      * Check if normalization is needed.

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

@@ -910,7 +910,10 @@ public void testOpenAPINormalizerSimplifyOneOfAnyOf31SpecForIssue18184() {
 
         Schema schema2 = openAPI.getComponents().getSchemas().get("Item");
         assertEquals(((Schema) schema2.getProperties().get("my_enum")).getAnyOf(), null);
-        assertEquals(((Schema) schema2.getProperties().get("my_enum")).get$ref(), "#/components/schemas/MyEnum");
+        assertEquals(((Schema) schema2.getProperties().get("my_enum")).getAllOf().size(), 1);
+        assertEquals(((Schema) schema2.getProperties().get("my_enum")).getNullable(), true);
+        assertEquals(((Schema) schema2.getProperties().get("my_enum")).get$ref(), null);
+        assertEquals(((Schema) ((Schema) schema2.getProperties().get("my_enum")).getAllOf().get(0)).get$ref(), "#/components/schemas/MyEnum");
     }
 
     @Test
@@ -1104,7 +1107,10 @@ public void testOpenAPINormalizerSimplifyOneOfAnyOf31Spec() {
         Schema schema18 = openAPI.getComponents().getSchemas().get("OneOfNullAndRef3");
         // original oneOf removed and simplified to just $ref (oneOf sub-schema) instead
         assertEquals(schema18.getOneOf(), null);
-        assertEquals(schema18.get$ref(), "#/components/schemas/Parent");
+        assertEquals(schema18.get$ref(), null);
+        assertEquals(schema18.getNullable(), true);
+        assertEquals(((Schema) schema18.getAllOf().get(0)).get$ref(), "#/components/schemas/Parent");
+
 
         Schema schema20 = openAPI.getComponents().getSchemas().get("ParentWithOneOfProperty");
         assertEquals(((Schema) schema20.getProperties().get("number")).get$ref(), "#/components/schemas/Number");
@@ -1184,6 +1190,24 @@ public void testOpenAPINormalizerProcessingAllOfSchema31Spec() {
         assertEquals(((Schema) schema2.getProperties().get("property2")).getAllOf(), null);
     }
 
+    @Test
+    public void testOpenAPINormalizerNormalizeReferenceSchema() {
+        // to test array schema processing in 3.1 spec
+        OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_1/unsupported_schema_test.yaml");
+
+        Schema schema = openAPI.getComponents().getSchemas().get("Dummy");
+        assertEquals(((Schema) schema.getProperties().get("property3")).get$ref(), "#/components/schemas/RefSchema");
+
+        Map<String, String> inputRules = Map.of("NORMALIZE_31SPEC", "true");
+        OpenAPINormalizer openAPINormalizer = new OpenAPINormalizer(openAPI, inputRules);
+        openAPINormalizer.normalize();
+
+        Schema schema2 = openAPI.getComponents().getSchemas().get("Dummy");
+        assertEquals(((Schema) schema2.getProperties().get("property3")).getAllOf().size(), 1);
+        assertEquals(((Schema) schema2.getProperties().get("property3")).getDescription(), "Override description in $ref schema");
+        assertEquals(((Schema) ((Schema) schema2.getProperties().get("property3")).getAllOf().get(0)).get$ref(), "#/components/schemas/RefSchema");
+    }
+
     @Test
     public void testOpenAPINormalizerComponentsResponses31Spec() {
         OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_1/common-parameters.yaml");

modules/openapi-generator/src/test/resources/3_1/unsupported_schema_test.yaml

@@ -24,6 +24,11 @@ paths:
                 $ref: "#/components/schemas/Dummy"
 components:
   schemas:
+    RefSchema:
+      description: reference schema
+      properties:
+        id:
+          type: string
     Dummy:
       type: object
       properties:
@@ -61,4 +66,7 @@ components:
                 enum:
                   - FIRST
                   - SECOND
-                  - THIRD
+                  - THIRD
+        property3:
+          $ref: "#/components/schemas/RefSchema"
+          description: Override description in $ref schema