Add logic and test case to avoid stackOverflow exception for circular allOf

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

@@ -406,14 +406,27 @@ private void traverseSchemaProperties(String mediaType, Schema schema, Set<Strin
      */
     private void resolveAllOfSchemaProperties(String mediaType, Schema schema, Set<String> processedModels, Map<String, Object> values) {
         List<Schema> interfaces = schema.getAllOf();
+        if (interfaces == null) {
+            return;
+        }
+
         for (Schema composed : interfaces) {
-            traverseSchemaProperties(mediaType, composed, processedModels, values);
             if (composed.get$ref() != null) {
                 String ref = ModelUtils.getSimpleRef(composed.get$ref());
+
+                if (processedModels.contains(ref)) {
+                    LOGGER.warn("Circular reference detected in allOf for $ref: {}. Skipping.", ref);
+                    continue;
+                }
+
                 Schema resolved = ModelUtils.getSchema(openAPI, ref);
                 if (resolved != null) {
+                    processedModels.add(ref);
                     traverseSchemaProperties(mediaType, resolved, processedModels, values);
+                    processedModels.remove(ref);
                 }
+            } else {
+                traverseSchemaProperties(mediaType, composed, processedModels, values);
             }
         }
     }

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

@@ -8,7 +8,6 @@
 
 import java.util.*;
 
-import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import static org.testng.AssertJUnit.assertEquals;
@@ -249,6 +248,68 @@ public void generateFromResponseSchemaWithAllOfComposedModel() throws Exception{
         assertEquals("200", examples.get(0).get("statusCode"));
     }
 
+    @Test
+    public void generateFromResponseSchemaWithAllOfCircularSchema() throws Exception{
+        OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/example_generator_test.yaml");
+
+        new InlineModelResolver().flatten(openAPI);
+
+        ExampleGenerator exampleGenerator = new ExampleGenerator(openAPI.getComponents().getSchemas(), openAPI);
+        Set<String> mediaTypeKeys = new TreeSet<>();
+        mediaTypeKeys.add("application/json");
+        List<Map<String, String>> examples = exampleGenerator.generateFromResponseSchema(
+                "200",
+                openAPI
+                        .getPaths()
+                        .get("/generate_from_response_schema_with_allOf_circular_model")
+                        .getGet()
+                        .getResponses()
+                        .get("200")
+                        .getContent()
+                        .get("application/json")
+                        .getSchema(),
+                mediaTypeKeys
+        );
+
+        ObjectMapper mapper = new ObjectMapper();
+
+        assertEquals(1, examples.size());
+        assertEquals("application/json", examples.get(0).get("contentType"));
+        assertEquals(mapper.readTree(String.format(Locale.ROOT, "{%n  \"example_schema_property_alloff_circular\" : \"example schema property allOff circular\"%n}")), mapper.readTree(examples.get(0).get("example")));
+        assertEquals("200", examples.get(0).get("statusCode"));
+    }
+
+    @Test
+    public void generateFromResponseSchemaWithAllOfSiblingSchema() throws Exception{
+        OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/example_generator_test.yaml");
+
+        new InlineModelResolver().flatten(openAPI);
+
+        ExampleGenerator exampleGenerator = new ExampleGenerator(openAPI.getComponents().getSchemas(), openAPI);
+        Set<String> mediaTypeKeys = new TreeSet<>();
+        mediaTypeKeys.add("application/json");
+        List<Map<String, String>> examples = exampleGenerator.generateFromResponseSchema(
+                "200",
+                openAPI
+                        .getPaths()
+                        .get("/generate_from_response_schema_with_allOf_sibling_model")
+                        .getGet()
+                        .getResponses()
+                        .get("200")
+                        .getContent()
+                        .get("application/json")
+                        .getSchema(),
+                mediaTypeKeys
+        );
+
+        ObjectMapper mapper = new ObjectMapper();
+
+        assertEquals(1, examples.size());
+        assertEquals("application/json", examples.get(0).get("contentType"));
+        assertEquals(mapper.readTree(String.format(Locale.ROOT, "{%n \"base\":{\"example_schema_property\":\"example schema property value\",\"example_schema_property_composed\":\"example schema property value composed\"}, \"sibling\":{\"example_schema_property\":\"example schema property value\",\"example_schema_property_composed\":\"example schema property value composed\"} %n}")), mapper.readTree(examples.get(0).get("example")));
+        assertEquals("200", examples.get(0).get("statusCode"));
+    }
+
     @Test
     public void generateFromResponseSchemaWithAllOfChildComposedModel() throws Exception {
         OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/example_generator_test.yaml");

modules/openapi-generator/src/test/resources/3_0/example_generator_test.yaml

@@ -101,6 +101,26 @@ paths:
             application/json:
               schema:
                 $ref: '#/components/schemas/ExampleAllOfParentSchema'
+  /generate_from_response_schema_with_allOf_circular_model:
+    get:
+      operationId: generateFromResponseSchemaWithAllOfCircularModel
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ExampleAllOfCircularSchema'
+  /generate_from_response_schema_with_allOf_sibling_model:
+    get:
+      operationId: generateFromResponseSchemaWithAllOfSiblingModel
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ExampleAllOfSiblingContainerSchema'
   /generate_from_response_schema_with_anyOf_composed_model:
     get:
       operationId: generateFromResponseSchemaWithAnyOfModel
@@ -151,6 +171,15 @@ components:
             example_schema_property_composed:
               type: string
               example: example schema property value composed
+    ExampleAllOfSiblingSchema:
+      type: object
+      allOf:
+        - $ref: '#/components/schemas/ExampleSchema'
+        - type: object
+          properties:
+            example_schema_property_composed:
+              type: string
+              example: example schema property value composed
     ExampleAllOfParentSchema:
       type: object
       allOf:
@@ -160,6 +189,22 @@ components:
             example_schema_property_composed_parent:
               type: string
               example: example schema property value composed parent
+    ExampleAllOfCircularSchema:
+      type: object
+      allOf:
+        - $ref: '#/components/schemas/ExampleAllOfCircularSchema'
+        - type: object
+          properties:
+            example_schema_property_alloff_circular:
+              type: string
+              example: example schema property allOff circular
+    ExampleAllOfSiblingContainerSchema:
+      type: object
+      properties:
+        base:
+          $ref: '#/components/schemas/ExampleAllOfSchema'
+        sibling:
+          $ref: '#/components/schemas/ExampleAllOfSiblingSchema'
     ExampleAnyOfSchema:
       type: object
       anyOf: