[BUG] [ExampleGenerator] Generated examples from Composed schema types are null (allOf, oneOf, anyOf...)

[acouvreur]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating an example for a model defined as a composite schema, such as:

Current (undesired) behavior:

Consider the following schema:

components:
  schemas:
    ExampleSchema:
      type: object
      properties:
        example_schema_property:
          type: string
          example: example schema property value
    ExampleComposedSchema:
      type: object
      allOf:
        - $ref: '#/components/schemas/ExampleSchema'
        - type: object
          properties:
            example_schema_property_composed:
              type: string
              example: example schema property value composed

I'd expect the generated example to look like:

{
  "example_schema_property": "example schema property value",
  "example_schema_property_composed": "example schema property value composed"
}

However, it currently generates the following:

null

Why is this behavior happening?

It's because only examples and properties are being supported right now:

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

Lines 349 to 363 in a5d3fb4

	if (schema.getExample() != null) {
	LOGGER.debug("Using example from spec: {}", schema.getExample());
	return schema.getExample();
	} else if (schema.getProperties() != null) {
	LOGGER.debug("Creating example from model values");
	for (Object propertyName : schema.getProperties().keySet()) {
	Schema property = (Schema) schema.getProperties().get(propertyName.toString());
	values.put(propertyName.toString(), resolvePropertyToExample(propertyName.toString(), mediaType, property, processedModels));
	}
	schema.setExample(values);
	return schema.getExample();
	} else {
	// TODO log an error message as the model does not have any properties
	return null;
	}

The message

// TODO log an error message as the model does not have any properties 

is wrong because composed schema may exist.

openapi-generator version

master a5d3fb4

OpenAPI declaration file content or url

openapi: 3.0.2
info:
  version: 1.0.0
  title: OpenAPI Petstore
  license:
    name: Apache-2.0
paths:
  /generate_from_response_schema_with_composed_model:
    get:
      operationId: generateFromResponseSchemaWithComposedModel
      responses:
        '200':
          description: successful operation
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ExampleComposedSchema'
components:
  schemas:
    ExampleSchema:
      type: object
      properties:
        example_schema_property:
          type: string
          example: example schema property value
    ExampleComposedSchema:
      type: object
      allOf:
        - $ref: '#/components/schemas/ExampleSchema'
        - type: object
          properties:
            example_schema_property_composed:
              type: string
              example: example schema property value composed

Generation Details

Run ExampleGeneratorTest.java

Steps to reproduce

Apply to following patch:

Subject: [PATCH] Add failing test case to ExampleGenerator for composed schema
---
Index: modules/openapi-generator/src/test/resources/3_0/example_generator_test.yaml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/modules/openapi-generator/src/test/resources/3_0/example_generator_test.yaml b/modules/openapi-generator/src/test/resources/3_0/example_generator_test.yaml
--- a/modules/openapi-generator/src/test/resources/3_0/example_generator_test.yaml	(revision a5d3fb4f601e4bced19f39cb6d82799a71531282)
+++ b/modules/openapi-generator/src/test/resources/3_0/example_generator_test.yaml	(date 1703875535793)
@@ -53,7 +53,7 @@
                   example: primitive types example value
   /generate_from_response_schema_with_model:
     get:
-      operationId: generateFromResponseSchemaWithArrayOfPrimitiveTypes
+      operationId: generateFromResponseSchemaWithModel
       responses:
         '200':
           description: successful operation
@@ -61,6 +61,16 @@
             application/json:
               schema:
                 $ref: '#/components/schemas/ExampleSchema'
+  /generate_from_response_schema_with_composed_model:
+    get:
+      operationId: generateFromResponseSchemaWithComposedModel
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ExampleComposedSchema'
 components:
   schemas:
     StringSchema:
@@ -72,3 +82,12 @@
         example_schema_property:
           type: string
           example: example schema property value
+    ExampleComposedSchema:
+      type: object
+      allOf:
+        - $ref: '#/components/schemas/ExampleSchema'
+        - type: object
+          properties:
+            example_schema_property_composed:
+              type: string
+              example: example schema property value composed
Index: modules/openapi-generator/src/test/java/org/openapitools/codegen/ExampleGeneratorTest.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ExampleGeneratorTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ExampleGeneratorTest.java
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ExampleGeneratorTest.java	(revision a5d3fb4f601e4bced19f39cb6d82799a71531282)
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ExampleGeneratorTest.java	(date 1703875564840)
@@ -146,6 +146,35 @@
                 mediaTypeKeys
         );
 
+        assertEquals(1, examples.size());
+        assertEquals("application/json", examples.get(0).get("contentType"));
+        assertEquals(String.format(Locale.ROOT, "{%n  \"example_schema_property\" : \"example schema property value\"%n}"), examples.get(0).get("example"));
+        assertEquals("200", examples.get(0).get("statusCode"));
+    }
+
+    @Test
+    public void generateFromResponseSchemaWithComposedModel() {
+        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_composed_model")
+                        .getGet()
+                        .getResponses()
+                        .get("200")
+                        .getContent()
+                        .get("application/json")
+                        .getSchema(),
+                mediaTypeKeys
+        );
+
         assertEquals(1, examples.size());
         assertEquals("application/json", examples.get(0).get("contentType"));
         assertEquals(String.format(Locale.ROOT, "{%n  \"example_schema_property\" : \"example schema property value\"%n}"), examples.get(0).get("example"));

Related issues/PRs

Suggest a fix

Will open a PR soon