[BUG] Example values are not generated for enum types referenced with $ref

Description

openapi-generator only produces example schemas/responses for enum types when they are inlined in the response type. When an enum is $referenced, no example value is produced. Because this happens with both openapi and spring generators, I assume this is a core bug and not specific to either generator.

With the declaration file below, I get

• "Specification" : { "example" : {"bar" : "BAR_A"} } for openapi rather than the expected "Specification" : { "example" : {"foo" : "FOO_A", "bar" : "BAR_A"} } and
• setExampleResponse(request, "application/json", "{ \"bar\" : \"BAR_A\"}") for Spring rather than the expected setExampleResponse(request, "application/json", "{ \"foo\": \"FOO_A\", \"bar\" : \"BAR_A\"}").

openapi-generator version

Problem seen at least in 4.0.3, 4.1.3, latest 4.2.0-SNAPSHOT and 5.0.0-SNAPSHOT.

OpenAPI declaration file content or url

openapi: "3.0.0"
info:
  version: 0.0.1
  title: Enum example

components:
  schemas:
    Foo:
      type: string
      enum:
        - FOO_A
        - FOO_B
    Specification:
      type: object
      properties:
        foo:
          $ref: '#/components/schemas/Foo'
        bar:
          type: string
          enum:
            - BAR_A
            - BAR_B
      required:
        - foo
        - bar

paths:
  /hello:
    get:
      responses:
        200:
          description: Success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Specification'

Command line used for generation

java -jar openapi-generator-cli-4.2.0-20191028.135625-129.jar generate -i api.yaml -g openapi -o oa-420/ java -jar openapi-generator-cli-4.2.0-20191028.135625-129.jar generate -i api.yaml -g spring -o spring-420/

Steps to reproduce

Generate an Openapi JSON file or a Spring application with the above command lines and check $.components.schemas.Specification.example and HelloApi::helloGet(), respectively

Related issues/PRs

Could not find anything related to examples for enums; in:title enum example returned 0 matches.

[lwlee2608]

I am able to resolve it by replacing this line https://github.com/OpenAPITools/openapi-generator/blob/a2b37d67c05a9e09a047d0c5d20652326fe3d2fa/modules/openapi-generator/src/main/java/org/openapitools/codegen/examples/ExampleGenerator.java#L354

from return null; to return resolvePropertyToExample(name, mediaType, schema, processedModels);

However, I’m not sure if it is a correct fix.

[Johnlon]

This is really bugging me as I want to rejuvenate the flask generator and fix a load of bugs and gaps in enum handling but this one probem has me stuck. I cannot figure out how to get the generated code to contain a legal example value or legal enum value of any kind. And I hate that.

Any way folk …

What’s the required behaviour here?

• Look for a “example” field on the request paramter and use that? Or drill down the to the referred enum type and …
• Pick any one of the valid enum values and use it as the value in the test code?
• or look for a “example” field in the enum and use that?
• or look for a “default” field in the enum and use that?

(PS @lwlee2608 that change above didn’t work for me)

The python code I get generated in the controller test is just wrong. The substituted example value “openapi_server.OuterEnumInteger()” can’t even compile. Even “openapi_server.models.OuterEnumInteger()” would be wrong as this is imported. Using just “OuterEnumInteger()” compiles at least. However, even then we get a runtime error because “OuterEnumInteger()” is not a valid value for the enum which is actually an int inmy case.

        body = 'body_example'
        query_string = [('enum_query_int', openapi_server.OuterEnumInteger())]
        headers = {
            'Accept': '*/*',

 /enum-post-json:
    post:
      description: Test serialization of enum properties with examples
      operationId: enum_post_json
      responses:
        '200':
          description: Output enum corncopia
          content:
            '*/*':
              schema:
                type: string
      parameters:
      - description: Query outer enum parameter
        in: query
        name: enum_query_int
        required: false
        # TODO Code gen doesn't pick this example up nor the one in the referred type unfortunately - and the generated controller test is not valid code
        # https://github.com/OpenAPITools/openapi-generator/issues/4300
        example: 1
        schema:
          $ref: '#/components/schemas/OuterEnumInteger'
      requestBody:
        required: true
        content:
          application/json:
            schema:
                type: string

What the param type is ...

    OuterEnumInteger:
      type: integer
      enum:
      - 0
      - 1
      - 2
      example: 2