Empty schema for responses

[tcrespog]

Expected Behavior

The generated schema field shouldn't be empty.

Actual Behaviour

Given the following controller method:

    @Post("/pet")
    @Operation(
            operationId = 'CreatePet',
            summary = 'Create a pet',
            requestBody = @RequestBody(description = 'Pet create request', content = @Content(schema = @Schema(implementation = CreatePetRequest))),
            responses = [
                    @ApiResponse(responseCode = '200', description = 'OK', content = @Content(schema = @Schema(implementation = CreatePetResponse))),
                    @ApiResponse(responseCode = '400', description = 'Bad request', content = @Content(schema = @Schema(implementation = ErrorResponse))),
                    @ApiResponse(responseCode = '403', description = 'Operation not allowed'),
                    @ApiResponse(responseCode = '409', description = 'Duplicated element', content = @Content(schema = @Schema(implementation = ErrorResponse)))
            ]
    )
    HttpResponse<CreatePetResponse> createPet(@Body CreatePetRequest body) {
        def respBody = new CreatePetResponse(pet: body.pet)

        return HttpResponse.ok(respBody)
    }

The generated specs contain empty schemas for responses:

openapi: 3.0.1
info:
  title: mn-openapi-empty-schema
  version: "0.0"
paths:
  /pet:
    post:
      summary: Create a pet
      operationId: CreatePet
      requestBody:
        description: Pet create request
        content:
          schema: {} # <----- empty schema here too, but the block below looks alright
          application/json:
            schema:
              $ref: '#/components/schemas/CreatePetRequest'
        required: true
      responses:
        "200":
          description: OK
          content:
            schema: {} # <---- empty schema for all responses
        "400":
          description: Bad request
          content:
            schema: {}
        "403":
          description: Operation not allowed
        "409":
          description: Duplicated element
          content:
            schema: {}
components:
  schemas:
    CreatePetRequest:
      type: object
      properties:
        pet:
          $ref: '#/components/schemas/Pet'
    Pet:
      type: object
      properties:
        name:
          type: string

The same method in Micronaut 3.x generates something such as the following:

      responses:
        "200":
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CreatePetResponse'

Steps To Reproduce

1. Download the sample project.
2. Run ./gradlew compileGroovy
3. In the generated specs are generated, the schema for responses is empty.

Environment Information

• Micronaut + Groovy (and Micronaut OpenAPI 6.5.1).
• Ubuntu 22.04.
• Java 17.

Example Application

https://github.com/tcrespog/mn-openapi-empty-schema

Version

4.2.3