Swagger: Additional properties not allowed: allOf

Question

I'm trying to figure out this swagger API inheritance stuff by using allOf. This is my swagger yaml file.

swagger: '2.0'
info:
  title: Test API
  version: '1'
basePath: /api/v1
schemes:
  - https
produces:
  - application/json

paths:
  /users:
    get:
      summary: Collection of users
      tags:
        - users
      responses:
        200:
          description: A list of Users
          schema:
            $ref: "#/definitions/Users"        
        500:
          $ref: "#/responses/BadRequest"

definitions:
  User:
    required:
      - username
    properties:
      firstName:
        type: string
      lastName:
        type: string
      username:
        type: string
  Users:
    type: array
    items:
      $ref: "#/definitions/User"

responses:
  NonSuccess:
    description: Generic response for all non-success responses
    schema:
      type: object
      required:
        - code
        - message
      properties:
        code:
          type: integer
          description: The success code, 0 or -1.
        message:
          type: string
          description: The description message for this success code
        errors:
          type: array
          description: A map of errors within the request. Keyed by the parameter name and the values are the error details

  BadRequest:
    description: Invalid request parameters
    allOf:
      - $ref: "#/responses/NonSuccess"

When I paste this into the online editor, I get the following errors that I'm having a real hard time trying to figure out.

✖ Swagger Error
Additional properties not allowed: allOf
Jump to line 60

✖ Swagger Error
Not a valid response definition
Jump to line 22

The main problem seems to be Additional properties not allowed: allOf and I'm can't seem to figure out what I'm doing wrong in this case. I was trying to declare a basic non-success response so that all non-200 responses will inherit so that the API will have a very standard looking non-success response. I was under the impression I could do this with allOf and then add or overwrite the fields from that response. What exactly am I doing wrong?

Solution

The allOf tag can only be used on Schema objects. You can definitely use it on the Schema portion of the response, though. Here's an example of that.

swagger: '2.0'
info:
  title: Test API
  version: '1'
basePath: /api/v1
schemes:
  - https
produces:
  - application/json

paths:
  /users:
    get:
      summary: Collection of users
      tags:
        - users
      responses:
        200:
          description: A list of Users
          schema:
            $ref: "#/definitions/Users"        
        500:
          $ref: "#/responses/BadRequest"

definitions:
  User:
    required:
      - username
    properties:
      firstName:
        type: string
      lastName:
        type: string
      username:
        type: string
  Users:
    type: array
    items:
      $ref: "#/definitions/User"

  Response:
    type: object
    required:
      - code
      - message
    properties:
      code:
        type: integer
        description: The success code, 0 or -1.
      message:
        type: string
        description: The description message for this success code
      errors:
        type: array
        description: A map of errors within the request. Keyed by the parameter name and the values are the error details

  BadRequest:
    type: object
    required:
      - validationErrors
    properties:
      validationErrors:
        type: array
        items:
          type: string

responses:
  NonSuccess:
    description: Generic response for a non-success
    schema:
      $ref: "#/definitions/Response"

  BadRequest:
    description: Invalid request parameters
    schema:
      allOf:
        - $ref: "#/definitions/Response"
        - $ref: "#/definitions/BadRequest"

Comments

[SynackSA]

Yip, this is pretty much where I ended up.