Combination of allOf and discriminator gives false warnings

[fehguy]

If you create a schema with definitions that include a discriminator, you will get a false warning that some models are not in use. In fact, they may be in use indirectly.

For example:

  Animal:
    type: object
    discriminator: petType
    properties:
      commonName:
        type: string
  Cat:
    allOf:
      - $ref: '#/definitions/Animal'
      - type: object
        properties:
          isFurry:
            type: boolean
            default: false

Will give a warning like such:

It can be difficult to decide what may be referenced by a discriminator, I believe we can encapsulate it in a fairly simple rule:

• If a schema contains the discriminator field, AND that schema is referenced in an allOf construct, AND neither models are inline schemas, we should ignore any warnings that the allOf model is unused.

[saharj]

Neither in online swagger, nor on master I could reproduce this. Here is my swagger:

swagger: '2.0'
info:
  version: 0.0.0
  title: Simple API
paths:
  /:
    get:
      responses:
        200:
          description: OK
          schema: 
            $ref: "#/definitions/Cat"
definitions:
  Animal:
    type: object
    discriminator: petType
    properties:
      commonName:
        type: string
  Cat:
    allOf:
      - $ref: '#/definitions/Animal'
      - type: object
        properties:
          isFurry:
            type: boolean
            default: false

You probably didn't use the schema.

[fehguy]

Try changing the response type to Animal, which is a common pattern:

swagger: '2.0'
info:
  version: 0.0.0
  title: Simple API
paths:
  /:
    get:
      responses:
        200:
          description: OK
          schema: 
            $ref: "#/definitions/Animal"
definitions:
  Animal:
    type: object
    discriminator: petType
    properties:
      commonName:
        type: string
  Cat:
    allOf:
      - $ref: '#/definitions/Animal'
      - type: object
        properties:
          isFurry:
            type: boolean
            default: false        

This will define the basic response as an Animal and concrete implementations by the discriminator field.

[saharj]

Here is my understanding about this:
Cat is using Animal, the schema is referring to Animal, too. So there is nothing that uses Cat (Animal doesn't use Cat). In this case, the warning is valid.
Am I missing something?

[fehguy]

It is a tiny bit different. Think of Animal as the generic response for the operation--it returns some kind of animal but you don't know what.

When the discriminator value is set to Cat in the response, the client knows that the response type is actually a Cat rather than generic Animal.

Since we don't actually know what type could be in the response (it may refer to Alien) of which there is no definition in the schema, we look at the allOf references. Because Cat is referencing Animal in an allOf construct, we know that it's a possible response type, and therefore it is "in use".

Does that make sense?

[dirisiopablo]

Hi @fehguy, have you found a workaround to deal with this issue? I'm facing that warning right now and can't make it disappear.

Thanks in advance. Pablo.

[fehguy]

No, as of now there is no work around other than ignoring the warning

[dirisiopablo]

Well, I'll do that. Thanks for reply.