Discriminator dropdown shown for all variants

I have a base schema Pet with a discriminant petType and some schemas Cat, Dog and Lizard that inherit from it. When I use the Pet schema in documentation, I get the dropdown for petType as expected with each of the different types, but when I use the Cat type I also get the same, despite petType: "Cat" being the only valid value for this.

These are the types I get (first Pet and then Cat):

For the second one, I'd expect something like this instead:

These are the files that I'm using for this test case:

openapi: 3.0.2
info:
  title: Test API
  version: playground
servers: []

paths:
  /pets:
    get:
      summary: "Get all pets"
      responses:
        200:
          description: ""
          content:
            application/json:
              schema:
                type: object
                properties:
                  items:
                    type: array
                    items:
                      $ref: "#/components/schemas/Pet"
  /cats:
    get:
      summary: "Get all cats"
      responses:
        200:
          description: ""
          content:
            application/json:
              schema:
                type: object
                properties:
                  items:
                    type: array
                    items:
                      $ref: "#/components/schemas/Cat"

components:
  schemas:
    Pet:
      type: object
      description: "Pet superclass"
      required:
        - petType
      properties:
        petType:
          type: string
          description: "Pet type"
      discriminator:
        propertyName: petType
    Cat:
      description: "Cat subclass"
      allOf:
        - $ref: "#/components/schemas/Pet"
        - type: object
          # all other properties specific to a `Cat`
          properties:
            name:
              description: "Name"
              type: string
    Dog:
      description: "Dog subclass"
      allOf:
        - $ref: "#/components/schemas/Pet"
        - type: object
          # all other properties specific to a `Dog`
          properties:
            bark:
              description: "Bark"
              type: string
    Lizard:
      description: "Lizard subclass"
      allOf:
        - $ref: "#/components/schemas/Pet"
        - type: object
          # all other properties specific to a `Lizard`
          properties:
            lovesRocks:
              description: "Loves rocks"
              type: boolean

[adamaltman]

I think you may have missed part of the definition.

Try this to get what you're looking for (I think):

openapi: 3.0.2
info:
  title: Test API
  version: playground
servers: []

paths:
  /pets:
    get:
      summary: "Get all pets"
      responses:
        200:
          description: ""
          content:
            application/json:
              schema:
                type: object
                properties:
                  items:
                    type: array
                    items:
                      $ref: "#/components/schemas/Pet"
  /cats:
    get:
      summary: "Get all cats"
      responses:
        200:
          description: ""
          content:
            application/json:
              schema:
                type: object
                properties:
                  items:
                    type: array
                    items:
                      $ref: "#/components/schemas/Cat"

components:
  schemas:
    Pet:
      type: object
      description: "Pet superclass"
      required:
        - petType
      properties:
        oneOf:
          - $ref: '#/components/schemas/Cat'
          - $ref: '#/components/schemas/Dog'
          - $ref: '#/components/schemas/Lizard'
      discriminator:
        propertyName: petType
        mapping:
          Cat: '#/components/schemas/Cat'
          Dog: '#/components/schemas/Dog'
          Lizard: '#/components/schemas/Lizard'
    Cat:
      description: "Cat subclass"
      allOf:
        - type: object
          properties:
            petType:
              type: string
              description: "Pet type"
              enum:
                - Cat
          # all other properties specific to a `Cat`
            name:
              description: "Name"
              type: string
    Dog:
      description: "Dog subclass"
      allOf:
        - type: object
          properties:
            petType:
              type: string
              description: "Pet type"
              enum:
                - Dog
          # all other properties specific to a `Dog`
            bark:
              description: "Bark"
              type: string
    Lizard:
      description: "Lizard subclass"
      allOf:
        - type: object
          properties:
            petType:
              type: string
              description: "Pet type"
              enum:
                - Lizard
          # all other properties specific to a `Lizard`
            lovesRocks:
              description: "Loves rocks"
              type: boolean

[ladcognite]

The pet schemas in the original post is the exact example from the OpenAPI discriminator documentation https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md#discriminator-object , so it should be a valid definition.

With the suggested alternative, the different pets have no common parent schema.
If we want to add a 'color' parameter to all pets, it either has to be duplicated across all the pets, or we'll have to introduce yet another pet superclass that the pets can include as an allOf.
While this should work, it's not a very clean solution.