Support multiple successful responses based on status code

[daniel-v]

Use case

Assume we are working with an API that returns a List<String> for the owner's pet names.

There are 2 successful branches here:

1. 200 - a body with appropriate content-length header and the list of pet name
2. 204 - No-Content which results in content-length: 0. The owner does not yet have any pets

Currently, if both 200 and 204 are specified and No-Content response returns with empty body, an exception will be thrown.

Error: Null check operator used on a null value

because the generated code uses ! operator on .data field of result.

What I'm looking for is the ability to be able to do something like this:

openapi: 3.0.4
info:
  title: Mini pets
  version: "1.0"
paths:
  /pets:
    get:
      summary: Gets the list of pets
      responses:
        200:
          description: List of pet names
          content:
            application/json:
              schema:
                type: array
                items:
                  type: string
        204:
          description: No pets yet

Proposal

In such situations, returning with a freezed union type would probably cover the usecase.