Sub-types not generated from go discriminated type

[zgramana]

Problem statement

Sub-types are not emitted for a discriminated type when using go annotations to generate an OpenAPI spec.

Annotated go

openapi.go

// From https://goswagger.io/use/spec/discriminated.html

// TeslaCar is a tesla car
//
// swagger:model
type TeslaCar interface {
	// The model of tesla car
	//
	// discriminator: true
	// swagger:name model
	Model() string

	// AutoPilot returns true when it supports autopilot
	// swagger:name autoPilot
	AutoPilot() bool
}

// The ModelS version of the tesla car
//
// swagger:model modelS
type ModelS struct {
	// swagger:allOf com.tesla.models.ModelS
	TeslaCar
	// The edition of this Model S
	Edition string `json:"edition"`
}

// The ModelX version of the tesla car
//
// swagger:model modelX
type ModelX struct {
	// swagger:allOf com.tesla.models.ModelX
	TeslaCar
	// The number of doors on this Model X
	Doors int32 `json:"doors"`
}

// Add a reference to tie TeslaCar into the type definitions hierarchy...

// swagger:response carResponse
type CarResponse struct {
	// in: body
	Body struct {
		Result  int
		Vehicle TeslaCar
	}
}

routes.go

...
	// swagger:route GET /car GetCar
	//
	// Gets a Tesla car
	//
	//   Produces:
	//   - application/json
	//
	//   Responses:
	//     200: carResponse
	router.Handle("/", makeCarHandler()).Methods("GET")
...

Generated Swagger Specification

basePath: /
consumes:
- application/json
definitions:
  TeslaCar:
    description: TeslaCar is a tesla car
    discriminator: model
    properties:
      autoPilot:
        description: AutoPilot returns true when it supports autopilot
        type: boolean
        x-go-name: AutoPilot
      model:
        description: The model of tesla car
        type: string
        x-go-name: Model
    type: object
    x-go-package: github.com/foo/bar
info:
  description: Package main Car API
  version: "1.0"
paths:
  /car:
    get:
      description: Gets a job document
      operationId: GetRoot
      produces:
      - application/json
      responses:
        "200":
          $ref: '#/responses/carResponse'
produces:
- application/json
responses:
  carResponse:
    schema:
      properties:
        Result:
          format: int64
          type: integer
        Vehicle:
          $ref: '#/definitions/TeslaCar'
      type: object
schemes:
- http
- https
swagger: "2.0"

Steps to reproduce

1. Create new go project with the above code.
2. Run swagger generate spec -o swagger.yaml

Note

Running the generate command with -m/--scan-models does force the subtypes to be emitted in the definitions array. However, this comes with the unfortunate side-effect of also generating a model for every swagger:response in definitions as well (see example below).

I say unfortunate since having to hand edit/cleanup the resulting spec breaks our CI/CD automation.

definitions:
  CarResponse:
    properties:
      Body:
        description: 'in: body'
        properties:
          Result:
            format: int64
            type: integer
          Vehicle:
            $ref: '#/definitions/TeslaCar'
        type: object
    type: object
    x-go-package: github.com/foo/bar
  TeslaCar:
    description: TeslaCar is a tesla car
    discriminator: model
    properties:
      autoPilot:
        description: AutoPilot returns true when it supports autopilot
        type: boolean
        x-go-name: AutoPilot
      model:
        description: The model of tesla car
        type: string
        x-go-name: Model
    type: object
    x-go-package: github.com/foo/bar
  modelS:
    allOf:
    - $ref: '#/definitions/TeslaCar'
    - properties:
        edition:
          description: The edition of this Model S
          type: string
          x-go-name: Edition
      type: object
    description: The ModelS version of the tesla car
    x-class: com.tesla.models.ModelS
    x-go-name: ModelS
    x-go-package: github.com/foo/bar
  modelX:
    allOf:
    - $ref: '#/definitions/TeslaCar'
    - properties:
        doors:
          description: The number of doors on this Model X
          format: int32
          type: integer
          x-go-name: Doors
      type: object
    description: The ModelX version of the tesla car
    x-class: com.tesla.models.ModelX
    x-go-name: ModelX
    x-go-package: github.com/foo/bar
info:
  description: Package main Car API
  version: "1.0"
paths: {}
produces:
- application/json
responses:
  carResponse:
    schema:
      properties:
        Result:
          format: int64
          type: integer
        Vehicle:
          $ref: '#/definitions/TeslaCar'
      type: object
schemes:
- http
- https
swagger: "2.0"

Environment

swagger version: dev
go version: go1.12 darwin/amd64
OS: macOS 10.14.3