generate: allOf in response doesn't use $ref

[Kangaroux]

Expected Behavior

Include an embedded struct in a response, label it with swagger:allOf, and expect to see a $ref in the generated schema.

Actual Behavior

The fields are listed as properties

Swagger specification

Note the allOf section for userResponse

This is the actual generated spec:

responses:
  baseResponse:
    description: ""
    headers:
      error:
        description: An error message describing what went wrong
        type: string
      ok:
        description: Whether the request was successful or not
        type: boolean
  userResponse:
    description: ""
    schema:
      allOf:
      - properties:
          error:
            description: An error message describing what went wrong
            type: string
          ok:
            description: Whether the request was successful or not
            type: boolean
        type: object
      - properties:
          user:
            $ref: '#/definitions/User'
        type: object

And this is what should be generated:

responses:
  baseResponse:
    description: ""
    headers:
      error:
        description: An error message describing what went wrong
        type: string
      ok:
        description: Whether the request was successful or not
        type: boolean
  userResponse:
    description: ""
    schema:
      allOf:
      - $ref: '#/responses/baseResponse'
      - properties:
          user:
            $ref: '#/definitions/User'
        type: object

Steps to reproduce

// swagger:response baseResponse
type BaseResponse struct {
	// An error message describing what went wrong
	Error string `json:"error,omitempty"`

	// Whether the request was successful or not
	OK bool `json:"ok"`
}

// swagger:response userResponse
type UserResponse struct {
	// in: body
	Body struct {
		// swagger:allOf
		BaseResponse

		User User `json:"user"`
	}
}

Environment

swagger version: v0.29.0
go version: go1.18 linux/amd64
OS: Pop!_OS 21.04