Generate client using oneOf in request body works wrong

[Egor-mn]

Generating client that has request body with oneOf leads to problem with creating valid request. Generated models has invalid inheriting and seems like one json body model is redundant

Version: 2.0.0

Example Spec

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Swagger Petstore
paths:
  /pets:
    patch:
      requestBody:
        $ref: '#/components/requestBodies/CreatePetRequestBody'
      responses:
        '200':
          description: Updated
  
components:
  requestBodies:
    CreatePetRequestBody:
      content:
        application/json:
          schema:
            oneOf:
              - $ref: '#/components/schemas/Cat'
              - $ref: '#/components/schemas/Dog'
  schemas:
    Dog:
      type: object
      properties:
        bark:
          type: boolean
        breed:
          type: string
          enum: [Dingo, Husky, Retriever, Shepherd]
    Cat:
      type: object
      properties:
        hunts:
          type: boolean
        age:
          type: integer

oapi-codegen -package api -generate types,client pet.openapi.yaml > client.gen.go

client.gen.go

type ClientWithResponsesInterface interface {
	...
	PatchPetsWithResponse(ctx context.Context, body PatchPetsJSONRequestBody, reqEditors ...RequestEditorFn) (*PatchPetsResponse, error)
}

// PatchPetsJSONRequestBody defines body for PatchPets for application/json ContentType.
type PatchPetsJSONRequestBody PatchPetsJSONBody

// PatchPetsJSONBody defines parameters for PatchPets.
type PatchPetsJSONBody struct {
	union json.RawMessage
}

// CreatePetRequestBody defines model for CreatePetRequestBody.
type CreatePetRequestBody struct {
	union json.RawMessage
}

Generated models CreatePetRequestBody and PatchPetsJSONBody with the same go type definition. PatchPetsJSONBody has no methods at all, bcs of that marshalled request is empty, but CreatePetRequestBody has AsPet / AsDog / Marshal / Unmarshal methods.

Seems like it should be type PatchPetsJSONRequestBody CreatePetRequestBody

and model PatchPetsJSONBody should be deleted

[jamietanna]

FYI this is the same issue as @lzurbriggen noted in https://github.com/oapi-codegen/oapi-codegen/pull/1178#issuecomment-1772263434

FYI, i tried this fork on a schema i had issues with. i have a scenario where the fix outputs the same struct twice:

      operationId: myOperation
      responses:
        "200":
          content:
            application/something.v1+json:
              schema:
                type: array
                items:
                  type: object
                  oneOf:
                  - $ref: '#/components/schemas/Ref1'
                  - $ref: '#/components/schemas/Ref2'
                  - $ref: '#/components/schemas/Ref3'
            application/json:
              schema:
                type: array
                items:
                  type: object
                  oneOf:
                  - $ref: '#/components/schemas/Ref1'
                  - $ref: '#/components/schemas/Ref2'
                  - $ref: '#/components/schemas/Ref3'

output:

type MyOperation_200_Item struct {
	union json.RawMessage
}
type MyOperation_200_Item struct {
	union json.RawMessage
}

i don't know why the schema looks the way it does and i have no control over it, but it seems to be valid.