Select response model specified in responses based on status code

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Example

Here's a self-contained minimal, reproducible, example with my use case:

from fastapi import FastAPI, Response
from pydantic import BaseModel

api = FastAPI()


class DefaultModel(BaseModel):
    default: str = "yes"


class OtherModel(BaseModel):
    something: str = "something"
    other: str = "other"


@api.get("/test", response_model=DefaultModel, responses={503: {"model": OtherModel}})
def get(response: Response):
    response.status_code = 503
    return OtherModel()

Description

In contradiction to the documentation for the 503 status code, the sample code will result in a reply {"default": "yes"} without any validation errors.

It would be nice if fastapi could select the correct model depending on the status code declared in the response object.

The solution you would like

The code should result in an OtherModel being serialized instead of the default one based on the selected status code.

Describe alternatives you've considered

Using JSONResponse manually is tedious and error prone. At least using a model directly in JSONResponse would be nice instead of having to convert it manually to dict.

Environment

• OS: [e.g. Linux / Windows / macOS]: linux
• FastAPI Version [e.g. 0.3.0]: 0.61.1
• Python version: 3.8.5