Cannot use Response type hint as dependency annotation

[Kludex]

Privileged issue

• I'm @tiangolo or he asked me directly to create an issue here.

Issue Content

FastAPI 0.95.0 introduced Annotated as a way to create dependencies (https://fastapi.tiangolo.com/release-notes/#0950).

Before 0.95.0, it was possible to use Response as a type hint for dependencies. After that, it was not possible anymore.

• See Cannot specify `Depends` for type Response, yet docs imply you can? #9897 for more details - Thanks @holyoaks for the report.

Example that worked before:

from typing import Annotated
from fastapi import FastAPI, Response, Depends

app = FastAPI()

def set_no_cache_headers(response: Response) -> Response:
    response.headers["Potato"] = "potato"
    return response

@app.get("/")
def testing_response(response: Response = Depends(set_no_cache_headers)):
    return {}

As a workaround today, if you remove the Response type hint, it works as expected:

@app.get("/")
def testing_response(response = Depends(set_no_cache_headers)):
    return {}

The Annotated way also doesn't work:

@app.get("/")
def testing_response(response: Annotated[Response, Depends(set_no_cache_headers)]):
    return {}

[iudeen]

Given how obvious the block is in code, should we assume that it was intentional and update the docs?

[ahmedabdou14]

Hi, any update on this issue?

There is a similar issue to this one aswell

Given a response defined in the api parameters

This code produces a Error: response status is 502

@router.get("/test")
def test(res: Response):
    # res.status_code = 200
    return res

last error log

File "/usr/local/lib/python3.12/site-packages/uvicorn/protocols/http/h11_impl.py", line 488, in send
reason = STATUS_PHRASES[status]

However if we change anything in the response

It works

@router.get("/test")
def test(res: Response):
    res.status_code = 200
    return res

This is very weird because the default value of the Response.status_code is 200 anyway.
I was not able to understand how exactly can a Response be put in the endpoint parameter list without Depends as it will not be explicitly initialized.

The couple of errors presented by @Kludex & the one I reported above means maybe we need a big refactor on how Response class works? It has been over a year on this issue; I wonder why it has been up all this time ^^. Thank you

[ShreySinha02]

Hii,
is this issue is related to this part of code can you please guide me on this

responses: Annotated[
            Optional[Dict[Union[int, str], Dict[str, Any]]],
            Doc(
                """
                Additional responses that could be returned by this *path operation*.

                It will be added to the generated OpenAPI (e.g. visible at `/docs`).
                """
            ),
        ] = None,