🐛 Fix empty reponse body when default status_code is empty but the a Response parameter with response.status_code is set

[tmeckel]

This PR contains a fix to a bug which cleared the reponse content if the status code is changed via a Resource parameter described in the documentation.

Sample code which creates an empty response body:

@app.delete(
    "/{id}",
    responses={
        204: {"model": None, "description": "No Content"},
    },
    status_code=204,
)
async def delete_deployment(
    id: str = Path(None),
    response: Response = None,
) -> None:
    response.status_code = 400
    return {"msg": "Status overwritten"}

[codecov]

Codecov Report

Merging #5360 (9bf2b96) into master (c4007cb) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #5360   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          539       540    +1     
  Lines        13918     13936   +18     
=========================================
+ Hits         13918     13936   +18     

Impacted Files	Coverage Δ
fastapi/routing.py	100.00% <100.00%> (ø)
tests/test_reponse_set_reponse_code_empty.py	100.00% <100.00%> (ø)

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[github-actions]

📝 Docs preview for commit 834bb6d at: https://6318c7d257bf16323c910a72--fastapi.netlify.app

[iudeen]

Did you check if proper response code is reflecting in the api doc?

In Doc, it still shows 204. This PR would be complete if that is handled as well, IMHO.

[github-actions]

📝 Docs preview for commit a942d46 at: https://6319ffa9c38fb201c2c7a290--fastapi.netlify.app

[tmeckel]

@iudeen can you elaborate what you mean by "...proper response code is reflecting in the api doc?" As you can see from the referenced link to the documentation it's supported to override the response code by setting the code on a Reponse parameter object to the API method.

[iudeen]

can you elaborate what you mean by "...proper response code is reflecting in the api doc?"

I was meaning to say if we change response codes, it should reflect in Swagger (or Redoc) docs as well. But I now realize this behavior was not there before as well and seems its out of scope for this PR.

LGTM! as it avoids the error below

RuntimeError: Response content shorter than Content-Length

👍

[tiangolo]

Awesome, thank you @tmeckel! 🚀 🍰

I updated the tests a bit to simplify them and cover OpenAPI (what can be supported).

@iudeen thanks for the interest, but the custom response code here is done only at runtime, there's no way to put that in OpenAPI, so that wouldn't apply here.

Thanks! ☕