✨ Allow None as return type for bodiless responses

[hofrob]

Fixes #9424

If the return annotation of the route function is exactly "None", return None for the typed annotation. This allows the status code 204 No Content to be used.

[github-actions]

📝 Docs preview for commit bb5ef4a at: https://647f33cb7357732441e2ff02--fastapi.netlify.app

[fnep]

I tested this using pip install git+https://github.com/hofrob/fastapi@fix-return-no-content-future-annotations and it fixes my issue in #9723. 👍

[hofrob]

@csbasil I rebased after you approved it.

Are there any plans on merging this PR?

[hofrob]

There's an alternative to this on #5860.

Yes, I thought it's not necessary to get the actual type in this case, since None is a reserved word anyway.

It might be a bit faster to compare the string further up in the stack, but that's probably negligible.

There may be other arguments about using one over the other.

[jc-louis]

@tiangolo can we get this merged? it will fix this issue 🙏

[YuriiMotov]

LGTM

[hofrob]

Rebased on top of current master branch. 3.14 will enable deferred evaluation of annotations (PEP649) by default.

[tiangolo]

Thanks! ☕

I tweaked the implementation to not depend on a literal "None" string and instead handle the NoneType that was not being handled. I also tweaked the test to simplify it and use explicit stringified return types to not depend on the possibly changing behavior of from __future__ import annotations. This is now ready. 🤓 🚀