autodoc_type_aliases does not resolve in 3.10

[snorthman]

Describe the bug

I expected

autodoc_type_aliases = {'AliasType': 'mymodule.alias.AliasType'}

to work, but it does nothing in python 3.10, where

from __future__ import annotations

should be unnecessary

How to Reproduce

# alias.py in mymodule
AliasType = int | float

def func() -> AliasType:
  return 0

# conf.py
autodoc_type_aliases = {'AliasType': 'mymodule.alias.AliasType'}

Expected behavior

Resulting build to show

func() -> AliasType

but instead we still find

func() -> int | float

Your project

.

Screenshots

No response

OS

Win

Python version

3.10

Sphinx version

4.5.0

Sphinx extensions

sphinx.ext.autodoc

Extra tools

No response

Additional context

No response

[tk0miya]

from future import annotations

should be unnecessary

Why do you think so? AFAIK, it's still needed.

[JasonGrace2282]

In addition, autodoc should link the return value of func() to the definition if possible.

[picnixz]

Actually, the return type is not formatted at the same place as the parameters list and that's why you end up with signatures where you don't have clickable types.

This is a bug but since autodoc may be completely rewritten at some point, I think we shouldn't implement something that may change entirely in the future. Nothing is planned yet but I am sorry that we probably won't fix this one before deciding what to do with autodoc itself.

[electric-coder]

@picnixz this can work if using a workaround, as shown with some further diagnostic in this answer from #10785 .

A couple of additional related notes:

1. This problem will gain renewed traction with Python 3.12's type
2. Sharing a lot of the same functionality, I haven't been able to get napoleon_type_aliases working at all...

[picnixz]

Actually I usually solve these issues by applying my own transformations and resolving references abruptly. However with PEP 695, we need to rethink how we will document type aliases in general, hence I don't want to start something that is likely to be modified.