4.1.2 test suite regressions with Python 3.10.0b4: TypeError: isinstance() arg 2 must be a type, a tuple of types or a union

[mgorny]

Describe the bug

Sphinx 4.1.2's test suite has 367 test failures and 13 errors with Python 3.10.0b4. They all seem to have a common cause in:

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

obj = <class 'autodoc_target.Class'>

    def isNewType(obj: Any) -> bool:
        """Check the if object is a kind of NewType."""
        if sys.version_info >= (3, 10):
>           return isinstance(obj, typing.NewType)
E           TypeError: isinstance() arg 2 must be a type, a tuple of types or a union

obj        = <class 'autodoc_target.Class'>

sphinx/util/inspect.py:215: TypeError

How to Reproduce

$ git clone https://github.com/sphinx-doc/sphinx
$ cd sphinx
$ tox -e py310

Expected behavior

No response

Your project

n/a

Screenshots

No response

OS

Gentoo Linux

Python version

3.10.0b4

Sphinx version

4.1.2 (+ git master)

Sphinx extensions

No response

Extra tools

No response

Additional context

Full superverbose build log (17M): dev-python:sphinx-4.1.2:20210727-064745.log

[mgorny]

This is how a similar problem was fixed in hypothesis: https://github.com/HypothesisWorks/hypothesis/pull/3044/files

[tk0miya]

Oops... the change of NewType was introduced after b4 release. It will be included in the next release (rc1?). Could you wait for it for a while?

[mgorny]

That would effectively mean we can't package new Sphinx version until it happens. Can't you just extend sys.version_info check to include beta5?

[psss]

Hi, seems one of our tests is failing on this on Fedora Rawhide.

Could you wait for it for a while?

Sure, but how roughly long is "a while"? :) Is it worth disabling failing tests or will it be fixed soon?

[abravalheri]

Hello, I also found the same error when running sphinx-build ... / python -m sphinx ... on Python 3.10.0b4 on my project (not related to sphinx test suite).

[tk0miya]

3.10.0rc1 will be released next Monday. IMO, it's not too far.
https://www.python.org/dev/peps/pep-0619/#schedule

[abravalheri]

Aaah, OK, I see, so sphinx should be compatible with 3.10.0rc1, right?

That is wonderful news, thank you very much @tk0miya 👏

[tk0miya]

Yes, we're using the HEAD of 3.10 for testing. So it will be compat with 3.10.0rc1. (But I can't promise that because it's still fragile)

[mgorny]

And so it turns out that due to other last minute changes, sphinx 4.1.2 is compatible neither with 3.10.0b4 nor with 3.10.0rc1.