Different results in Python 3.12.1 vs Python 3.12.2

[tfeldmann]

Small reproducer:

from dataclasses import dataclass

from typing_extensions import Protocol, runtime_checkable


@runtime_checkable # removing this decorator fixes the bug.
class HasConfig(Protocol):
 pass

@runtime_checkable
class Action(HasConfig, Protocol):
 pass

@dataclass
class Delete:
 pass

delete = Delete()
print(isinstance(delete, Action))

This prints False in 3.12.2, True in 3.12.1. Changing the import to from typing import Protocol, runtime_checkable also makes this bug disappear.

[AlexWaygood]

This is because Python 3.12.2 changed the implementation of @runtime_checkable so that it now adds an attribute to the class it decorates, and the latest release of typing_extensions just re-exports the typing module's version of the @runtime_checkable rather than defining its own version.

We've actually already fixed this bug on the typing_extensions main branch (in 004b893), but the fix hasn't been released yet.

@JelleZijlstra -- thoughts on possibly reconsidering #324 (comment)? I think it might be worth cutting a patch release for this :/ Sorry for the bother :(

[JelleZijlstra]

I feel the changes are too big for a bugfix release. I merged the PEP 742 implementation and hopefully we can also get PEP 728 implemented in the next few days, then make a release on Sunday (#337).

[AlexWaygood]

typing_extensions 4.10.0 has now been released, which should hopefully fix the issue! Let us know if you're still having problems @tfeldmann