Regression in mypy 0.930: object.__reduce__

[dvarrazzo]

In mypy 0.930 the signature for object.__reduce__ has been changed to

    def __reduce__(self) -> str | Tuple[object, ...]: ...

This is wrong, reading the documentation. The following valid code now is reported as error:

from typing import Any, Tuple, Union


class Diagnostic:
    def __reduce__(self) -> Union[str, Tuple[Any, ...]]:
        res = super().__reduce__()
        if isinstance(res, tuple) and len(res) >= 3:
            res[2]["_info"] = 42

        return res

[dvarrazzo]

Note: broken in 88f86a0

[srittau]

Yeah, the return type of __reduce__ is documented, so we should revert this change. Cc @AlexWaygood

[AlexWaygood]

Yes, my bad. Needs to be reverted, agreed.

[hauntsaninja]

@dvarrazzo this should be fixed in mypy 0.931, even if python/mypy#11820 isn't

[dvarrazzo]

Yes, this is fixed alright :)

• You can see a 0.931 run failing on Daily tests failed on Wed Apr 24 2024 #11820 at https://github.com/psycopg/psycopg/runs/4741795872?check_suite_focus=true
• This run with 0.930 shows both the bugs: https://github.com/psycopg/psycopg/runs/4610348714?check_suite_focus=true