`warnings.filter` has incorrect type hints for message and module

[aaronzo]

Bug report

Bug description:

the message and module fields in warnings.filters type-check as strings but can be of type re.Pattern:

import warnings
from typing import TYPE_CHECKING

warnings.filterwarnings("ignore", message="hello.+", module="somemod")
if TYPE_CHECKING:
    reveal_type(warnings.filters)  # Sequence[tuple[str, str | None, type[Warning], str | None, int]]

[type(x) for x in warning.filters[0]]  # (<class 'str'>, <class 're.Pattern'>, <class 'type'>, <class 're.Pattern'>, <class 'int'>)

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[srittau]

In fact, it seems it's always an re.Pattern (if not None). PR welcome!

[aaronzo]

Had a look in the codebase and found this ominous comment next to the relevant line: https://github.com/python/typeshed/blob/a6fb689ff163d799dbf30871479c9fc8b5165647/stdlib/warnings.pyi#L28

Not sure why this comment is here, or why it's a bad idea to correct a type for an attribute (which is public by naming convention) whether it's documented or not.

[JelleZijlstra]

"mutate" here probably means you shouldn't mutate it at runtime (e.g., append to the list), not that we can't fix the type. Please do mutate the type so it's correct.

[aaronzo]

Opened #12866 :)

[aaronzo]

Was just playing around with this and noticed that the filters when you start an interpreter include:

('default', None, <class 'DeprecationWarning'>, '__main__', 0)

So it seems that in face you can have a string in the list @srittau - so we might have to amend this. I wonder why this one filter has a different type...