Feature request: make typing_modules configurable

[bersbersbers]

The typeguard package enables run-time type checks. One of the drawbacks of run-time type checks is that type annotations behind if typing.TYPE_CHECKING are not visible (https://typeguard.readthedocs.io/en/stable/userguide.html#notes-on-forward-reference-handling; compare also agronholm/typeguard#456).

So this passes in python bug.py while it shouldn't (ideally):

bug.py

from typing import TYPE_CHECKING

from typeguard import typechecked

if TYPE_CHECKING:
    A = int

@typechecked
def bug() -> None:
    a: A = 1.5
    print(a)

bug()

One workaround that I am investigating is to use a project-local typing_ module from which I import my own TYPE_CHECKING, like this:

typing_.py

from typing import TYPE_CHECKING as _TYPE_CHECKING

def enable_runtime_typing_checks() -> bool:
    return True  # more complicated, obviously

TYPE_CHECKING = _TYPE_CHECKING or enable_runtime_typing_checks()

workaround.py

from typeguard import typechecked

from typing_ import TYPE_CHECKING

if TYPE_CHECKING:
    A = int

@typechecked
def bug() -> None:
    a: A = 1.5
    print(a)

bug()

Then, python workaround.py fails as expected:

Traceback (most recent call last):
  File "C:\Code\project\workaround.py", line 15, in <module>
    bug()
  File "C:\Code\project\workaround.py", line 11, in bug
    a: A = 1.5
  File "c:\Code\project\.venv\Lib\site-packages\typeguard\_functions.py", line 251, in check_variable_assignment
    check_type_internal(value, annotation, memo)
  File "c:\Code\project\.venv\Lib\site-packages\typeguard\_checkers.py", line 784, in check_type_internal
    raise TypeCheckError(f"is not an instance of {qualified_name(origin_type)}")
typeguard.TypeCheckError: value assigned to a (float) is not an instance of int

but A is not used at runtime. Nice!

(Obviously, my real A is more complicated than that, and my example above is too simplistic as it fails on letting enable_runtime_typing_checks return False - anyway, I guess this is enough to make the following main point.)

When I apply this concept more generally, though:

code.py

from typing_ import TYPE_CHECKING

if TYPE_CHECKING:
    from pathlib import Path

    from typing_ import A

def bug() -> None:
    a: A = 1.5
    print(a)
    p: Path

bug()

ruff check --isolated --select=TCH003 code.py

gives me

code.py:4:25: TCH003 Move standard library import `pathlib.Path` into a type-checking block

So, long story short: can I make ruff understand my own typing_.TYPE_CHECKING as a type-checking block, similar to typing.TYPE_CHECKING and typing_extensions.TYPE_CHECKING (compare #8429)?

[AlexWaygood]

Hi, thanks for the issue! We already have a typing-modules configuration option: https://docs.astral.sh/ruff/settings/#lint_typing-modules. Does that do what you're asking for here?

[bersbersbers]

@AlexWaygood absolutely, thank you! I feel somewhat embarrassed since I remember asking a similar question before, but could not find it in my emails or otherwise (I now know it's #5400). I also searched the repository for typing_modules and did not find much, and I checked ruff check . --show-settings and could not find it there (although I clearly see it now).

I think the main reason why I went looking is because I checked https://docs.astral.sh/ruff/rules/typing-only-standard-library-import/ first, and the rule did not mention the configuration option. Maybe it should be added there (any in other TCH rules) to make it more discoverable.