typing_extensions.Literal reimport is not "detected"

[ashb]

As part of the Airflow project we have an airflow.typing_compat module that has this in it https://github.com/apache/airflow/blob/71306b31f1842ee2b1eb1cc2980b90f0fb6b11dc/airflow/typing_compat.py#L38-L41:

if sys.version_info >= (3, 9):
    from typing import Literal
else:
    from typing_extensions import Literal

Ruff right now doesn't detect this use of Literal and tries to resolve the value inside it as a type:

% echo 'from airflow.typing_compat import Literal; from typing import Union; X = Union[Literal[False], Literal["db"]]' | \
  ruff - --line-length=999
-:1:104: F821 Undefined name `db`

[charliermarsh]

The problem here is that we don't track imports across modules, so we can't tell (right now) that Literal there is coming from typing or typing_extensions.

I could see two ways to fix this in the short term:

1. I could special-case airflow.typing_compat within Ruff for now. It's easy to do on my end, though obviously a bit awkward :)
2. We could add a configuration option to treat a module as a typing re-exporter. The pattern you have here seems somewhat general, so this seems like a reasonable thing to have.

[charliermarsh]

E.g., would something like this work for Airflow?

[tool.ruff]
typing-exports = ["airflow.typing_compat"]

[ashb]

E.g., would something like this work for Airflow?

[tool.ruff]
typing-exports = ["airflow.typing_compat"]

Yup that would do it for us

[charliermarsh]

Cool, I'll ship that for you today.

[charliermarsh]

Going out in v0.0.217.