Getting F821 Undefined name "xyz" for typing.Literal values when imported indirectly

[alisaifee]

Description

Ruff complains with F821 Undefined name "xyz" for the values described in arguments typed as typing.Literal. I was however only able to reproduce this when Literal is imported indirectly (i.e. not from typing import Literal).

As an example, the following file passes all checks:

from typing import Literal

a: Literal["fu", "bar"] = "fu"
a = "bar"

But this does not:

• x.py

  from typing import Literal
  __all__ = ["Literal"]

• y.py

  from x import Literal
  a: Literal["fu", "bar"] = "fu"
  a = "bar"

• Output:

  $ ruff y.py
  y.py:2:12: F821 Undefined name `fu`
  y.py:2:18: F821 Undefined name `bar`
  

• Reproduced without any configuration changes.

• Ruff version:

  $ ruff --version
  ruff 0.0.225
  

[charliermarsh]

Yeah we don't track that the re-exported Literal in that case is the same as typing.Literal.

We do have something to support this use-case though. If you want to treat every member of x as if it's a re-export of a typing member, you can do:

[tool.ruff]
typing-modules = ["x"]

(Relevant docs are here: https://github.com/charliermarsh/ruff#typing-modules)

[charliermarsh]

(The canonical use-case for this is projects that have some kind of compatibility shim over typing and typing-extensions.)

[alisaifee]

Neat, that is exactly the use case (reference).

[alisaifee]

I'll close this as it is clearly pointed out in the documentation (😅)

[charliermarsh]

Oh nice! Good to know that there are more examples of this, and glad it solves your problem :)

[henryiii]

Solves my problem too, thank you! Though I use relative imports, so it seems to not be triggering on from .._compat.typing import Literal. If I change it to absolute, then it works.

[charliermarsh]

Ah good call -- filed as #2005!

[charliermarsh]

@henryiii - Heads up, I also checked out scikit_build_core and verified that (e.g.) F821 errors aren't being triggered for Literals with typing-modules = ["scikit_build_core._compat.typing"].