F401 unused-import for star-imports: false negative?

[spaceone]

flake8 and ruff differ for * imports:

$ flake8 - <<<"from foo import *"
stdin:1:1: F403 'from foo import *' used; unable to detect undefined names
stdin:1:1: F401 'foo.*' imported but unused
$ ruff - <<<"from foo import *"
-:1:1: F403 `from foo import *` used; unable to detect undefined names
Found 1 error.

I detected this as prior it had a # noqa: F401 comment which was removed by RUF100 when I compared any leftovers with flake8.

[spaceone]

I filed an upstream bug: PyCQA/pyflakes#766
I would vote for fixing it in pyflakes.

[spaceone]

So they think that if F405 doesn't occur they mark the star import as F401.

F405 can be triggered by:

$ python3 -m pyflakes <<< $'from foo import *; __all__ = ("a",)'
<stdin>:1:1: 'from foo import *' used; unable to detect undefined names
<stdin>:1:20: 'a' may be undefined, or defined from star imports: foo
$ python3 -m pyflakes <<< $'from foo import *; a'
<stdin>:1:1: 'from foo import *' used; unable to detect undefined names
<stdin>:1:20: 'a' may be undefined, or defined from star imports: foo

[charliermarsh]

I think I'm okay with Ruff's behavior here but open to being convinced otherwise. What do you think?

[spaceone]

I am unsure. I like ruffs behavior more. Will think what I can do for the time I need to support both flake8 and ruff (aka: until #2402 is fixed).

[ngnpope]

For a file containing just the following (which is often seen in __init__.py):

from math import *

❯ flake8 bug.py
bug.py:1:1: F403 'from math import *' used; unable to detect undefined names
bug.py:1:1: F401 'math.*' imported but unused
❯ ruff bug.py 
bug.py:1:1: F403 `from math import *` used; unable to detect undefined names
Found 1 error.

Using something from the math module:

from math import *
pi

❯ flake8 bug.py
bug.py:1:1: F403 'from math import *' used; unable to detect undefined names
bug.py:2:1: F405 'pi' may be undefined, or defined from star imports: math
❯ ruff bug.py 
bug.py:1:1: F403 `from math import *` used; unable to detect undefined names
bug.py:2:1: F405 `pi` may be undefined, or defined from star imports: `math`
Found 2 errors.

Using something that is not in the math module:

from math import *
invalid_name

❯ flake8 bug.py
bug.py:1:1: F403 'from math import *' used; unable to detect undefined names
bug.py:2:1: F405 'invalid_name' may be undefined, or defined from star imports: math
❯ ruff bug.py 
bug.py:1:1: F403 `from math import *` used; unable to detect undefined names
bug.py:2:1: F405 `invalid_name` may be undefined, or defined from star imports: `math`
Found 2 errors.

It has always bugged me getting F401 and F403 when the latter feels like it gives the expectation of the former, so I do quite like the way ruff does this... But I wouldn't be upset if it was implemented like the original.

[charliermarsh]

Going to close for now because I'm comfortable with our current behavior.

[enriquebos]

I think if all is defined it should recognize the star import, only throw if all is also undefined.

[niniack]

I think if all is defined it should recognize the star import, only throw if all is also undefined.

I think I agree with this, but it would be good to hear if someone thinks there is a reason why this is bad practice for __init__.py files. Anyways, it was really bothering me so I used the following in my pyproject.toml, adapted from here

[tool.ruff.lint.per-file-ignores]
"__init__.py" = ["F401", "F403"]