extend-immutable-calls doesn't work on Python scripts (as opposed to modules)

[fofoni]

Keywords: extend-immutable-calls, B008, script, module, __main__
Ruff version: 0.3.7

Working MWE

In a directory containing just the file test.py:

from other_module import A

def f(a=A()):
    pass

checking with:

ruff check --isolated --select=B008 \
    --config 'lint.flake8-bugbear.extend-immutable-calls=["other_module.A"]' \
    test.py

yields no errors.

Buggy MWE

If I declare A in the script instead of importing it:

class A: pass

def f(a=A()):
    pass

now ruff will find a B008 error in the def line, no matter what I configure in extend-immutable-calls. I tried A, test.A, __main__.A, and even builtins.A and __builtins__.A. Nothing makes it recognize A() as an immutable call.

[charliermarsh]

Hmm yeah... We need some way to identify A, and if you pass a script, we probably can't find a module root against which to resolve the path.

[charliermarsh]

__main__.A is kind of interesting.

[fofoni]

(Updated the OP to note that I also tried with test.A.)

__main__.A is kind of interesting.

I tried __main__.A because I didn't know what would work and was exploring possibilities, but I'm not sure if like it: after all, depending on how you invoke Python, any .py file could be the __main__ module. In the end, fully-qualified names aren't really well-defined statically -- you need to look them up in sys.path and follow import hooks etc (mypy can sometimes run into a similar problem).

Since ruff interprets module paths statically, I think the best thing to do in this case would be to check that test.py is not contained in an import package (i.e. not alongside an __init.__.py) and then accept test.A as A's fully-qualified name.

[charliermarsh]

That seems reasonable to me.