Allow to ignore B008 (function calls in default arguments) in cases where the function is a method of a local variable

[beneyal]

Hey all,

First, I want to thank the maintainers of this tool for doing a spectacular job, Ruff is a joy to use! 🚀

I'll begin the issue with a small reproduction:

class A:
    pass


class B:
    def f(self) -> A:
        return A()


def foo(b: B) -> None:
    def bar(x: A = b.f()) -> None:  # Do not perform function call `b.f` in argument defaults; instead, perform the call within the function, or read the default from a module-level singleton variable [B008]
        print(x)

    bar(A())

When using flake8-bugbear's extend-immutable-calls section, I could ignore b.f. In Ruff, I can't, because I don't have a fully qualified path to it. I tried adding B.f to extend-immutable-calls, but it didn't work.

Is there a way to ignore such a thing using extend-immutable-calls? Thanks! 🙏

[MichaReiser]

Thanks for the kind words.

Hmm, no, I don't think there's a way to do it today. Ruff's code that is used to resolve a name (e.g. B.b) doesn't understand following arguments but it would be required to understand that b is typed as B.

Relevant code

ruff/crates/ruff_python_semantic/src/model.rs

Line 938 in c0b7c36

pub fn resolve_qualified_name<'name, 'expr: 'name>(

[beneyal]

Oh, okay, thanks! Should I keep the issue open as a "feature request", or just close it?

[MichaReiser]

I'd leave it open for now. It might be possible to add (limited) support for it with Ruff's current model.