`ruff format` moves `# noqa` comment to wrong location

[jakob-keller]

I would like to switch my codebase to ruff format, but there is one annoying issue that breaks my use case: Some # noqa comments are moved resulting in issues when calling ruff check.

Hers's a minimal code snippet to demonstrate what happens:

# test.py (original)

import typing


def foo(
    __bar: str,
    /,
    **specifiers: typing.Any,  # noqa: ANN401
) -> int:
    return len(specifiers)

$ ruff --version
ruff 0.3.1

$ ruff check --isolated --select ANN401 test.py

$ ruff format --isolated test.py
1 file reformatted

# test.py (reformatted)

import typing


def foo(
    __bar: str,
    /,  # noqa: ANN401
    **specifiers: typing.Any,
) -> int:
    return len(specifiers)

$ ruff check --isolated --select ANN401 test.py
test.py:7:19: ANN401 Dynamically typed expressions (typing.Any) are disallowed in `**specifiers`
Found 1 error.

I assume this issue is an edge case that has to do with the keyword-only / syntax being used. Are there any workarounds available?

[charliermarsh]

Oh hmm, this looks like a bug, thanks. Will look into it. The only workaround I could think of is using # fmt: skip on the header for now:

import typing


def foo(
    __bar: str,
    /,
    **specifiers: typing.Any,  # noqa: ANN401
) -> int:  # fmt: skip
    return len(specifiers)

[charliermarsh]

This is why we need a programming language that doesn't allow comments 😂

[MichaReiser]

This is why we need a programming language that doesn't allow comments 😂

Or an AST that represents / ;)

FYI: This is not specific to noqa. We incorrectly associate any end-of-line comment **kwargs comment following /

https://play.ruff.rs/cb2a370c-ae53-48a5-a35f-810b9c537ae2

I suspect that the error is somewhere in

ruff/crates/ruff_python_formatter/src/comments/placement.rs

Line 702 in 184241f

fn handle_parameters_separator_comment<'a>(

[jakob-keller]

Thanks @MichaReiser and everyone else at https://github.com/astral-sh! You rock 🚀