Hello 👋

B006 (mutable-argument-default) no longer offers an autofix even when --unsafe-fixes is passed.

Use the example from ruff rule B006 to reproduce this:

# /tmp/bad.py
def add_to_list(item, some_list=[]):
    some_list.append(item)
    return some_list

At HEAD (df807ff) and v0.1.1:

❯ cargo run -p ruff_cli -- check --select B --unsafe-fixes /tmp/bad.py --no-cache
/tmp/bad.py:1:33: B006 Do not use mutable data structures for argument defaults
Found 1 error.

I've bisected this to 22e1874, but that may only be where the issue was surfaced in the CLI.

The output is slightly different in that commit, there's an additional line:

/tmp/bad.py:1:33: B006 Do not use mutable data structures for argument defaults
Found 1 error.
[*] 0 fixable with the --fix option.

If I omit --unsafe-fixes there's a hint about a hidden fix:

❯ cargo run -p ruff_cli -- check --select B /tmp/bad2.py --no-cache
/tmp/bad.py:1:33: B006 Do not use mutable data structures for argument defaults
Found 1 error.
1 hidden fix can be enabled with the `--unsafe-fixes` option.

(I don't see this hint in 0.1.1 or HEAD, but I haven't bisected where it went away.)

In the parent of the bisected commit and in v0.0.292, I get the expected output:

/tmp/bad.py:1:33: B006 [*] Do not use mutable data structures for argument defaults
Found 1 error.
[*] 1 potentially fixable with the --fix option.

(I noticed after the fact that I ran Ruff from its repository which has Ruff config in pyproject.toml, so that could have skewed results a little. But the repro should still be valid.)