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Brent Westbrook cbc6863b8c
Fix panic when formatting comments in unary expressions (#21501) 
## Summary

This is another attempt at https://github.com/astral-sh/ruff/pull/21410
that fixes https://github.com/astral-sh/ruff/issues/19226.

@MichaReiser helped me get something working in a very helpful pairing
session. I pushed one additional commit moving the comments back from
leading comments to trailing comments, which I think retains more of the
input formatting.

I was inspired by Dylan's PR (#21185) to make one of these tables:

<table>
                <thead>
                    <tr>
                    <th scope="col">Input</th>
                    <th scope="col">Main</th>
                    <th scope="col">PR</th>
                    </tr>
                </thead>
                <tbody>
<tr>
<td><pre lang="python">
if (
    not
    # comment
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass
</pre></td>
<td><pre lang="python">
if (
    # comment
    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
<td><pre lang="python">
if (
    not
    # comment
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
</tr>
<tr>
<td><pre lang="python">
if (
    # unary comment
    not
    # operand comment
    (
        # comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    )
):
    pass
</pre></td>
<td><pre lang="python">
if (
    # unary comment
    # operand comment
    not (
        # comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    )
):
    pass

</pre></td>
<td><pre lang="python">
if (
    # unary comment
    not
    # operand comment
    (
        # comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    )
):
    pass

</pre></td>
</tr>
<tr>
<td><pre lang="python">
if (
    not # comment
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass
</pre></td>
<td><pre lang="python">
if (  # comment
    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
<td><pre lang="python">
if (
    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  # comment
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
</tr>
</tbody>
            </table>

hopefully it helps even though the snippets are much wider here.

The two main differences are (1) that we now retain own-line comments
between the unary operator and its operand instead of moving these to
leading comments on the operator itself, and (2) that we move
end-of-line comments between the operator and operand to dangling
end-of-line comments on the operand (the last example in the table).

## Test Plan

Existing tests, plus new ones based on the issue. As I noted below, I
also ran the output from main on the unary.py file back through this
branch to check that we don't reformat code from main. This made me feel
a bit better about not preview-gating the changes in this PR.

```shell
> git show main:crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/unary.py | ruff format - | ./target/debug/ruff format --diff -
> echo $?
0
```

---------

Co-authored-by: Micha Reiser <micha@reiser.io>
Co-authored-by: Takayuki Maeda <takoyaki0316@gmail.com>
 		2025-11-18 10:48:14 -05:00
..
resources/test/fixtures Fix panic when formatting comments in unary expressions (#21501) 2025-11-18 10:48:14 -05:00
src Fix panic when formatting comments in unary expressions (#21501) 2025-11-18 10:48:14 -05:00
tests Fix panic when formatting comments in unary expressions (#21501) 2025-11-18 10:48:14 -05:00
CONTRIBUTING.md [ty] AST garbage collection (#18482) 2025-06-13 08:40:11 -04:00
Cargo.toml [`ruff`] Update schemars to v1 (#20942) 2025-10-20 08:59:52 +02:00
README.md Add f-string formatting to the docs (#15367) 2025-01-09 10:20:06 +01:00
generate.py Implement template strings (#17851) 2025-05-30 15:00:56 -05:00
orphan_rules_in_the_formatter.svg Generate FormatRule definitions (#4724) 2023-06-01 08:38:53 +02:00

README.md

Ruff Formatter

The Ruff formatter is an extremely fast Python code formatter that ships as part of the ruff CLI.

Goals

The formatter is designed to be a drop-in replacement for Black, but with an excessive focus on performance and direct integration with Ruff.

Specifically, the formatter is intended to emit near-identical output when run over Black-formatted code. When run over extensive Black-formatted projects like Django and Zulip, > 99.9% of lines are formatted identically. When migrating an existing project from Black to Ruff, you should expect to see a few differences on the margins, but the vast majority of your code should be unchanged.

If you identify deviations in your project, spot-check them against the intentional deviations enumerated below, as well as the unintentional deviations filed in the issue tracker. If you've identified a new deviation, please file an issue.

When run over non-Black-formatted code, the formatter makes some different decisions than Black, and so more deviations should be expected, especially around the treatment of end-of-line comments. For details, see Style Guide.

Getting started

Head to The Ruff Formatter for usage instructions and a comparison to Black.