0ebdebddd8
## Summary This PR makes two changes to our formatting of `lambda` expressions: 1. We now parenthesize the body expression if it expands 2. We now try to keep the parameters on a single line The latter of these fixes #8179: Black formatting and this PR's formatting: ```py def a(): return b( c, d, e, f=lambda self, *args, **kwargs: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa( *args, **kwargs ), ) ``` Stable Ruff formatting ```py def a(): return b( c, d, e, f=lambda self, *args, **kwargs: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(*args, **kwargs), ) ``` We don't parenthesize the body expression here because the call to `aaaa...` has its own parentheses, but adding a binary operator shows the new parenthesization: ```diff @@ -3,7 +3,7 @@ c, d, e, - f=lambda self, *args, **kwargs: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa( - *args, **kwargs - ) + 1, + f=lambda self, *args, **kwargs: ( + aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(*args, **kwargs) + 1 + ), ) ``` This is actually a new divergence from Black, which formats this input like this: ```py def a(): return b( c, d, e, f=lambda self, *args, **kwargs: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa( *args, **kwargs ) + 1, ) ``` But I think this is an improvement, unlike the case from #8179. One other, smaller benefit is that because we now add parentheses to lambda bodies, we also remove redundant parentheses: ```diff @pytest.mark.parametrize( "f", [ - lambda x: (x.expanding(min_periods=5).cov(x, pairwise=True)), - lambda x: (x.expanding(min_periods=5).corr(x, pairwise=True)), + lambda x: x.expanding(min_periods=5).cov(x, pairwise=True), + lambda x: x.expanding(min_periods=5).corr(x, pairwise=True), ], ) def test_moment_functions_zero_length_pairwise(f): ``` ## Test Plan New tests taken from #8465 and probably a few more I should grab from the ecosystem results. --------- Co-authored-by: Micha Reiser <micha@reiser.io>
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.