## Summary fixes: #13813 This PR fixes a bug in the formatting assignment statement when the value is an f-string. This is resolved by using custom best fit layouts if the f-string is (a) not already a flat f-string (thus, cannot be multiline) and (b) is not a multiline string (thus, cannot be flattened). So, it is used in cases like the following: ```py aaaaaaaaaaaaaaaaaa = f"testeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee{ expression}moreeeeeeeeeeeeeeeee" ``` Which is (a) `FStringLayout::Multiline` and (b) not a multiline. There are various other examples in the PR diff along with additional explanation and context as code comments. ## Test Plan Add multiple test cases for various scenarios.
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 Black compatibility.
Getting started
The Ruff formatter is available as of Ruff v0.1.2. Head to The Ruff Formatter for usage instructions and a comparison to Black.