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## Summary Based on the suggestion in https://github.com/astral-sh/ruff/issues/20774#issuecomment-3383153511, I added rendering of unsupported syntax errors in our `format` test. In support of this, I added a `DummyFileResolver` type to `ruff_db` to pass to `DisplayDiagnostics::new` (first commit). Another option would obviously be implementing this directly in the fixtures, but we'd have to import a `NotebookIndex` somehow; either by depending directly on `ruff_notebook` or re-exporting it from `ruff_db`. I thought it might be convenient elsewhere to have a dummy resolver, for example in the parser, where we currently have a separate rendering pipeline [copied](https://github.com/astral-sh/ruff/blob/main/crates/ruff_python_parser/tests/fixtures.rs#L321) from our old rendering code in `ruff_linter`. I also briefly tried implementing a `TestDb` in the formatter since I noticed the `ruff_python_formatter::db` module, but that was turning into a lot more code than the dummy resolver. We could also push this a bit further if we wanted. I didn't add the new snapshots to the black compatibility tests or to the preview snapshots, for example. I thought it was kind of noisy enough (and helpful enough) already, though. We could also use a shorter diagnostic format, but the full output seems most useful once we accept this initial large batch of changes. ## Test Plan I went through the baseline snapshots pretty quickly, but they all looked reasonable to me, with one exception I noted below. I also tested that the case from #20774 produces a new unsupported syntax error.
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.