Files
ruff/python/ruff-ecosystem
Brent Westbrook 947179d7c6 Enable lint.preview and missing default rules in our Ruff config (#28112)
Summary
--

This PR updates our ruff-pre-commit dependency to 0.16.5, which supports
the new category selectors,
and then enables `lint.preview` and the new default categories so that
we can dogfood them on our
code. There were 66 diagnostics initially, which I also fixed or
ignored:

```
28	FURB113 	[ ] repeated-append
12	ASYNC240	[ ] blocking-path-method-in-async-function
 6	RUF105  	[*] noqa-comments
 5	PLW1510 	[ ] subprocess-run-without-check
 3	PLW0108 	[ ] unnecessary-lambda
 2	EXE001  	[ ] shebang-not-executable
 2	RUF039  	[*] unraw-re-pattern
 1	B024    	[ ] abstract-base-class-without-abstract-method
 1	FURB142 	[*] for-loop-set-mutations
 1	PERF102 	[ ] incorrect-dict-iterator
 1	PLC0207 	[*] missing-maxsplit-arg
 1	PLW0127 	[ ] self-assigning-variable
 1	TRY004  	[ ] type-check-without-type-error
 1	PLW0120 	[*] useless-else-on-loop
 1	TRY201  	[ ] verbose-raise
 ```

Of these, I ignored `repeated-append` and `blocking-path-method-in-async-function`. I think they are
still reasonable defaults, just less useful/important in our uses.

0.16.5 also includes https://github.com/astral-sh/ruff-pre-commit/pull/159, so I removed `markdown` from our main `ruff-format` hook, leaving it for the later mdtest formatting stage.

I also had to make a few changes related to config discovery in tests:
- move our cached ecosystem checkouts to `$RUNNER_TEMP` instead of inside of our checkout
- convert some CLI tests to use the `CliTest` helpers
- add `configurationPreference: editorOnly` to some notebook tests

In these cases, our own Ruff settings were being inherited by test code. This likely affects many other tests, but I only updated the obviously failing ones for now. I'm least confident about the notebook tests, but as far as I can tell from the history (https://github.com/astral-sh/ruff/pull/11944, https://github.com/astral-sh/ruff/pull/22810), the specific diagnostics are not the important parts being asserted.

Test Plan
--

CI on this PR
2026-08-28 12:24:36 -04:00
..

ruff-ecosystem

Compare lint and format results for two different ruff versions (e.g. main and a PR) on real world projects.

Installation

From the Ruff project root, install with uv:

uv tool install -e ./python/ruff-ecosystem

Usage

ruff-ecosystem <check | format> <baseline executable> <comparison executable>

Note executable paths may be absolute, relative to the current working directory, or will be looked up in the current Python environment and PATH.

Run ruff check ecosystem checks comparing your debug build to your system Ruff:

ruff-ecosystem check ruff "./target/debug/ruff"

Run ruff format ecosystem checks comparing your debug build to your system Ruff:

ruff-ecosystem format ruff "./target/debug/ruff"

Run ruff format ecosystem checks comparing with changes to code that is already formatted:

ruff-ecosystem format ruff "./target/debug/ruff" --format-comparison ruff-then-ruff

Run ruff format ecosystem checks comparing with the Black formatter:

ruff-ecosystem format black ruff -v --cache python/checkouts --format-comparison black-and-ruff

The default output format is markdown, which includes nice summaries of the changes. You can use --output-format json to display the raw data — this is particularly useful when making changes to the ecosystem checks.

Development

When developing, it can be useful to set the --pdb flag to drop into a debugger on failure:

ruff-ecosystem check ruff "./target/debug/ruff" --pdb

You can also provide a path to cache checkouts to speed up repeated runs:

ruff-ecosystem check ruff "./target/debug/ruff" --cache ./repos