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Upgrading ruff 0.11 to 0.12

Breaking0.11.13 → 0.12.12Breaking6Deprecated1New32Changed50Fixed100Other70

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BreakingUpgrade verdict

6 breaking changes.

In plain terms
  • When no Python version is configured, Ruff assumes 3.13 for syntax error checks to avoid false alarms, but still assumes 3.9 for lint rules.
  • The Rust toolchain file is no longer shipped in source packages, so packagers can build with their own MSRV-compatible Rust version.
  • The S320 lint rule has been removed.
  • Ruff now flags code that uses newer Python syntax on older versions, and other syntax mistakes the Python compiler itself would reject.
Must act Top 4 of 7 that need code or config changes

What you must change

Breaking6
Ruff defaults to the latest supported Python version (3.13) when checking version-related syntax errors; other defaults remain 3.9.
0.12.0GitHub ReleaseSummarizedView source
Source distributions no longer include rust-toolchain.toml, so downstream maintainers are not forced onto Ruff's development Rust toolchain.
rust-toolchain.toml
0.12.0GitHub ReleaseSummarizedView source
Removes the suspicious-xmle-tree-usage rule (S320).
S320
0.12.0GitHub ReleaseSummarizedView source
Ruff now detects version-related syntax errors and CPython compiler syntax errors, such as irrefutable match patterns.
0.12.0GitHub ReleaseSummarizedView source
Ruff formats multi-line f-strings with format specifiers without adding a line break after the specifier, matching Python 3.13.4 grammar.
0.12.0GitHub ReleaseSummarizedView source
non-pep604-annotation-union (UP007) is split into two rules: UP007 now applies only to typing.Union, while UP045 checks typing.Optional.
UP007UP045
0.12.0GitHub ReleaseSummarizedView source

Deprecations to plan for

Deprecated1
Deprecates the pandas-df-variable-name rule.
0.12.0GitHub ReleaseSummarizedView source