Sourced from ruff's releases.

0.9.0

Release Notes

Check out the blog post for a migration guide and overview of the changes!

Breaking changes

Ruff now formats your code according to the 2025 style guide. As a result, your code might now get formatted differently. See the formatter section for a detailed list of changes.

This release doesn’t remove or remap any existing stable rules.

Stabilization

The following rules have been stabilized and are no longer in preview:

• stdlib-module-shadowing (A005). This rule has also been renamed: previously, it was called builtin-module-shadowing.
• builtin-lambda-argument-shadowing (A006)
• slice-to-remove-prefix-or-suffix (FURB188)
• boolean-chained-comparison (PLR1716)
• decimal-from-float-literal (RUF032)
• post-init-default (RUF033)
• useless-if-else (RUF034)

The following behaviors have been stabilized:

• pytest-parametrize-names-wrong-type (PT006): Detect pytest.parametrize calls outside decorators and calls with keyword arguments.
• module-import-not-at-top-of-file (E402): Ignore pytest.importorskip calls between import statements.
• mutable-dataclass-default (RUF008) and function-call-in-dataclass-default-argument (RUF009): Add support for attrs.
• bad-version-info-comparison (PYI006): Extend the rule to check non-stub files.

The following fixes or improvements to fixes have been stabilized:

• redundant-numeric-union (PYI041)
• duplicate-union-members (PYI016)

Formatter

This release introduces the new 2025 stable style (#13371), stabilizing the following changes:

• Format expressions in f-string elements (#7594)
• Alternate quotes for strings inside f-strings (#13860)
• Preserve the casing of hex codes in f-string debug expressions (#14766)
• Choose the quote style for each string literal in an implicitly concatenated f-string rather than for the entire string (#13539)
• Automatically join an implicitly concatenated string into a single string literal if it fits on a single line (#9457)
• Remove the ISC001 incompatibility warning (#15123)
• Prefer parenthesizing the assert message over breaking the assertion expression (#9457)
• Automatically parenthesize over-long if guards in match case clauses (#13513)
• More consistent formatting for match case patterns (#6933)
• Avoid unnecessary parentheses around return type annotations (#13381)

... (truncated)

Sourced from ruff's changelog.

0.9.0

Check out the blog post for a migration guide and overview of the changes!

Breaking changes

Ruff now formats your code according to the 2025 style guide. As a result, your code might now get formatted differently. See the formatter section for a detailed list of changes.

This release doesn’t remove or remap any existing stable rules.

Stabilization

The following rules have been stabilized and are no longer in preview:

• stdlib-module-shadowing (A005). This rule has also been renamed: previously, it was called builtin-module-shadowing.
• builtin-lambda-argument-shadowing (A006)
• slice-to-remove-prefix-or-suffix (FURB188)
• boolean-chained-comparison (PLR1716)
• decimal-from-float-literal (RUF032)
• post-init-default (RUF033)
• useless-if-else (RUF034)

The following behaviors have been stabilized:

• pytest-parametrize-names-wrong-type (PT006): Detect pytest.parametrize calls outside decorators and calls with keyword arguments.
• module-import-not-at-top-of-file (E402): Ignore pytest.importorskip calls between import statements.
• mutable-dataclass-default (RUF008) and function-call-in-dataclass-default-argument (RUF009): Add support for attrs.
• bad-version-info-comparison (PYI006): Extend the rule to check non-stub files.

The following fixes or improvements to fixes have been stabilized:

• redundant-numeric-union (PYI041)
• duplicate-union-members (PYI016)

Formatter

This release introduces the new 2025 stable style (#13371), stabilizing the following changes:

• Format expressions in f-string elements (#7594)
• Alternate quotes for strings inside f-strings (#13860)
• Preserve the casing of hex codes in f-string debug expressions (#14766)
• Choose the quote style for each string literal in an implicitly concatenated f-string rather than for the entire string (#13539)
• Automatically join an implicitly concatenated string into a single string literal if it fits on a single line (#9457)
• Remove the ISC001 incompatibility warning (#15123)
• Prefer parenthesizing the assert message over breaking the assertion expression (#9457)
• Automatically parenthesize over-long if guards in match case clauses (#13513)
• More consistent formatting for match case patterns (#6933)
• Avoid unnecessary parentheses around return type annotations (#13381)
• Keep the opening parentheses on the same line as the if keyword for comprehensions where the condition has a leading comment (#12282)

... (truncated)

• d0b2bbd Release 0.9.0 (#15371)
• 8628f16 [ruff] Stop parsing diagnostics from other sources for code action requests...
• 8bc11c4 [flake8-django] Recognize other magic methods (DJ012) (#15365)
• bf5b0c2 [red-knot] Minor refactor of red_knot_vendored/build.rs (#15372)
• 097aa04 [red-knot] Typeshed patching: use build.rs instead of workflow (#15370)
• f706c3f Add f-string formatting to the docs (#15367)
• 29f6653 [ruff] Stabilize useless-if-else (RUF034) (#15351)
• d645525 [pylint]: Stabilize boolean-chained-comparison (PLR1716) (#15354)
• 6dcf7b3 [ruff] Stabilize post-init-default (RUF033) (#15352)
• 943d4fc Update formatter preview documentation (#15349)
• Additional commits viewable in compare view

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