astral-sh/ruff

[`Pylint`] `PLE2510` fix causes syntax error inside pre-3.12 f-strings

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#18,816 opened on 2025/06/20

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説明

Summary

If a backspace is inside an f-string replacement while a pre-3.12 version is targeted, the fix for invalid-character-backspace (PLE2510) will introduce a syntax error. This happens both inside a string inside the replacement, and inside the format specs. playground

PS D:\python_projects> Get-Content issue.py

f"{'␈'}"

^ note: I'm cheating here, PowerShell does not actually display the backspace character as ␈, it actually gets displayed as f"{'}"

PS D:\python_projects> uvx ruff check issue.py --isolated --select PLE --target-version py39

issue.py:1:5: PLE2510 [*] Invalid unescaped character backspace, use "\b" instead
  |
1 | f"{'␈'}"
  |     ^ PLE2510
  |
  = help: Replace with escape sequence

Found 1 error.
[*] 1 fixable with the `--fix` option.

PS D:\python_projects> uvx ruff check issue.py --isolated --select PLE --target-version py39 --fix

issue.py:1:5: SyntaxError: Cannot use an escape sequence (backslash) in f-strings on Python 3.9 (syntax was added in Python 3.12)
  |
1 | f"{'\b'}"
  |     ^
  |

Found 2 errors (1 fixed, 1 remaining).

This also applies to PLE2512, PLE2513, and PLE2515 playground, as well as PLE2514, but the playground does not support null chars.

Version

ruff 0.12.0 (87f0feb 2025-06-17) + playground

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調査方針
The bug is in the fix for rule PLE2510 (invalid character backspace) in Ruff. The fix incorrectly inserts a backslash escape inside f string replacements when targeting Python <3.12. Look at the rule implementation in crates/ruff linter/src/rules/pylint/rules/invalid character.rs. The fix logic needs to detect whether the replacement is inside an f string and if the target version does not support backslash escapes in f strings. Also check similar rules PLE2512, PLE2513, PLE2514, PLE2515. Consider adding a check to avoid applying the fix in such contexts, or generate an alternative fix like using a Unicode escape. Review existing test cases in tests/ to cover this scenario.
技術スタック
pythonrust
領域
tooling
Issue 種別
バグ
難度新しい貢献者にとっての実装難度です。1 は非常に小さな変更、5 は専門的な作業です。
3
推定時間経験ある貢献者が調査、実装、テスト、pull request 準備にかけるおおよその時間範囲です。
半日
活動状況Issue が今どれだけ取り組みやすいかを示します。新しい、活発、古い、ブロック中、またはメンテナー入力待ちなどです。
新着
明確さ期待される変更、受け入れ条件、次の手順がどれだけ明確かを示します。
明確
前提条件
Basic understanding of Python f stringsFamiliarity with Ruff's codebase
初心者向け度初回貢献者にどれだけ取り組みやすいかを 1-100 で推定したスコアです。
60