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[Pyflakes] F541 fix changes behavior if the string becomes a docstring #18807
Description
Summary
If the string f-string-missing-placeholders (F541) is targeting is in a position where it would become a docstring, it can change behavior. It should probably be marked unsafe or not apply in this case.
playground
PS ~\Desktop\New_folder\ruff>Get-Content issue.py
f"Hello, world!"
print(__doc__)PS ~\Desktop\New_folder\ruff>py issue.py
None
PS ~\Desktop\New_folder\ruff>uvx ruff check issue.py --isolated --select F
issue.py:1:1: F541 [*] f-string without any placeholders
|
1 | f"Hello, world!"
| ^^^^^^^^^^^^^^^^ F541
2 | print(__doc__)
|
= help: Remove extraneous `f` prefix
Found 1 error.
[*] 1 fixable with the `--fix` option.PS ~\Desktop\New_folder\ruff>uvx ruff check issue.py --isolated --select F --fix
Found 1 error (1 fixed, 0 remaining).
PS ~\Desktop\New_folder\ruff>Get-Content issue.py
"Hello, world!"
print(__doc__)PS ~\Desktop\New_folder\ruff>py issue.py
Hello, world!
Version
ruff 0.12.0 (87f0feb 2025-06-17) + playground
Activity
MichaReiser commentedon Jun 20, 2025
Thanks. I think we shouldn't provide a fix in this (rare) case
fix(pyflakes): suppress F541 autofix when removal would create a docs…
baltasarblanco commentedon Aug 26, 2026
Hi, how's it going @MichaReiser? I saw that a while ago you said we shouldn't offer a fix here. I'd like to ask for your opinion: I've been running some tests and noticed the scope is wider than what was originally reported; it's not just the module case — I've verified that function, class and implicit concatenation are also affected (
""f""becomes"" ""). I wanted to know whether you'd still prefer the earlier approach (not offering a fix) or degrading it to unsafe? I've already identified where a check could go. Looking forward to your reply, thanks!MichaReiser commentedon Aug 26, 2026
Either unsafe or not provide a fix seems fine to me. Yes, this applies to f-strings in all docstring positions, this also includes attribute docstrings
baltasarblanco commentedon Aug 26, 2026
Perfect, thank you! One more question: would you recommend covering only the reachable positions, avoiding touching the checker? Or would you accept a change to cover all of them? With that, I could cover module and attribute. Thanks again!
[`pyflakes`] Mark the fix as unsafe when it creates a docstring (`F54…