gh-137314: Fix incorrect treatment of format specs in raw fstrings

[pablogsal]

• Issue: Raw f-string format spec undocumented behavior change between 3.11 and 3.12 #137314

[pablogsal]

@Yhg1s should we backport this to 3.12? is not a security fix certianly so my default would be 'no' but my guess is that it will make maintaining linterns a pain in this area if the behaviour is different.

[serhiy-storchaka]

LGTM. 👍

[miss-islington-app]

Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-137344 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-137345 is a backport of this pull request to the 3.13 branch.

[Yhg1s]

@Yhg1s should we backport this to 3.12? is not a security fix certianly so my default would be 'no' but my guess is that it will make maintaining linterns a pain in this area if the behaviour is different.

Linters will probably have to consider earlier 3.12 releases anyway (at least on Windows and probably macOS, since we won't be building installers with this fix), and yeah, it's not a security fix. I don't see a particular compelling reason to backport it unless we want to reconsider the whole security-fix-only idea.

[dylwil3]

@Yhg1s should we backport this to 3.12? is not a security fix certianly so my default would be 'no' but my guess is that it will make maintaining linterns a pain in this area if the behaviour is different.

Linters will probably have to consider earlier 3.12 releases anyway (at least on Windows and probably macOS, since we won't be building installers with this fix), and yeah, it's not a security fix. I don't see a particular compelling reason to backport it unless we want to reconsider the whole security-fix-only idea.

Happy to special case, but just for clarification this was a regression in 3.12, not something that held in 3.11 - so the behavior in the linter would not be "3.12 and earlier do this..." but rather "only for 3.12 do this".

[picnixz]

What we meant by earlier releases is the patch version. We only release sources for security-only branches, and usually it's only Linux distributions that pick them up to so that users can upgrade their system-wide installation from their package manager. So Windows is likely to have Python 3.12.N without the fix while Linux would have the fix in 3.12.(N+1).