UP032 fix doesn’t account for underscores in decimal `int` literals

[dscorbett]

Summary

The fix for f-string (UP032) parenthesizes decimal int literals when necessary to avoid syntax errors, except for literals containing underscores. Example:

$ cat >up032.py <<'# EOF'
print("{.real}".format(1_2))
# EOF

$ python up032.py
12

$ ruff --isolated check up032.py --select UP032 --diff 2>&1 | grep error:
error: Fix introduced a syntax error. Reverting all changes.

Version

ruff 0.14.1 (2bffef5 2025-10-16)

[ntBre]

Looks like we'll need to refine this check:

ruff/crates/ruff_linter/src/rules/pyupgrade/rules/f_strings.rs

Line 164 in d109f48

) => text.chars().all(|c| c.is_ascii_digit()),

[TaKO8Ki]

I will take this one.