Fix unstable formatting with comments on optional parens#5241
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cobaltt7 merged 3 commits intoJul 21, 2026
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Description
Fixes multi-pass instability when an inline comment sits on optional parentheses (assert message / assignment RHS). Omitting those parens re-parented the comment onto a different leaf, so the RHS splitter chose a different shape on the next pass and tripped the second-pass stability check.
can_omit_invisible_parensnow returns false when the optional opening paren already carries an inline comment, which pins the comment and keeps the formatting stable. Covers the #3701 reproducer and the same class from #3706 / #4384.Checklist - did you ...
--previewstyle, following thestability policy?
(N/A — this is an unstable-formatting bug fix, not a deliberate style change.)
CHANGES.mdif necessary?(N/A — unintended formatting bug; no style-guide rewrite.)
Fixes #3701