Reject multi-line f-string elements before Python 3.12#24355
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charliermarsh merged 2 commits intomainfrom Apr 5, 2026
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Reject multi-line f-string elements before Python 3.12#24355charliermarsh merged 2 commits intomainfrom
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crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap
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## Summary Right now these tests are dependent on input order, so changes in the underlying hash can lead to churn in the fixtures. See, e.g.: #24355 (comment).
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| let source = self.source[range].as_bytes(); | ||
| let has_line_break = |
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Given that this is a non-trivial amount of work, I suggest we gate the checks with an early "Is this <= 3.12?" check.
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This whole block is already gated by if !self.options.target_version.supports_pep_701() (which is "Is this <= 3.12?").
| let slash_position = TextSize::try_from(slash_position).unwrap(); | ||
| TextRange::at(range.start() + slash_position, '\\'.text_len()) | ||
| }) | ||
| .collect::<Vec<_>>(); |
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Use peekable here and for comment_ranges instead of collecting or even better, move the backslash and comment emitting code above the has_line_break check and use a single has_backslash_or_comment boolean that you set when there's any comment or backslash.
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## Summary See: #24355 (comment). Prior to Python 3.12, we need to avoid emitting formatted expressions that span multiple lines in non-triple quoted f-strings.
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Summary
Before Python 3.12, a replacement field in an f-string can span multiple lines only if the outer f-string is triple-quoted. This was relaxed in Python 3.12, but we weren't rejecting these as syntactically invalid on earlier versions.
Closes #24348.