fix(math): reject currency patterns and cross-line matches in inline math - #447
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lepture merged 1 commit intoJun 16, 2026
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…math Fix three bugs in INLINE_MATH_PATTERN that cause false-positive inline math detection on currency values like $51,300: 1. Add (?!\$) after opening $ to reject $$ block delimiter starts 2. Change [^$\\] to [^$\\\n] to disallow newlines (single-line only) 3. Add (?!\d) after closing $ to reject currency (GFM-compatible) 4. Remove broken (?!\s) lookahead before closing $ (was always a no-op since it checked the $ delimiter itself, not preceding content) The (?!\s) at the opening is preserved — inline math still requires non-whitespace after the opening $. Reported-by: geopanther (geopanther/mdfluence#70)
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Branches 432 432
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Summary
Mistune's
INLINE_MATH_PATTERNhas bugs that cause false-positive inline math detection on currency values like$51,300. This PR fixes them directly in the upstream regex.Root Cause
Three issues in the current regex
\$(?!\s)(?P<math_text>(?:[^$\\]|\\.)+?)(?!\s)\$:(?!\s)checks the closing$delimiter (which is never whitespace), not the preceding content character. It's a no-op.[^$\\]allows newlines, so$signs on different lines can pair as math delimiters.$followed by a digit (e.g.$51,300) is accepted, matching currency as math.Additionally, no
(?!\$)guard prevents partial matching of$$block delimiters as inline math.Fix
New pattern:
\$(?!\$)(?!\s)(?P<math_text>(?:[^$\\\n]|\\.)+?)\$(?!\d)Changes:
(?!\$): reject$$block delimiter starts[^$\\\n]: disallow newlines in inline math (single-line only)(?!\d): closing$cannot precede a digit (GFM-compatible, rejects currency)(?!\s)before closing$(was always a no-op)Tests
New fixture test cases added covering:
$x^2$,$n$th, trailing punctuation$51,300pairs, single$1.6TAll 978 existing tests pass with no regressions.
Credit
Bug identified via geopanther/mdfluence#70.