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fix(math): reject currency patterns and cross-line matches in inline 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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‎src/mistune/plugins/math.py‎

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__all__ = ["math", "math_in_quote", "math_in_list"]
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BLOCK_MATH_PATTERN = r"^ {0,3}\$\$[ \t]*\n(?P<math_text>[\s\S]+?)\n\$\$[ \t]*$"
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INLINE_MATH_PATTERN = r"\$(?!\s)(?P<math_text>(?:[^$\\]|\\.)+?)(?!\s)\$"
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INLINE_MATH_PATTERN = r"\$(?!\$)(?!\s)(?P<math_text>(?:[^$\\\n]|\\.)+?)\$(?!\d)"
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def parse_block_math(block: "BlockParser", m: Match[str], state: "BlockState") -> int:

‎tests/fixtures/math.txt‎

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@@ -61,3 +61,39 @@ Escaped dollar sign in math: $x=\$$
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<p>Escaped dollar sign in math: <span class="math">\(x=\$\)</span></p>
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````````````````````````````````
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```````````````````````````````` example
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The $n$th element is valid.
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.
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<p>The <span class="math">\(n\)</span>th element is valid.</p>
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````````````````````````````````
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```````````````````````````````` example
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Result is $x^2$.
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.
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<p>Result is <span class="math">\(x^2\)</span>.</p>
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````````````````````````````````
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## Currency rejection
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```````````````````````````````` example
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Price is $51,300 and cost is $51,300 total.
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.
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<p>Price is $51,300 and cost is $51,300 total.</p>
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````````````````````````````````
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```````````````````````````````` example
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The $1.6T valuation narrative.
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.
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<p>The $1.6T valuation narrative.</p>
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````````````````````````````````
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## Cross-line rejection
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```````````````````````````````` example
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Line one $500
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Line two $600
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.
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<p>Line one $500
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Line two $600</p>
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````````````````````````````````

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