Fix preprocessor numeric literal parsing to avoid incorrect partial matches#8404
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Pull request overview
This PR fixes a bug in the preprocessor's numeric literal parsing that could cause expressions starting with numbers to be incorrectly parsed as pure numeric values.
Changes:
- Added a strict regex pattern (
NUMERIC_LITERAL) to match only pure numeric literals (integers and decimals) - Replaced
parseFloat()check with the new regex test to prevent partial string parsing - Added three test cases to verify expressions like
#if 3 == 3are correctly rejected rather than incorrectly evaluated
Reviewed changes
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| File | Description |
|---|---|
| src/core/preprocessor.js | Introduced NUMERIC_LITERAL regex and updated evaluateAtomicExpression() to use strict pattern matching instead of parseFloat() |
| test/core/preprocessor.test.mjs | Added edge case tests for numeric expressions with comparison operators that should evaluate to false |
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willeastcott
approved these changes
Jan 23, 2026
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Fixes an edge case where expressions starting with numbers could be incorrectly parsed as numeric literals.
Problem
The numeric literal check using
parseFloat(expr)could produce incorrect results for expressions containing comparison operators. For example,#if 3 == 3would be parsed asparseFloat("3 == 3")which returns3(parseFloat stops at the first non-numeric character), causing the expression to incorrectly evaluate to true.Solution
Use a strict regex (
/^\d+(?:\.\d+)?$/) that only matches pure numeric literals, ensuring expressions like3 == 3or0 != 1don't get incorrectly parsed as numbers.Test Plan
#if 3 == 3,#if 0 != 1,#if 5 > 3)