Refactor lexer state management to use save/restore pattern#245
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…restore - Move ANplusBParser from per-call allocation in parse_nth_expression() to a field on SelectorParser, initialized once in the constructor. This avoids allocating a new Lexer for every :nth-child()/:nth-of-type() etc. encountered. - Replace the temporary `new Lexer()` in SelectorParser.parse_lang_identifiers() and AtRulePreludeParser.parse_feature_value() with lexer.save_position() / restore_position(). The saved LexerPosition object is a plain struct with no heap cost beyond the object itself, and avoids re-allocating a full Lexer + re-initializing its source reference for each :lang() argument range and each media-feature value range. https://claude.ai/code/session_01CQeKNnXidD5EQVJY4xBMMp
Bundle ReportChanges will increase total bundle size by 18 bytes (0.01%) ⬆️. This is within the configured threshold ✅ Detailed changes
Affected Assets, Files, and Routes:view changes for bundle: @projectwallace/css-parser-esmAssets Changed:
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #245 +/- ##
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- Coverage 93.15% 93.14% -0.01%
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Files 17 17
Lines 3038 3035 -3
Branches 845 845
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- Hits 2830 2827 -3
Misses 208 208 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Summary
Eliminates per-call
Lexerallocations in the hot paths ofSelectorParserandAtRulePreludeParser:ANplusBParserinparse_nth_expression()— was allocating a newANplusBParser(and therefore a newLexer) for every:nth-child(),:nth-of-type(), etc. encountered. Promoted to a field onSelectorParser, initialized once in the constructor.Lexerinparse_lang_identifiers()— replacednew Lexer()+ reference swap withlexer.save_position()/restore_position().Lexerinparse_feature_value()— same save/restore replacement.Benchmark results
Tested against
main(Bootstrap 273 KB, Tailwind 3.5 MB). ops/sec, higher is better.mainTokenizer-only benchmarks are unchanged (expected — these changes only affect the selector and prelude parsers).
https://claude.ai/code/session_01CQeKNnXidD5EQVJY4xBMMp