History

Mathias Picker 0965028d3b perf: optimize CSS selector pruning (#17846 ) ## Summary Reduces CSS selector pruning overhead by eliminating unnecessary allocations and redundant work in the hot path. Changes: - Replace `.slice()` + `.shift()`/`.pop()` in `apply_selector` with index-based `from`/`to` params — avoids O(n) array copies per recursive call - Merge `has_selectors`/`other_selectors` split in `relative_selector_might_apply_to_node` into a single pass — eliminates 2 temporary array allocations per call - Hoist `name.toLowerCase()` out of the inner loop in `attribute_matches` - Replace `value.split(/\s/).includes()` with `indexOf` + boundary checks in `test_attribute` for `~=` — avoids array allocation on every class match - Skip `name.replace()` regex when selector name has no backslash ## Benchmark Interleaved benchmark (5 rounds, alternating baseline/optimized): ``` --- Round 1 --- Baseline: min=59.58ms median=64.63ms Optimized: min=47.20ms median=54.35ms --- Round 2 --- Baseline: min=59.11ms median=64.90ms Optimized: min=48.36ms median=54.74ms --- Round 3 --- Baseline: min=58.38ms median=64.06ms Optimized: min=48.38ms median=53.83ms --- Round 4 --- Baseline: min=58.49ms median=63.99ms Optimized: min=48.45ms median=53.82ms --- Round 5 --- Baseline: min=58.40ms median=64.07ms Optimized: min=48.97ms median=54.64ms Best min: Before=58.38ms After=47.20ms Improvement=19.1% Best median: Before=63.99ms After=53.82ms Improvement=15.9% ``` CPU profile before → after: \| Function \| Before \| After \| \|---\|---\|---\| \| `relative_selector_might_apply_to_node` \| 14.3% \| 5.2% \| \| `attribute_matches` \| 4.0% \| 3.3% \| \| `test_attribute` \| 3.2% \| <0.9% \| ## Test plan - [x] All 196 CSS tests pass (180 samples + 16 parse) - [x] All 31 snapshot tests pass - [x] All 2380 runtime-runes tests pass - [x] All 3291 runtime-legacy tests pass - [x] All 145 compiler-errors tests pass - [x] All 326 validator tests pass - [x] Added `css-prune-edge-cases` test covering: `~=` word matching (substring vs whole word), deep combinator chains (4+ levels), `:has()` combined with class selectors, escaped selectors, `:is()`/`:where()`/`:not()` with combinators - [x] Edge case test passes on both baseline and optimized code 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com> Co-authored-by: Rich Harris <rich.harris@vercel.com>		6 months ago
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README.md	…
breezy-jokes-laugh.md	fix: correctly add `__svelte_meta` after else-if chains (#17830 )	6 months ago
calm-clouds-wave.md	perf: cache element interactivity and source line splitting (#17839 )	6 months ago
config.json	…
curvy-stars-drop.md	chore: avoid reschedule during branch commit (#17837 )	6 months ago
fast-css-prune.md	perf: optimize CSS selector pruning (#17846 )	6 months ago
smooth-pens-jump.md	perf: avoid O(n²) name scanning in scope generate/unique (#17844 )	6 months ago
spicy-teeth-tan.md	fix: preserve each items that are needed by pending batches (#17819 )	6 months ago

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