perf: defer source map generation until first access#2962
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MathiasWP wants to merge 3 commits intosveltejs:masterfrom
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perf: defer source map generation until first access#2962MathiasWP wants to merge 3 commits intosveltejs:masterfrom
MathiasWP wants to merge 3 commits intosveltejs:masterfrom
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generateMap({ hires: true }) accounts for ~10% of svelte2tsx time.
Most consumers (language server getText/getLength/getChangeRange,
svelte-check incremental mode) never need the source map, so deferring
generation to a lazy getter avoids this cost on the hot path.
The map is cached on first access via Object.defineProperty so
subsequent reads don't regenerate.
Benchmarks (300-line component):
- Without .map access: 4.5ms (10% faster)
- With .map access: 5.0ms (unchanged)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
🦋 Changeset detectedLatest commit: a1b3c06 The changes in this PR will be included in the next version bump. This PR includes changesets to release 3 packages
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Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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This won't make any difference. The map property is accessed immediately. |
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Summary
generateMap({ hires: true })accounts for ~10% ofsvelte2tsxwall-clock timegetText(),getLength(),getChangeRange()don't use the map. The mapper is already lazily initialized, but the map object itself was eagerly computed..code, never.mapmapproperty is now a lazy getter that callsgenerateMap()on first access and caches the result viaObject.defineProperty.map(TypeScript plugin, sourcemap tests) see no regression — the map is generated once on first accessBenchmarks
Measured with realistic generated Svelte components of various sizes:
.mapaccess.mapaccessTest plan
🤖 Generated with Claude Code