Speed up first incremental rebuilds after shared dependency edits - #64469
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The export-to-module index is now built directly from each module's export table and published with a completion flag, so a lookup that re-enters during the build falls back to the per-file scan instead of building the index again. Per-module export buckets are sorted once when created rather than on every lookup. With dependent signatures computed in parallel, another changed file's traversal can compute a changed file's signature first. The cached path of updateShapeSignature now reports whether the signature changed, so a changed file that affects global scope still invalidates every file. The incremental scenario moves into the TestTscIncremental table and also runs under --watch. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Fixes #64464
A comment-only edit to a widely imported module makes the first incremental rebuild far slower than a full check, even with
noEmit. Two things cost the time. While emitting declaration signatures, the checker found the modules that can re-export a symbol by scanning every module's exports for every lookup. And the incremental builder computed the signatures of dependent files one file at a time.The checker now keeps one index from a resolved export target to the modules exporting it, built on first use, plus a per-module cache of exports by target. The builder computes dependent signatures in parallel. On the issue's 6,000-leaf reproducer the first rebuild after the comment edit drops from 40.9 s to 1.5 s, with a byte-identical tsbuildinfo; peak RSS on that rebuild rises from 379 MiB to 501 MiB. Clean and second rebuilds are unchanged.
Two decisions worth a look. With parallel traversal, a changed file's signature may already have been computed by another changed file's traversal, so the cached-result path in
updateShapeSignaturenow reports whether the signature actually changed instead of always false; otherwise a changed file that also affects global scope would no longer invalidate every file. Strada returns false there, but it is sequential and never hits this case. A unit test covers it. The checker index is published before it is filled, with a completion flag: a lookup that re-enters while the index is being built falls back to the old per-file scan rather than building it twice. No runtime path was found that triggers this; it is a guard.Most of this change was generated with AI tooling; I have hit this problem myself and have reviewed the result.
🤖 Generated with Claude Code