perf: cut filesystem calls in the dependency walk - #282
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Per dependency edge the walk did an existsSync through the candidate symlink (~150us on Windows), then lstat and realpath to collapse it, and the walker lstat'ed the result again for its identity. Measured at this repo's root: 2482 existsSync, 1244 lstat, and 779 realpath calls for 420 packages. - Probe candidates with readlink first (~37us): a symlink yields its target directly, a real directory fails with EINVAL and is checked once, a missing entry fails with ENOENT. - Memoize per scan: node_modules directory existence, candidate paths, and symlink targets. Fifty packages depending on semver now resolve its virtual-store target once. - Prime the identity cache with resolved directories so the walker skips their lstat. - Sort workspace patterns and package dirs by code unit instead of localeCompare, which initialized the ICU collator (~7ms) on every CLI run and depends on the process locale. Same repo root afterwards: 1382 existsSync, 465 lstat, 0 realpath; intent list ~500ms -> ~320ms, and ~180ms -> ~135ms in an npm project. Discovered packages and paths are unchanged.
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📝 WalkthroughWalkthroughDependency discovery now caches filesystem checks, resolves symlinks with fewer calls, primes known directory identities, and uses deterministic workspace sorting. Tests cover chained symlinks, dangling links, shared caches, and nested or hoisted resolution. ChangesDependency discovery optimization
Priority: ⬇️ Low Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Refactor Sequence Diagram(s)sequenceDiagram
participant scanForIntents
participant DependencyWalker
participant resolveDepDir
participant IntentFsCache
scanForIntents->>DependencyWalker: provide primeFsIdentity
DependencyWalker->>resolveDepDir: resolve dependency directory
resolveDepDir-->>DependencyWalker: return cached directory or null
DependencyWalker->>IntentFsCache: prime resolved directory identity
Merge Risk: 🟡 Moderate · up to Windows installations that use UNC-backed dependency symlinks can have valid dependencies reported as missing. Preserve the UNC root before merging. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 23.53% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 17 functions across 6 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches 💡 2📝 Generate docstrings 💡
🛠️ Fix failing CI checks 💡
🧪 Generate unit tests (beta)
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| Command | Status | Duration | Result |
|---|---|---|---|
nx affected --targets=test:eslint,test:sherif,t... |
❌ Failed | 31s | View ↗ |
nx run-many --targets=build |
✅ Succeeded | 3s | View ↗ |
☁️ Nx Cloud last updated this comment at 2026-09-12 02:16:55 UTC
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Inline comments:
In `@packages/intent/src/shared/utils.ts`:
- Line 434: Update the extended-length path handling around target so the
\\?\UNC\ prefix converts to the UNC root \\ before processing drive-letter
prefixes; retain the existing drive-path normalization and ensure UNC targets
remain absolute for resolve.
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📒 Files selected for processing (7)
.changeset/fewer-walk-syscalls.mdpackages/intent/src/discovery/fs-cache.tspackages/intent/src/discovery/scanner.tspackages/intent/src/discovery/walk.tspackages/intent/src/setup/workspace-patterns.tspackages/intent/src/shared/utils.tspackages/intent/tests/resolve-dep-dir.test.ts
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Summary
Follow-up to #276, #278, and #279. After the resolver rewrite, a CPU profile of
intent listat this repo's root was still dominated by raw filesystem calls: 2482existsSync, 1244lstat, and 779realpathfor 420 packages. Per-call costs on Windows explain why: a stat through a pnpm virtual-store symlink is ~150 µs,lstat~70 µs, nativerealpath~120 µs, whilereadlinkis ~37 µs.This PR changes how each dependency edge is resolved:
readlinkfirst. A symlink yields its target directly; a real directory (npm/Yarn hoisting) fails withEINVALand is checked once; a missing entry fails withENOENT. Windows junction targets with the\?\prefix are handled.createDepDirCache) fornode_modulesdirectory existence, candidate paths, and symlink targets. Fifty packages depending onsemverused to resolve andrealpathits store link fifty times; now the target is resolved once.resolveDepDirkeeps its two-argument public signature; the cache is an optional third parameter.lstat-ing them again.localeCompareinitialized the ICU collator (~7 ms) on every CLI run, and its order depends on the process locale; code-unit order is free and identical everywhere.Measurements (Windows, warm, import + run of
main(['list']))Syscalls at the repo root:
existsSync2482 → 1382,lstat1244 → 465,realpath779 → 0.list --jsonoutput is byte-identical before and after on the npm example, and the resolver test file gains symlink-chain, dangling-link, and shared-cache cases.Summary by CodeRabbit
Performance Improvements
Bug Fixes