Task cache: a build with outDir under a tracked dir (e.g. Laravel public/build) never caches — emptyOutDir delete-probe counted as a read

[gsmeira]

Describe the bug

When a cached vp build task empties its output directory before writing (Vite's default emptyOutDir: true), Node's recursive remove probes each existing output file with openat(path, O_RDONLY|O_NOFOLLOW|O_CLOEXEC|O_DIRECTORY), which fails with ENOTDIR on a regular file and is followed by unlink. The task-cache fs tracker counts that failed O_RDONLY probe as a content read. Because the build then writes a fresh same-named file (a manifest, index.html, a copied static asset) to that path, the task is flagged as having both read and written it → modified its input → never cached.

This is the same class as the already-fixed #1187 / #1095 ("output files in input scope → task modifies its own input"). Those were fixed by excluding the default output dir from input tracking, which is why a default dist/ build caches fine today. The bug here is the residual case that exclusion does not reach: when outDir is a custom path nested under a directory that is itself tracked input — e.g. laravel-vite-plugin's build.outDir = 'public/build', nested under public/ whose static assets the build reads and copies — the delete-probe under that path is still counted, and the build is uncacheable.

Minimal standalone reproduction (no Laravel, no framework)

Public repo: https://github.com/gsmeira/vite-plus-cache-repro (pnpm install, then the steps below). Two sibling apps with identical source; only build.outDir differs:

// apps/control/vite.config.ts — default outDir → caches
export default defineConfig({
  build: { manifest: "manifest.json", emptyOutDir: true },          // outDir defaults to dist/
  run:   { tasks: { build: { command: "vp build", cache: true } } },
})

// apps/bug/vite.config.ts — outDir nested under the tracked public/
export default defineConfig({
  build: { outDir: "public/build", manifest: "manifest.json", emptyOutDir: true },
  run:   { tasks: { build: { command: "vp build", cache: true } } },
})

public/ is Vite's default publicDir; its static asset (public/robots.txt) is read and copied by the build, so the tracker treats public/ as input scope and public/build/ (the outDir) is nested inside it.

Run for each app (build #2 executes over build #1's output, which is what arms emptyOutDir's delete):

vp cache clean && vp run --filter <app> build   # build #1 — writes output
vp cache clean && vp run --filter <app> build   # build #2 — executes over prior output, repopulates cache
vp run --filter <app> build                     # build #3 — should be a cache hit
vp run --last-details

Observed on vite-plus 0.2.1:

App	outDir	build #3
control	dist/ (default)	100% cache hit
bug	public/build/	0% — Not cached: read and wrote '…/public/build/<file>'

The named file varies run to run (whichever stable-named output under public/build/ the tracker counts first — manifest.json, index.html, or a copied public/* asset); strace -f -e trace=%file confirms the manifest receives the identical probe:

lstat(".../public/build/manifest.json") = 0
openat(".../public/build/manifest.json", O_RDONLY|O_NOFOLLOW|O_CLOEXEC|O_DIRECTORY) = -1 ENOTDIR
unlink(".../public/build/manifest.json") = 0
# ...later, in a worker thread, the fresh write:
openat(".../public/build/manifest.json", O_WRONLY|O_CREAT|O_TRUNC) = 29

So the trigger is purely structural — a stable-named output written into an outDir nested under a tracked input dir — and is independent of Laravel; public/build is just the most common instance of that shape.

What actually fixes it (fix localized to input-side exclusion)

Tested on 0.2.1, website-laravel, building over prior output:

Task config	Result
baseline (the bug)	0% — read and wrote public/build/…
exclude the outDir from input: input: [{ auto: true }, "!public/build/**"]	✅ 100% cache hit
declare output: output: ["public/build/**"]	❌ 0% — read and wrote public/build/…

So the cure is input-side exclusion of the output dir, not output declaration. Two further non-invasive confirmations the delete-probe is the sole cause: with no prior output (rm -rf public/build first) the build caches; and build.emptyOutDir: false (no recursive delete → no probe) makes it cache.

Relationship to existing work

• Cache never hits for vp pack / vp build tasks (modified their inputs) #1187, Cache miss on repeated pack builds: task modifies its own input #1095 (closed/fixed): the same "task modifies its own input" class, fixed for the default output dir. This report is the uncovered case for a custom outDir nested under a tracked directory.
• feat: integrate vite-task runner-aware tools (auto output + tracked envs) #1774 (open, draft — "integrate vite-task runner-aware tools: auto output + tracked envs"): routes Vite's real inputs/outputs to the runner via ignoreInput/ignoreOutput. That ignoreInput channel is exactly the input-side exclusion shown above to fix this, so feat: integrate vite-task runner-aware tools (auto output + tracked envs) #1774 very likely resolves this — could a maintainer confirm whether it covers a custom outDir nested under a tracked dir (not just the default dist/)? If so this can ride on feat: integrate vite-task runner-aware tools (auto output + tracked envs) #1774; if not, the targeted fix below stands on its own.

Impact

Any cacheable build that empties an output directory located under a tracked path before writing stable-named files (Laravel public/build/manifest.json, SSR bootstrap/ssr/ssr-manifest.json, copied public assets) is spuriously uncacheable on every incremental rebuild where prior output exists — i.e. exactly the warm-cache case the task cache exists to accelerate. Fresh checkouts / CI (no prior output) are unaffected.

Environment: vp 0.1.12; vite-plus 0.2.1 (vite-plus-core 0.2.1, vite 8.0.16, rolldown 1.1.1); Linux. fs tracker = fspy.

Reproduction

https://github.com/gsmeira/vite-plus-cache-repro

Steps to reproduce

Public minimal repo (verified from a clean git clone + pnpm install --frozen-lockfile): two identical apps differing only in build.outDir — apps/control (dist/, caches 100%) vs apps/bug (public/build/, 0% — "read and wrote …/public/build/…").

pnpm install
# bug — never caches:
vp cache clean && vp run --filter bug build      # build #1 (writes output)
vp cache clean && vp run --filter bug build      # build #2 (executes over prior output, repopulates cache)
vp run --filter bug build && vp run --last-details   # -> 0%, "read and wrote …/public/build/…"
# control — caches (same steps, --filter control) -> 100% cache hit

System Info

$ vp --version
vp v0.1.12
Local vite-plus:
  vite-plus  v0.2.1
Tools:
  vite             v8.0.16
  rolldown         v1.1.1
  vitest           v4.1.8
  oxfmt            v0.55.0
  oxlint           v1.70.0
  tsdown           v0.22.3
Environment:
  Package manager  pnpm v11.8.0
  Node.js          v>=22.12.0 (engines.node)

$ vp env current
Environment:
  Version       24.17.0
  Source        engines.node
  Project Root  <repro root>

Used Package Manager

pnpm

Logs

Validations

• Read the Contributing Guidelines.
• Check that there isn't already an issue for the same bug.
• Confirm this is a Vite+ issue and not an upstream issue (Vite, Vitest, tsdown, Rolldown, or Oxc).
• The provided reproduction is a minimal reproducible example.