Root cause of the flaky cache tests (TestServeHTTP_DirectoryListingsCachedAsSidecar
and the other hit-path tests, ~1-in-many under parallel load): on a cache
hit, ServeHTTP launches `go c.revalidate(...)` / `go c.revalidateListing(...)`,
which write into the cache root (MkdirAll + CreateTemp + Rename). Those
goroutines outlive the request — and in tests, the test — so they race
t.TempDir's RemoveAll cleanup, recreating the dir or dropping a temp file
mid-removal. testing then reports "TempDir RemoveAll cleanup: ... directory
not empty" and marks the test failed (with a 0.00s body, no assertion line).
It only surfaced under the full parallel suite / -count because the timing
has to collide.
Fix: track these background goroutines in a sync.WaitGroup via a goBackground
helper, and expose Wait(). newTestCache registers t.Cleanup(c.Wait) — cleanups
fire LIFO and t.TempDir registered its RemoveAll first, so the drain runs
before it (upstream Close was registered earliest, so it runs last and stays
up while goroutines finish). runClient also calls cacheLayer.Wait() after
srv.Shutdown so in-flight sidecar writes complete on graceful shutdown rather
than being abandoned.
Verified: cache package at -count=200 reliably failed before, passes clean
after (0 failures, 0 cleanup errors); full `go test ./...` + vet green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ZDDC
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