internal/testsuite: handle intermittent EACCES

The test suite is now fast enough that the tester can also suffer from
the same vfs race. This change works around such intermittent failures.

Signed-off-by: Ophestra <cat@gensokyo.uk>

1 files changed, 26 insertions, 0 deletions

diff --git a/internal/testsuite/testsuite.go b/internal/testsuite/testsuite.go
index 6e48eca1..a1e39720 100644
--- a/internal/testsuite/testsuite.go
+++ b/internal/testsuite/testsuite.go
@@ -28,6 +28,32 @@ func ReceiveSignals() {
 	log.Fatalf("terminating on signal %s", <-s)
 }
 
+// RetryExp retries f if the resulting error is equivalent to e according to
+// [errors.Is], up to 8 times.
+func RetryExp[T any](f func() (T, error), e error) (v T, err error) {
+	const statRetry = 8 // 64 ms
+	var n int
+	d := 256 * time.Microsecond
+
+retry:
+	v, err = f()
+	if err != nil {
+		if !errors.Is(err, e) {
+			return
+		}
+
+		n++
+		if n == statRetry {
+			return
+		}
+
+		time.Sleep(d)
+		d *= 2
+		goto retry
+	}
+	return
+}
+
 var (
 	// users caches [user.LookupId] calls.
 	users = make(map[string]*user.User)