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>

2 files changed, 36 insertions, 2 deletions

diff --git a/cmd/hakurei/testsuite/sandbox/tester/main.go b/cmd/hakurei/testsuite/sandbox/tester/main.go
index 452712d9..6ccad5be 100644
--- a/cmd/hakurei/testsuite/sandbox/tester/main.go
+++ b/cmd/hakurei/testsuite/sandbox/tester/main.go
@@ -15,6 +15,7 @@ import (
 	"syscall"
 
 	"hakurei.app/cmd/hakurei/testsuite/sandbox/testdata"
+	"hakurei.app/internal/testsuite"
 	"hakurei.app/internal/testsuite/mountinfo"
 )
 
@@ -29,6 +30,13 @@ func mustAbs(s string) string {
 	return s
 }
 
+// dial is [net.Dial] retrying intermittent EACCES.
+func dial(network, address string) (net.Conn, error) {
+	return testsuite.RetryExp(func() (net.Conn, error) {
+		return net.Dial(network, address)
+	}, syscall.EACCES)
+}
+
 func main() {
 	log.SetFlags(0)
 	log.SetPrefix("tester: ")
@@ -165,8 +173,8 @@ func main() {
 
 	if want.TrySocket != "" {
 	retry:
-		abstractConn, abstractErr := net.Dial("unix", "@"+want.TrySocket)
-		pathnameConn, pathnameErr := net.Dial("unix", want.TrySocket)
+		abstractConn, abstractErr := dial("unix", "@"+want.TrySocket)
+		pathnameConn, pathnameErr := dial("unix", want.TrySocket)
 		ok := true
 
 		if abstractErr == nil {
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)