event: handle empty subscription list in JoinSubscriptions

event/multisub.go

@@ -19,6 +19,13 @@ package event
 // JoinSubscriptions joins multiple subscriptions to be able to track them as
 // one entity and collectively cancel them or consume any errors from them.
 func JoinSubscriptions(subs ...Subscription) Subscription {
+	// Handle empty subscription list to avoid blocking forever
+	if len(subs) == 0 {
+		return NewSubscription(func(unsubbed <-chan struct{}) error {
+			<-unsubbed
+			return nil
+		})
+	}
 	return NewSubscription(func(unsubbed <-chan struct{}) error {
 		// Unsubscribe all subscriptions before returning
 		defer func() {

event/multisub_test.go

@@ -173,3 +173,30 @@ func TestMultisubFullUnsubscribe(t *testing.T) {
 	default:
 	}
 }
+
+func TestMultisubEmpty(t *testing.T) {
+	// Test that joining zero subscriptions doesn't block forever
+	sub := JoinSubscriptions()
+	if sub == nil {
+		t.Fatal("JoinSubscriptions() returned nil")
+	}
+	// Should be able to unsubscribe immediately without blocking
+	done := make(chan struct{})
+	go func() {
+		sub.Unsubscribe()
+		close(done)
+	}()
+	select {
+	case <-done:
+		// Success - unsubscribe completed
+	case <-time.After(100 * time.Millisecond):
+		t.Error("Unsubscribe blocked on empty subscription list")
+	}
+	// Error channel should be closed
+	select {
+	case <-sub.Err():
+		// Expected - channel is closed
+	default:
+		t.Error("error channel not closed after unsubscribe")
+	}
+}