fix(pubsub): hide context.Cancelled error in sync pull (#3752)

pubsub/iterator.go

@@ -247,6 +247,8 @@ func (it *messageIterator) pullMessages(maxToPull int32) ([]*pb.ReceivedMessage,
 	switch {
 	case err == context.Canceled:
 		return nil, nil
+	case status.Code(err) == codes.Canceled:
+		return nil, nil
 	case err != nil:
 		return nil, err
 	default:

pubsub/iterator_test.go

@@ -400,3 +400,24 @@ func TestIterator_ModifyAckContextDeadline(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestIterator_SynchronousPullCancel(t *testing.T) {
+	srv := pstest.NewServer()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	srv.Publish(fullyQualifiedTopicName, []byte("creating a topic"), nil)
+
+	_, client, err := initConn(ctx, srv.Addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	iter := newMessageIterator(client.subc, fullyQualifiedTopicName, &pullOptions{})
+
+	// Cancelling the iterator and pulling should not result in any errors.
+	iter.cancel()
+
+	if _, err := iter.pullMessages(100); err != nil {
+		t.Fatalf("Got error in pullMessages: %v", err)
+	}
+}