Fix panic on publish before RetryClient.SetClient (#158)

retryclient.go

@@ -52,9 +52,12 @@ func (c *RetryClient) Publish(ctx context.Context, message *Message) error {
 	cli := c.cli
 	c.mu.Unlock()
 
-	if err := cli.ValidateMessage(message); err != nil {
-		return wrapError(err, "validating publishing message")
+	if cli != nil {
+		if err := cli.ValidateMessage(message); err != nil {
+			return wrapError(err, "validating publishing message")
+		}
 	}
+
 	return wrapError(c.pushTask(ctx, func(ctx context.Context, cli *BaseClient) {
 		c.publish(ctx, cli, message)
 	}), "retryclient: publishing")
@@ -78,6 +81,9 @@ func (c *RetryClient) Unsubscribe(ctx context.Context, topics ...string) error {
 }
 
 func (c *RetryClient) publish(ctx context.Context, cli *BaseClient, message *Message) {
+	if err := cli.ValidateMessage(message); err != nil {
+		return
+	}
 	publish := func(ctx context.Context, cli *BaseClient, message *Message) {
 		if err := cli.Publish(ctx, message); err != nil {
 			select {

retryclient_test.go

@@ -34,3 +34,27 @@ func TestRetryClientPublish_MessageValidationError(t *testing.T) {
 		)
 	}
 }
+
+func TestRetryClient_NilClient(t *testing.T) {
+	cli := &RetryClient{}
+	t.Run("Publish", func(t *testing.T) {
+		if err := cli.Publish(context.Background(), &Message{
+			Payload: make([]byte, 101),
+		}); err != nil {
+			t.Errorf("Unexpected error: '%v'", err)
+		}
+	})
+	t.Run("Subscribe", func(t *testing.T) {
+		if _, err := cli.Subscribe(context.Background(), Subscription{
+			Topic: "test",
+			QoS:   QoS1,
+		}); err != nil {
+			t.Errorf("Unexpected error: '%v'", err)
+		}
+	})
+	t.Run("Unsubscribe", func(t *testing.T) {
+		if err := cli.Unsubscribe(context.Background(), "test"); err != nil {
+			t.Errorf("Unexpected error: '%v'", err)
+		}
+	})
+}