skipping pushing message to client if there are no messages; fixes flaky test and de-intensifies read loop

deltas.go

@@ -92,8 +92,9 @@ func (ch *CaddyHugo) handleConn(conn DeltaConn, doc *docref) (int, error) {
 	wroteMessagesCh := make(chan Message, 2)
 
 	client := doc.doc.Client(acedoc.DeltaHandlerFunc(func(ds []acedoc.Delta) error {
-		wroteMessagesCh <- Message{Deltas: ds}
-		return conn.WriteJSON(ch.Message(ds...))
+		m := ch.Message(ds...)
+		wroteMessagesCh <- m
+		return conn.WriteJSON(m)
 	}))
 
 	ch.mtx.Lock()
@@ -119,6 +120,11 @@ func (ch *CaddyHugo) handleConn(conn DeltaConn, doc *docref) (int, error) {
 			}
 			ch.ObserveLTime(message.LTime)
 
+			if len(message.Deltas) == 0 {
+				time.Sleep(10 * time.Microsecond)
+				continue
+			}
+
 			err = client.PushDeltas(message.Deltas...)
 			if err != nil {
 				errCh <- err

doc_test.go

@@ -233,7 +233,7 @@ func TestDeltasDouble(t *testing.T) {
 	// send the second message, via clientB
 	clientB.ReceiveJSON(w.CH.Message(acedoc.Insert(0, 0, "b")))
 
-	time.Sleep(200 * time.Millisecond)
+	time.Sleep(400 * time.Millisecond)
 
 	clientA.mtx.Lock()
 	clientB.mtx.Lock()