Tracking: always reply with an array of keys.

src/pubsub.c

@@ -35,7 +35,11 @@ int clientSubscriptionsCount(client *c);
  * Pubsub client replies API
  *----------------------------------------------------------------------------*/
 
-/* Send a pubsub message of type "message" to the client. */
+/* Send a pubsub message of type "message" to the client.
+ * Normally 'msg' is a Redis object containing the string to send as
+ * message. However if the caller sets 'msg' as NULL, it will be able
+ * to send a special message (for instance an Array type) by using the
+ * addReply*() API family. */
 void addReplyPubsubMessage(client *c, robj *channel, robj *msg) {
     if (c->resp == 2)
         addReply(c,shared.mbulkhdr[3]);
@@ -43,7 +47,7 @@ void addReplyPubsubMessage(client *c, robj *channel, robj *msg) {
         addReplyPushLen(c,3);
     addReply(c,shared.messagebulk);
     addReplyBulk(c,channel);
-    addReplyBulk(c,msg);
+    if (msg) addReplyBulk(c,msg);
 }
 
 /* Send a pubsub message of type "pmessage" to the client. The difference

src/tracking.c

@@ -132,13 +132,16 @@ void sendTrackingMessage(client *c, char *keyname, size_t keylen) {
     if (c->resp > 2) {
         addReplyPushLen(c,2);
         addReplyBulkCBuffer(c,"invalidate",10);
+        addReplyArrayLen(c,1);
         addReplyBulkCBuffer(c,keyname,keylen);
     } else if (using_redirection && c->flags & CLIENT_PUBSUB) {
         /* We use a static object to speedup things, however we assume
          * that addReplyPubsubMessage() will not take a reference. */
         robj keyobj;
         initStaticStringObject(keyobj,keyname);
-        addReplyPubsubMessage(c,TrackingChannelName,&keyobj);
+        addReplyPubsubMessage(c,TrackingChannelName,NULL);
+        addReplyArrayLen(c,1);
+        addReplyBulk(c,&keyobj);
         serverAssert(keyobj.refcount == 1);
     }
 }