🐛 Prevent caching presence broadcasts rejected by middleware

The `Agent` stores the most recent presence broadcast sent by a client.
However, it eagerly stores this before running the `receivePresence`
middleware, which may actually decide that the presence broadcast is
invalid (eg malformed, unauthorized, etc.).

This means that the latest cached presence state may not be "legal".

This change moves the caching inside the `trigger()` call, so we only
store presence values that have "passed" the middleware.

lib/agent.js

@@ -769,18 +769,19 @@ Agent.prototype._src = function() {
 Agent.prototype._broadcastPresence = function(presence, callback) {
   var agent = this;
   var backend = this.backend;
-  var requests = this.presenceRequests[presence.ch] || (this.presenceRequests[presence.ch] = {});
-  var previousRequest = requests[presence.id];
-  if (!previousRequest || previousRequest.pv < presence.pv) {
-    this.presenceRequests[presence.ch][presence.id] = presence;
-  }
+  var presenceRequests = this.presenceRequests;
   var context = {
     presence: presence,
     collection: presence.c
   };
   var start = Date.now();
   backend.trigger(backend.MIDDLEWARE_ACTIONS.receivePresence, this, context, function(error) {
     if (error) return callback(error);
+    var requests = presenceRequests[presence.ch] || (presenceRequests[presence.ch] = {});
+    var previousRequest = requests[presence.id];
+    if (!previousRequest || previousRequest.pv < presence.pv) {
+      presenceRequests[presence.ch][presence.id] = presence;
+    }
     backend.transformPresenceToLatestVersion(agent, presence, function(error, presence) {
       if (error) return callback(error);
       var channel = agent._getPresenceChannel(presence.ch);

test/client/presence/presence.js

@@ -659,6 +659,7 @@ describe('Presence', function() {
           function(next) {
             presence2.on('receive', function(id, value) {
               expect(value).to.eql({index: 6});
+              expect(connection1.agent.presenceRequests['test-channel']['presence-1'].p).to.eql({index: 6});
               next();
             });
             localPresence1.submit({index: 5}, errorHandler(done));
@@ -681,6 +682,7 @@ describe('Presence', function() {
             });
             localPresence1.submit({index: 5}, function(error) {
               expect(error.message).to.contain('bad!');
+              expect(connection1.agent.presenceRequests['test-channel']).not.to.be.ok;
               next();
             });
           }