namespace: improve middleware logic

lib/namespace.js

@@ -134,11 +134,23 @@ Namespace.prototype.add = function(client, fn){
   var socket = new Socket(this, client);
   var self = this;
   this.run(socket, function(err){
-    if (err) return socket.err(err.data || err.message);
-    self.sockets.push(socket);
-    self.emit('connect', socket);
-    self.emit('connection', socket);
-    socket.onconnect();
+    process.nextTick(function(){
+      if (err) return socket.err(err.data || err.message);
+
+      // track socket
+      self.sockets.push(socket);
+
+      // it's paramount that the internal `onconnect` logic
+      // fires before user-set events to prevent state order
+      // violations (such as a disconnection before the connection
+      // logic is complete)
+      socket.onconnect();
+      if (fn) fn();
+
+      // fire user-set events
+      self.emit('connect', socket);
+      self.emit('connection', socket);
+    });
   });
   return socket;
 };