always pass handshakeInitializationPacket to ChangeUser

If the queue is empty before calling a ChangeUser sequence, the sequence will be started without being passed the handshake packet. This makes sure it gets passed.

Additionally, validateEnqueue now has a test that handeshake() was called before changeUser().

fixes mysqljs#374

Author: seanmonstar

lib/protocol/Protocol.js

@@ -106,25 +106,34 @@ Protocol.prototype._enqueue = function(sequence) {
 
   if (this._queue.length === 1) {
     this._parser.resetPacketNumber();
-    sequence.start();
+    if (sequence.constructor == Sequences.ChangeUser) {
+      sequence.start(this._handshakeInitializationPacket);
+    } else {
+      sequence.start();
+    }
   }
 
   return sequence;
 };
 
 Protocol.prototype._validateEnqueue = function(sequence) {
   var err;
-  var prefix = 'Cannot enqueue ' + sequence.constructor.name + ' after ';
+  var prefix = 'Cannot enqueue ' + sequence.constructor.name;
+  var prefixBefore = prefix + ' before ';
+  var prefixAfter = prefix + ' after ';
 
   if (this._quitSequence) {
-    err      = new Error(prefix + 'invoking quit.');
+    err      = new Error(prefixAfter + 'invoking quit.');
     err.code = 'PROTOCOL_ENQUEUE_AFTER_QUIT';
   } else if (this._destroyed) {
-    err      = new Error(prefix + 'being destroyed.');
+    err      = new Error(prefixAfter + 'being destroyed.');
     err.code = 'PROTOCOL_ENQUEUE_AFTER_DESTROY';
   } else if (this._handshakeSequence && sequence.constructor === Sequences.Handshake) {
-    err      = new Error(prefix + 'already enqueuing a Handshake.');
+    err      = new Error(prefixAfter + 'already enqueuing a Handshake.');
     err.code = 'PROTOCOL_ENQUEUE_HANDSHAKE_TWICE';
+  } else if (!this._handshakeSequence && sequence.constructor === Sequences.ChangeUser) {
+    err      = new Error(prefixBefore + 'a Handshake.');
+    err.code = 'PROTOCOL_ENQUEUE_BEFORE_HANDSHAKE';
   } else {
     return true;
   }

test/integration/connection/test-change-user-empty-queue.js

@@ -0,0 +1,20 @@
+var common     = require('../../common');
+var connection = common.createConnection();
+var assert     = require('assert');
+
+if (common.isTravis()) {
+  return console.log('skipping - travis mysql does not support this test');
+}
+
+connection.query('CREATE DATABASE ' + common.testDatabase, function(err) {
+  if (err && err.code !== 'ER_DB_CREATE_EXISTS') throw err;
+
+  // wait till protocol._queue is empty
+  setTimeout(function() {
+    connection.changeUser({database: common.testDatabase}, function(err) {
+      assert.ifError(err);
+    });
+
+    connection.end();
+  }, 2000);
+});