Backport useMongoClient option to 4.6.8 (#1)

Backport `useMongoClient` option to `4.6.8`

Originally introduced in: Automattic#5355

Then updated with latest changes from `4.13.21`:

 - https://github.com/Automattic/mongoose/blame/4.13.21/lib/connection.js
 - https://github.com/Automattic/mongoose/blame/4.13.21/lib/index.js
 - https://github.com/Automattic/mongoose/blame/4.13.21/test/connection.test.js
 - https://github.com/Automattic/mongoose/blob/4.13.21/test/common.js


New tests passing:
```sh
$ npm run mocha -- test/connection.test.js
[...]
71 passing (15s)
```

.gitignore

@@ -18,6 +18,7 @@ test/triage/*.js
 bin/mongoose.min.js
 coverage
 npm-debug.log
+data/
 
 # Visual Studio
 # =========

lib/connection.js

@@ -11,6 +11,7 @@ var STATES = require('./connectionstate');
 var MongooseError = require('./error');
 var muri = require('muri');
 var PromiseProvider = require('./promise_provider');
+var mongodb = require('mongodb');
 
 /*!
  * Protocol prefix regexp.
@@ -64,6 +65,7 @@ function Connection(base) {
   this.name = null;
   this.options = null;
   this.otherDbs = [];
+  this.states = STATES;
   this._readyState = STATES.disconnected;
   this._closeCalled = false;
   this._hasOpened = false;
@@ -578,6 +580,130 @@ Connection.prototype.onOpen = function(callback) {
   }
 };
 
+/**
+ * Opens the connection with a URI using `MongoClient.connect()`.
+ *
+ * @param {String} uri The URI to connect with.
+ * @param {Object} [options] Passed on to http://mongodb.github.io/node-mongodb-native/2.2/api/MongoClient.html#connect
+ * @param {Function} [callback]
+ * @returns {Connection} this
+ * @api private
+ */
+
+Connection.prototype.openUri = function(uri, options, callback) {
+  this.readyState = STATES.connecting;
+  this._closeCalled = false;
+
+  try {
+    var parsed = muri(uri);
+    this.name = parsed.db;
+    this.host = parsed.hosts[0].host || parsed.hosts[0].ipc;
+    this.port = parsed.hosts[0].port || 27017;
+    if (parsed.auth) {
+      this.user = parsed.auth.user;
+      this.pass = parsed.auth.pass;
+    }
+  } catch (error) {
+    this.error(error, callback);
+    throw error;
+  }
+
+  if (typeof options === 'function') {
+    callback = options;
+    options = null;
+  }
+
+  var Promise = PromiseProvider.get();
+  var _this = this;
+
+  if (options) {
+    options = utils.clone(options, { retainKeyOrder: true });
+    delete options.useMongoClient;
+    var autoIndex = options.config && options.config.autoIndex != null ?
+      options.config.autoIndex :
+      options.autoIndex;
+    if (autoIndex != null) {
+      this.config.autoIndex = autoIndex !== false;
+      delete options.config;
+      delete options.autoIndex;
+    }
+
+    // Backwards compat
+    if (options.user || options.pass) {
+      options.auth = options.auth || {};
+      options.auth.user = options.user;
+      options.auth.password = options.pass;
+      delete options.user;
+      delete options.pass;
+      this.user = options.auth.user;
+      this.pass = options.auth.password;
+    }
+
+    if (options.bufferCommands != null) {
+      throw new Error('options.bufferCommands not supported on this custom fork of mongoose for Gitter');
+      // options.bufferMaxEntries = 0;
+      // this.config.bufferCommands = options.bufferCommands;
+      // delete options.bufferCommands;
+    }
+  }
+
+  this._connectionOptions = options;
+
+  var promise = new Promise.ES6(function(resolve, reject) {
+    mongodb.MongoClient.connect(uri, options, function(error, db) {
+      if (error) {
+        _this.readyState = STATES.disconnected;
+        if (_this.listeners('error').length) {
+          _this.emit('error', error);
+        }
+        callback && callback(error);
+        return reject(error);
+      }
+      // Backwards compat for mongoose 4.x
+      db.on('reconnect', function() {
+        _this.readyState = STATES.connected;
+        _this.emit('reconnect');
+        _this.emit('reconnected');
+      });
+      db.s.topology.on('reconnectFailed', function() {
+        _this.emit('reconnectFailed');
+      });
+      db.s.topology.on('close', function() {
+        // Implicitly emits 'disconnected'
+        _this.readyState = STATES.disconnected;
+      });
+      db.on('timeout', function() {
+        _this.emit('timeout');
+      });
+
+      delete _this.then;
+      delete _this.catch;
+
+      _this.db = db;
+      _this.readyState = STATES.connected;
+
+      for (var i in _this.collections) {
+        if (utils.object.hasOwnProperty(_this.collections, i)) {
+          _this.collections[i].onOpen();
+        }
+      }
+
+      callback && callback(null, _this);
+      resolve(_this);
+      _this.emit('open');
+    });
+  });
+
+  this.then = function(resolve, reject) {
+    return promise.then(resolve, reject);
+  };
+  this.catch = function(reject) {
+    return promise.catch(reject);
+  };
+
+  return this;
+};
+
 /**
  * Closes the connection
  *

lib/index.js

@@ -170,7 +170,7 @@ var checkReplicaSetInUri = function(uri) {
  * @param {Boolean} [options.config.autoIndex] set to false to disable automatic index creation for all models associated with this connection.
  * @see Connection#open #connection_Connection-open
  * @see Connection#openSet #connection_Connection-openSet
- * @return {Connection} the created Connection object
+ * @return {Connection|Promise} the created Connection object, or promise that resolves to the connection if `useMongoClient` option specified.
  * @api public
  */
 
@@ -179,6 +179,11 @@ Mongoose.prototype.createConnection = function(uri, options) {
   this.connections.push(conn);
 
   var rsOption = options && (options.replset || options.replSet);
+
+  if (options && options.useMongoClient) {
+    return conn.openUri(uri, options);
+  }
+
   if (arguments.length) {
     if (rgxReplSet.test(arguments[0]) || checkReplicaSetInUri(arguments[0])) {
       conn.openSet.apply(conn, arguments);
@@ -227,6 +232,7 @@ Mongoose.prototype.createConnection.$hasSideEffects = true;
  *
  * @param {String} uri(s)
  * @param {Object} [options]
+ * @param {Boolean} [options.useMongoClient] false by default, set to true to use new mongoose connection logic
  * @param {Function} [callback]
  * @see Mongoose#createConnection #index_Mongoose-createConnection
  * @api public
@@ -235,6 +241,13 @@ Mongoose.prototype.createConnection.$hasSideEffects = true;
 
 Mongoose.prototype.connect = function() {
   var conn = this.connection;
+
+  if ((arguments.length === 2 || arguments.length === 3) &&
+      typeof arguments[0] === 'string' &&
+      typeof arguments[1] === 'object' &&
+      arguments[1].useMongoClient === true) {
+    return conn.openUri(arguments[0], arguments[1], arguments[2]);
+  }
   if (rgxReplSet.test(arguments[0]) || checkReplicaSetInUri(arguments[0])) {
     return new MongooseThenable(this, conn.openSet.apply(conn, arguments));
   }

package.json

@@ -46,6 +46,7 @@
     "markdown": "0.3.1",
     "marked": "0.3.6",
     "mocha": "3.1.2",
+    "mongodb-topology-manager": "^1.0.11",
     "mongoose-long": "0.1.1",
     "node-static": "0.7.7",
     "power-assert": "1.4.1",
@@ -72,7 +73,8 @@
     "install-browser": "npm install `node format_deps.js`",
     "test": "mocha test/*.test.js test/**/*.test.js",
     "posttest": "eslint . --quiet",
-    "test-cov": "istanbul cover --report text --report html _mocha test/*.test.js"
+    "test-cov": "istanbul cover --report text --report html _mocha test/*.test.js",
+    "mocha": "mocha"
   },
   "main": "./index.js",
   "engines": {

test/common.js

@@ -4,13 +4,16 @@
 
 Error.stackTraceLimit = 10;
 
+var Server = require('mongodb-topology-manager').Server;
 var mongoose = require('../'),
     Collection = mongoose.Collection,
     assert = require('power-assert'),
     queryCount = 0,
     opened = 0,
     closed = 0;
 
+var server;
+
 if (process.env.D === '1') {
   mongoose.set('debug', true);
 }
@@ -156,13 +159,23 @@ function dropDBs(done) {
   });
 }
 
+before(function() {
+  return server.purge();
+});
+
+after(function() {
+  this.timeout(15000);
+
+  return server.stop();
+});
+
 before(function(done) {
   this.timeout(10 * 1000);
   dropDBs(done);
 });
-after(function(done) {
-  // DropDBs can be extraordinarily slow on 3.2
-  //this.timeout(120 * 1000);
-  //dropDBs(done);
-  done();
+
+module.exports.server = server = new Server('mongod', {
+  port: 27000,
+  dbpath: './data/db/27000',
+  storageEngine: 'mmapv1'
 });