fix(mongo_client): translate options for connectWithUrl

Fixes NODE-1531

lib/operations/mongo_client_ops.js

@@ -296,16 +296,31 @@ function connectWithUrl(mongoClient, url, options, connectCallback) {
  // Propagate the events to the client
  relayEvents(mongoClient, url);
 
+ let finalOptions = Object.assign({}, options);
+
+ // If we have a readPreference passed in by the db options, convert it from a string
+ if (typeof options.readPreference === 'string' || typeof options.read_preference === 'string') {
+ finalOptions.readPreference = new ReadPreference(
+ options.readPreference || options.read_preference
+ );
+ }
+
  // Connect
  return url.connect(
- options,
- connectHandler(mongoClient, options, (err, topology) => {
+ finalOptions,
+ connectHandler(mongoClient, finalOptions, (err, topology) => {
  if (err) return connectCallback(err, topology);
- if (options.user || options.password || options.authMechanism) {
- return authenticate(mongoClient, options.user, options.password, options, err => {
- if (err) return connectCallback(err, topology);
- connectCallback(err, topology);
- });
+ if (finalOptions.user || finalOptions.password || finalOptions.authMechanism) {
+ return authenticate(
+ mongoClient,
+ finalOptions.user,
+ finalOptions.password,
+ finalOptions,
+ err => {
+ if (err) return connectCallback(err, topology);
+ connectCallback(err, topology);
+ }
+ );
  }
 
  connectCallback(err, topology);