Fields projection fix (#436)

* mongodb find, use fields in projection

* eliminate unnecessary calls during data map

* update filter.fields unit test to avoid juggler

Author: Gonyoda

lib/mongodb.js

@@ -1106,7 +1106,9 @@ MongoDB.prototype.all = function all(model, filter, options, callback) {
   fields = self.fromPropertyToDatabaseNames(model, fields);
 
   if (fields) {
-    this.execute(model, 'find', query, fields, processResponse);
+    // convert the array of fields into a projection object see http://mongodb.github.io/node-mongodb-native/3.0/api/Collection.html#find
+    var findOpts = { projection: fields };
+    this.execute(model, 'find', query, findOpts, processResponse);
   } else {
     this.execute(model, 'find', query, processResponse);
   }
@@ -1130,6 +1132,10 @@ MongoDB.prototype.all = function all(model, filter, options, callback) {
     } else if (filter.offset) {
       cursor.skip(filter.offset);
     }
+
+    var shouldSetIdValue = idIncluded(fields, idName);
+    var deleteMongoId = fields || idName !== '_id';
+
     cursor.toArray(function(err, data) {
       if (self.debug) {
         debug('all', model, filter, err, data);
@@ -1138,11 +1144,11 @@ MongoDB.prototype.all = function all(model, filter, options, callback) {
         return callback(err);
       }
       var objs = data.map(function(o) {
-        if (idIncluded(fields, self.idName(model))) {
+        if (shouldSetIdValue) {
           self.setIdValue(model, o, o._id);
         }
         // Don't pass back _id if the fields is set
-        if (fields || idName !== '_id') {
+        if (deleteMongoId) {
           delete o._id;
         }
 

test/mongodb.test.js

@@ -1597,12 +1597,12 @@ describe('mongodb connector', function() {
   it('all return should honor filter.fields', function(done) {
     var post = new Post({ title: 'b', content: 'BBB' });
     post.save(function(err, post) {
-      Post.all({ fields: ['title'], where: { title: 'b' }}, function(err, posts) {
+      db.connector.all('Post', { fields: ['title'], where: { title: 'b' }}, {}, function(err, posts) {
         should.not.exist(err);
         posts.should.have.lengthOf(1);
         post = posts[0];
         post.should.have.property('title', 'b');
-        post.should.have.property('content', undefined);
+        should.not.exist(post.content);
         should.not.exist(post._id);
         should.not.exist(post.id);