Make sure batch create calls back with correct data

See https://github.com/strongloop/loopback/issues/1031

lib/dao.js

@@ -160,39 +160,38 @@ DataAccessObject.create = function (data, callback) {
   }
 
   if (Array.isArray(data)) {
-    var instances = [];
+    // Undefined item will be skipped by async.map() which internally uses
-    var errors = Array(data.length);
+    // Array.prototype.map(). The following loop makes sure all items are
-    var gotError = false;
+    // iterated
-    var wait = data.length;
+    for (var i = 0, n = data.length; i < n; i++) {
-    if (wait === 0) {
+      if (data[i] === undefined) {
-      callback(null, []);
+        data[i] = {};
-    }
-
-    for (var i = 0; i < data.length; i += 1) {
-      (function (d, i) {
-        Model = self.lookupModel(d); // data-specific
-        instances.push(Model.create(d, function (err, inst) {
-          if (err) {
-            errors[i] = err;
-            gotError = true;
-          }
-          modelCreated();
-        }));
-      })(data[i], i);
-    }
-
-    return instances;
-
-    function modelCreated() {
-      if (--wait === 0) {
-        callback(gotError ? errors : null, instances);
-        if(!gotError) {
-          instances.forEach(function(inst) {
-            inst.constructor.emit('changed');
-          });
-        }
       }
     }
+    async.map(data, function(item, done) {
+      self.create(item, function(err, result) {
+        // Collect all errors and results
+        done(null, {err: err, result: result || item});
+      });
+    }, function(err, results) {
+      if (err) {
+        return callback && callback(err, results);
+      }
+      // Convert the results into two arrays
+      var errors = null;
+      var data = [];
+      for (var i = 0, n = results.length; i < n; i++) {
+        if (results[i].err) {
+          if (!errors) {
+            errors = [];
+          }
+          errors[i] = results[i].err;
+        }
+        data[i] = results[i].result;
+      }
+      callback && callback(errors, data);
+    });
+    return data;
   }
 
   var enforced = {};

test/manipulation.test.js

@@ -153,6 +153,29 @@ describe('manipulation', function () {
         }).should.be.instanceOf(Array);
       }).should.have.lengthOf(3);
     });
+
+    it('should create batch of objects with beforeCreate', function(done) {
+      Person.beforeCreate = function(next, data) {
+        if (data && data.name === 'A') {
+          return next(null, {id: 'a', name: 'A'});
+        } else {
+          return next();
+        }
+      };
+      var batch = [
+        {name: 'A'},
+        {name: 'B'},
+        undefined
+      ];
+      Person.create(batch, function(e, ps) {
+        should.not.exist(e);
+        should.exist(ps);
+        ps.should.be.instanceOf(Array);
+        ps.should.have.lengthOf(batch.length);
+        ps[0].should.be.eql({id: 'a', name: 'A'});
+        done();
+      });
+    });
   });
 
   describe('save', function () {