Fixed sum and average queryset function

* Fixed sum and average map reduce functions for sum and average so that
        it works with mongo dot notation.

* Added unittest cases / updated them for the new changes

mongoengine/queryset/queryset.py

@@ -1068,7 +1068,22 @@ class QuerySet(object):
         """
         map_func = Code("""
             function() {
-                emit(1, eval("this." + field) || 0);
+                function deepFind(obj, path) {
+                  var paths = path.split('.')
+                    , current = obj
+                    , i;
+
+                  for (i = 0; i < paths.length; ++i) {
+                    if (current[paths[i]] == undefined) {
+                      return undefined;
+                    } else {
+                      current = current[paths[i]];
+                    }
+                  }
+                  return current;
+                }
+
+                emit(1, deepFind(this, field) || 0);
             }
         """, scope={'field': field})
 
@@ -1098,8 +1113,24 @@ class QuerySet(object):
         """
         map_func = Code("""
             function() {
-                if (this.hasOwnProperty(field))
-                    emit(1, {t: eval("this." + field) || 0, c: 1});
+                function deepFind(obj, path) {
+                  var paths = path.split('.')
+                    , current = obj
+                    , i;
+
+                  for (i = 0; i < paths.length; ++i) {
+                    if (current[paths[i]] == undefined) {
+                      return undefined;
+                    } else {
+                      current = current[paths[i]];
+                    }
+                  }
+                  return current;
+                }
+
+                val = deepFind(this, field)
+                if (val !== undefined)
+                    emit(1, {t: val || 0, c: 1});
             }
         """, scope={'field': field})
 

tests/queryset/queryset.py

@@ -30,12 +30,17 @@ class QuerySetTest(unittest.TestCase):
     def setUp(self):
         connect(db='mongoenginetest')
 
+        class PersonMeta(EmbeddedDocument):
+            weight = IntField()
+
         class Person(Document):
             name = StringField()
             age = IntField()
+            person_meta = EmbeddedDocumentField(PersonMeta)
             meta = {'allow_inheritance': True}
 
         Person.drop_collection()
+        self.PersonMeta = PersonMeta
         self.Person = Person
 
     def test_initialisation(self):
@@ -2208,6 +2213,19 @@ class QuerySetTest(unittest.TestCase):
         self.Person(name='ageless person').save()
         self.assertEqual(int(self.Person.objects.average('age')), avg)
 
+        # dot notation
+        self.Person(name='person meta', person_meta=self.PersonMeta(weight=0)).save()
+        self.assertAlmostEqual(int(self.Person.objects.average('person_meta.weight')), 0)
+
+        for i, weight in enumerate(ages):
+            self.Person(name='test meta%i', person_meta=self.PersonMeta(weight=weight)).save()
+
+        self.assertAlmostEqual(int(self.Person.objects.average('person_meta.weight')), avg)
+
+        self.Person(name='test meta none').save()
+        self.assertEqual(int(self.Person.objects.average('person_meta.weight')), avg)
+
+
     def test_sum(self):
         """Ensure that field can be summed over correctly.
         """
@@ -2220,6 +2238,14 @@ class QuerySetTest(unittest.TestCase):
         self.Person(name='ageless person').save()
         self.assertEqual(int(self.Person.objects.sum('age')), sum(ages))
 
+        for i, age in enumerate(ages):
+            self.Person(name='test meta%s' % i, person_meta=self.PersonMeta(weight=age)).save()
+
+        self.assertEqual(int(self.Person.objects.sum('person_meta.weight')), sum(ages))
+
+        self.Person(name='weightless person').save()
+        self.assertEqual(int(self.Person.objects.sum('age')), sum(ages))
+
     def test_distinct(self):
         """Ensure that the QuerySet.distinct method works.
         """