Merge pull request #287 from wpjunior/fixitem_frequencies

Fix item_frequencies

mongoengine/queryset.py

@@ -1526,7 +1526,12 @@ class QuerySet(object):
             function() {
                 path = '{{~%(field)s}}'.split('.');
                 field = this;
-                for (p in path) { field = field[path[p]]; }
+                for (p in path) {
+                    if (field)
+                       field = field[path[p]];
+                    else
+                       break;
+                }
                 if (field && field.constructor == Array) {
                     field.forEach(function(item) {
                         emit(item, 1);
@@ -1572,7 +1577,12 @@ class QuerySet(object):
                     var total = 0.0;
                     db[collection].find(query).forEach(function(doc) {
                         field = doc;
-                        for (p in path) { field = field[path[p]]; }
+                        for (p in path) {
+                            if (field)
+                                field = field[path[p]];
+                            else
+                                break;
+                        }
                         if (field && field.constructor == Array) {
                             total += field.length;
                         } else {
@@ -1588,7 +1598,12 @@ class QuerySet(object):
                 }
                 db[collection].find(query).forEach(function(doc) {
                     field = doc;
-                    for (p in path) { field = field[path[p]]; }
+                    for (p in path) {
+                        if (field)
+                            field = field[path[p]];
+                        else
+                            break;
+                    }
                     if (field && field.constructor == Array) {
                         field.forEach(function(item) {
                             frequencies[item] = inc + (isNaN(frequencies[item]) ? 0: frequencies[item]);

tests/queryset.py

@@ -1840,6 +1840,36 @@ class QuerySetTest(unittest.TestCase):
         freq = Person.objects.item_frequencies('city', normalize=True, map_reduce=True)
         self.assertEquals(freq, {'CRB': 0.5, None: 0.5})
 
+        
+    def test_item_frequencies_with_null_embedded(self):
+        class Data(EmbeddedDocument):
+            name = StringField()
+
+        class Extra(EmbeddedDocument):
+            tag = StringField()
+
+        class Person(Document):
+            data = EmbeddedDocumentField(Data, required=True)
+            extra = EmbeddedDocumentField(Extra)
+
+
+        Person.drop_collection()
+
+        p = Person()
+        p.data = Data(name="Wilson Jr")
+        p.save()
+
+        p = Person()
+        p.data = Data(name="Wesley")
+        p.extra = Extra(tag="friend")
+        p.save()
+
+        ot = Person.objects.item_frequencies('extra.tag', map_reduce=False)
+        self.assertEquals(ot, {None: 1.0, u'friend': 1.0})
+
+        ot = Person.objects.item_frequencies('extra.tag', map_reduce=True)
+        self.assertEquals(ot, {None: 1.0, u'friend': 1.0})
+
     def test_average(self):
         """Ensure that field can be averaged correctly.
         """