Fixed inner queryset looping (#204)

AUTHORS

@@ -143,3 +143,4 @@ that much better:
  * Martin Alderete (https://github.com/malderete)
  * Nick Joyce
  * Jared Forsyth
+ * Kenneth Falck

docs/changelog.rst

@@ -47,6 +47,7 @@ Changes in 0.8.X
 - Added the "get_decoded" method to the MongoSession class (#216)
 - Fixed invalid choices error bubbling (#214)
 - Updated Save so it calls $set and $unset in a single operation (#211)
+- Fixed inner queryset looping (#204)
 
 Changes in 0.7.9
 ================

mongoengine/queryset/queryset.py

@@ -112,8 +112,11 @@ class QuerySet(object):
 
     def __iter__(self):
         """Support iterator protocol"""
-        self.rewind()
-        return self
+        queryset = self
+        if queryset._iter:
+            queryset = self.clone()
+        queryset.rewind()
+        return queryset
 
     def __len__(self):
         return self.count()
@@ -159,7 +162,6 @@ class QuerySet(object):
 
         .. versionchanged:: 0.6.13 Now doesnt modify the cursor
         """
-
         if self._iter:
             return '.. queryset mid-iteration ..'
 
@@ -537,7 +539,7 @@ class QuerySet(object):
             c._cursor_obj = self._cursor_obj.clone()
 
         if self._slice:
-            c._cursor_obj[self._slice]
+            c._cursor[self._slice]
 
         return c
 

tests/queryset/queryset.py

@@ -3125,5 +3125,46 @@ class QuerySetTest(unittest.TestCase):
                                     Organization))
         self.assertTrue(isinstance(qs.first().organization, Organization))
 
+    def test_nested_queryset_iterator(self):
+        # Try iterating the same queryset twice, nested.
+        names = ['Alice', 'Bob', 'Chuck', 'David', 'Eric', 'Francis', 'George']
+
+        class User(Document):
+            name = StringField()
+
+            def __unicode__(self):
+                return self.name
+
+        User.drop_collection()
+
+        for name in names:
+            User(name=name).save()
+
+        users = User.objects.all().order_by('name')
+
+        outer_count = 0
+        inner_count = 0
+        inner_total_count = 0
+
+        self.assertEqual(len(users), 7)
+
+        for i, outer_user in enumerate(users):
+            self.assertEqual(outer_user.name, names[i])
+            outer_count += 1
+            inner_count = 0
+
+            # Calling len might disrupt the inner loop if there are bugs
+            self.assertEqual(len(users), 7)
+
+            for j, inner_user in enumerate(users):
+                self.assertEqual(inner_user.name, names[j])
+                inner_count += 1
+                inner_total_count += 1
+
+            self.assertEqual(inner_count, 7) # inner loop should always be executed seven times
+
+        self.assertEqual(outer_count, 7) # outer loop should be executed seven times total
+        self.assertEqual(inner_total_count, 7 * 7) # inner loop should be executed fourtynine times total
+
 if __name__ == '__main__':
     unittest.main()

tests/test_django.py

@@ -136,7 +136,25 @@ class QuerySetTest(unittest.TestCase):
             start = end - 1
             self.assertEqual(t.render(Context(d)), u'%d:%d:' % (start, end))
 
+    def test_nested_queryset_template_iterator(self):
+        # Try iterating the same queryset twice, nested, in a Django template.
+        names = ['A', 'B', 'C', 'D']
 
+        class User(Document):
+            name = StringField()
+
+            def __unicode__(self):
+                return self.name
+
+        User.drop_collection()
+
+        for name in names:
+            User(name=name).save()
+
+        users = User.objects.all().order_by('name')
+        template = Template("{% for user in users %}{{ user.name }}{% ifequal forloop.counter 2 %} {% for inner_user in users %}{{ inner_user.name }}{% endfor %} {% endifequal %}{% endfor %}")
+        rendered = template.render(Context({'users': users}))
+        self.assertEqual(rendered, 'AB ABCD CD')
 
 class MongoDBSessionTest(SessionTestsMixin, unittest.TestCase):
     backend = SessionStore