position support singular value #1565

mongoengine/queryset/transform.py

@@ -304,10 +304,6 @@ def update(_doc_cls=None, **update):
             value = {match: value}
 
         key = '.'.join(parts)
-        position = None
-        if parts[-1].isdigit() and isinstance(value, (list, tuple, set)):
-            key = parts[0]
-            position = int(parts[-1])
 
         if not op:
             raise InvalidQueryError('Updates must supply an operation '
@@ -339,13 +335,20 @@ def update(_doc_cls=None, **update):
                 value = {key: value}
         elif op == 'addToSet' and isinstance(value, list):
             value = {key: {'$each': value}}
-        elif op == 'push' and isinstance(value, list):
+        elif op == 'push':
-            if position is not None:
+            if parts[-1].isdigit() and op == 'push':
+                key = parts[0]
+                position = int(parts[-1])
+                # position modifier must appear with each.
+                if not isinstance(value, (set, tuple, list)):
+                    value = [value]
                 value = {key: {'$each': value, '$position': position}}
-            else:
+            elif isinstance(value, list):
                 value = {key: {'$each': value}}
             else:
                 value = {key: value}
+        else:
+            value = {key: value}
         key = '$' + op
         if key not in mongo_update:
             mongo_update[key] = value

tests/queryset/queryset.py

@@ -1925,6 +1925,11 @@ class QuerySetTest(unittest.TestCase):
         post.reload()
         self.assertEqual(post.tags, ['mongodb', 'python', 'java'])
 
+        #test push with singular value
+        BlogPost.objects.filter(id=post.id).update(push__tags__0='scala')
+        post.reload()
+        self.assertEqual(post.tags, ['scala', 'mongodb', 'python', 'java'])
+
     def test_update_push_and_pull_add_to_set(self):
         """Ensure that the 'pull' update operation works correctly.
         """