Merge pull request #177 from sbook/feature/update_lists

Added the ability to update individual items in ListFields.

Example: 
  
   Message.objects(pk=12).update(set__comments__5__body="Testing 123")

mongoengine/queryset.py

@@ -522,6 +522,15 @@ class QuerySet(object):
         fields = []
         field = None
         for field_name in parts:
+            # Handle ListField indexing:
+            if field_name.isdigit():
+                try:
+                    field = field.field
+                except AttributeError, err:
+                    raise InvalidQueryError(
+                        "Can't use index on unsubscriptable field (%s)" % err)
+                fields.append(field_name)
+                continue
             if field is None:
                 # Look up first field from the document
                 if field_name == 'pk':
@@ -1070,10 +1079,17 @@ class QuerySet(object):
             if _doc_cls:
                 # Switch field names to proper names [set in Field(name='foo')]
                 fields = QuerySet._lookup_field(_doc_cls, parts)
-                parts = [field.db_field for field in fields]
+                parts = []
+
+                for field in fields:
+                    if isinstance(field, str):
+                        parts.append(field)
+                    else:
+                        parts.append(field.db_field)
 
                 # Convert value to proper value
                 field = fields[-1]
+
                 if op in (None, 'set', 'push', 'pull', 'addToSet'):
                     value = field.prepare_query_value(op, value)
                 elif op in ('pushAll', 'pullAll'):

tests/queryset.py

@@ -212,6 +212,55 @@ class QuerySetTest(unittest.TestCase):
 
         Blog.drop_collection()
 
+    def test_update_array_position(self):
+        """Ensure that updating by array position works.
+
+        Check update() and update_one() can take syntax like:
+            set__posts__1__comments__1__name="testc"
+        Check that it only works for ListFields.
+        """
+        class Comment(EmbeddedDocument):
+            name = StringField()
+
+        class Post(EmbeddedDocument):
+            comments = ListField(EmbeddedDocumentField(Comment))
+
+        class Blog(Document):
+            tags = ListField(StringField())
+            posts = ListField(EmbeddedDocumentField(Post))
+
+        Blog.drop_collection()
+
+        comment1 = Comment(name='testa')
+        comment2 = Comment(name='testb')
+        post1 = Post(comments=[comment1, comment2])
+        post2 = Post(comments=[comment2, comment2])
+        blog1 = Blog.objects.create(posts=[post1, post2])
+        blog2 = Blog.objects.create(posts=[post2, post1])
+
+        # Update all of the first comments of second posts of all blogs
+        blog = Blog.objects().update(set__posts__1__comments__0__name="testc")
+        testc_blogs = Blog.objects(posts__1__comments__0__name="testc")
+        self.assertEqual(len(testc_blogs), 2)
+
+        Blog.drop_collection()
+
+        blog1 = Blog.objects.create(posts=[post1, post2])
+        blog2 = Blog.objects.create(posts=[post2, post1])
+
+        # Update only the first blog returned by the query
+        blog = Blog.objects().update_one(
+            set__posts__1__comments__1__name="testc")
+        testc_blogs = Blog.objects(posts__1__comments__1__name="testc")
+        self.assertEqual(len(testc_blogs), 1)
+
+        # Check that using this indexing syntax on a non-list fails
+        def non_list_indexing():
+            Blog.objects().update(set__posts__1__comments__0__name__1="asdf")
+        self.assertRaises(InvalidQueryError, non_list_indexing)
+
+        Blog.drop_collection()
+
     def test_get_or_create(self):
         """Ensure that ``get_or_create`` returns one result or creates a new
         document.