Fixed #24603 -- Allowed Context.update() to be used as a context manager.

django/template/context.py

@@ -171,8 +171,7 @@ class Context(BaseContext):
         "Pushes other_dict to the stack of dictionaries in the Context"
         if not hasattr(other_dict, '__getitem__'):
             raise TypeError('other_dict must be a mapping (dictionary-like) object.')
-        self.dicts.append(other_dict)
-        return other_dict
+        return ContextDict(self, other_dict)
 
 
 class RenderContext(BaseContext):

docs/ref/templates/api.txt

@@ -497,6 +497,21 @@ the stack instead of an empty one.
     >>> c['foo']
     'first level'
 
+Like ``push()``, you can use ``update()`` as a context manager to ensure a
+matching ``pop()`` is called.
+
+    >>> c = Context()
+    >>> c['foo'] = 'first level'
+    >>> with c.update({'foo': 'second level'}):
+    ...     c['foo']
+    'second level'
+    >>> c['foo']
+    'first level'
+
+.. versionadded:: 1.9
+
+    The ability to use ``update()`` as a context manager was added.
+
 Using a ``Context`` as a stack comes in handy in :ref:`some custom template
 tags <howto-writing-custom-template-tags>`.
 

docs/releases/1.9.txt

@@ -211,6 +211,9 @@ Templates
 * The :ttag:`firstof` template tag supports storing the output in a variable
   using 'as'.
 
+* :meth:`Context.update() <django.template.Context.update>` can now be used as
+  a context manager.
+
 Requests and Responses
 ^^^^^^^^^^^^^^^^^^^^^^
 

tests/template_tests/test_context.py

@@ -21,6 +21,8 @@ class ContextTests(SimpleTestCase):
         self.assertEqual(c["a"], 1)
         self.assertEqual(c.get("foo", 42), 42)
 
+    def test_push_context_manager(self):
+        c = Context({"a": 1})
         with c.push():
             c['a'] = 2
             self.assertEqual(c['a'], 2)
@@ -30,6 +32,17 @@ class ContextTests(SimpleTestCase):
             self.assertEqual(c['a'], 3)
         self.assertEqual(c['a'], 1)
 
+    def test_update_context_manager(self):
+        c = Context({"a": 1})
+        with c.update({}):
+            c['a'] = 2
+            self.assertEqual(c['a'], 2)
+        self.assertEqual(c['a'], 1)
+
+        with c.update({'a': 3}):
+            self.assertEqual(c['a'], 3)
+        self.assertEqual(c['a'], 1)
+
     def test_setdefault(self):
         c = Context()