Merge pull request #1479 from nickbruun/ticket_20924

Proxy __len__ and __contains__ for LazyObject

django/utils/functional.py

@@ -270,6 +270,9 @@ class LazyObject(object):
     def __delitem__(self, key):
         del self[key]
 
+    __len__ = new_method_proxy(len)
+    __contains__ = new_method_proxy(operator.contains)
+
 
 # Workaround for http://bugs.python.org/issue12370
 _super = super

tests/utils_tests/test_simplelazyobject.py

@@ -136,6 +136,9 @@ class TestUtilsSimpleLazyObject(TestCase):
         self.assertEqual(lazydict['one'], 1)
         lazydict['one'] = -1
         self.assertEqual(lazydict['one'], -1)
+        self.assertTrue('one' in lazydict)
+        self.assertFalse('two' in lazydict)
+        self.assertEqual(len(lazydict), 1)
         del lazydict['one']
         with self.assertRaises(KeyError):
             lazydict['one']
@@ -183,3 +186,13 @@ class TestUtilsSimpleLazyObject(TestCase):
 
             # This would fail with "TypeError: expected string or Unicode object, NoneType found".
             pickled = cPickle.dumps(x)
+
+    def test_list_set(self):
+        lazy_list = SimpleLazyObject(lambda: [1, 2, 3, 4, 5])
+        lazy_set = SimpleLazyObject(lambda: set([1, 2, 3, 4]))
+        self.assertTrue(1 in lazy_list)
+        self.assertTrue(1 in lazy_set)
+        self.assertFalse(6 in lazy_list)
+        self.assertFalse(6 in lazy_set)
+        self.assertEqual(len(lazy_list), 5)
+        self.assertEqual(len(lazy_set), 4)