Ticket #14315: django-memcached-negative-delta.diff

django/core/cache/backends/memcached.py

@@ -83 +83 @@
 
     def incr(self, key, delta=1, version=None):
         key = self.make_key(key, version=version)
+        # memcached doesn't support a negative delta
+        if delta < 0:
+            return self._cache.decr(key, -delta)
         try:
             val = self._cache.incr(key, delta)
 
@@ -98 +101 @@
 
     def decr(self, key, delta=1, version=None):
         key = self.make_key(key, version=version)
+        if delta < 0:
+            return self._cache.incr(key, -delta)
         try:
             val = self._cache.decr(key, delta)
 

tests/regressiontests/cache/tests.py

@@ -243 +243 @@
         self.assertEqual(self.cache.incr('answer', 10), 52)
         self.assertEqual(self.cache.get('answer'), 52)
         self.assertRaises(ValueError, self.cache.incr, 'does_not_exist')
+        self.assertEqual(self.cache.incr('answer', -10), 42)
 
     def test_decr(self):
         # Cache values can be decremented
@@ -252 +253 @@
         self.assertEqual(self.cache.decr('answer', 10), 32)
         self.assertEqual(self.cache.get('answer'), 32)
         self.assertRaises(ValueError, self.cache.decr, 'does_not_exist')
-
+        self.assertEqual(self.cache.decr('answer', -10), 42)
+        
     def test_data_types(self):
         # Many different data types can be cached
         stuff = {