[1.9.x] Fixed #25840 -- Fixed BaseCache.get_or_set() on the DummyCache backend.

This also fixes a possible data eviction race condition between
setting and getting a key. Another thread could remove the key
before get_and_set() accesses it again. In this case, now the
default value will be returned instead of None.

Backport of 8e838d9c869083597dc9e161ae2fe37acaa90de9 from master

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/cache/tests.py b/tests/cache/tests.py
index dca08ee081..7fd9808ca6 100644
--- a/tests/cache/tests.py
+++ b/tests/cache/tests.py
@@ -197,6 +197,15 @@ class DummyCacheTests(SimpleTestCase):
         self.assertRaises(ValueError, cache.decr_version, 'answer')
         self.assertRaises(ValueError, cache.decr_version, 'does_not_exist')
 
+    def test_get_or_set(self):
+        self.assertEqual(cache.get_or_set('mykey', 'default'), 'default')
+
+    def test_get_or_set_callable(self):
+        def my_callable():
+            return 'default'
+
+        self.assertEqual(cache.get_or_set('mykey', my_callable), 'default')
+
 
 def custom_key_func(key, key_prefix, version):
     "A customized cache key function"