[1.11.x] Fixed #28601 -- Prevented cache.get_or_set() from caching None if default is a callable that returns None.

Backport of 4d60261b2a77460b4c127c3d832518b95e11a0ac from master

1 files changed, 7 insertions, 5 deletions

diff --git a/django/core/cache/backends/base.py b/django/core/cache/backends/base.py
index 9cbfe0be1d..1235f7e098 100644
--- a/django/core/cache/backends/base.py
+++ b/django/core/cache/backends/base.py
@@ -157,13 +157,15 @@ class BaseCache(object):
         Return the value of the key stored or retrieved.
         """
         val = self.get(key, version=version)
-        if val is None and default is not None:
+        if val is None:
             if callable(default):
                 default = default()
-            self.add(key, default, timeout=timeout, version=version)
-            # Fetch the value again to avoid a race condition if another caller
-            # added a value between the first get() and the add() above.
-            return self.get(key, default, version=version)
+            if default is not None:
+                self.add(key, default, timeout=timeout, version=version)
+                # Fetch the value again to avoid a race condition if another
+                # caller added a value between the first get() and the add()
+                # above.
+                return self.get(key, default, version=version)
         return val
 
     def has_key(self, key, version=None):