Fixed #22606 -- Locmemcache has_key() failed for infinite cache expiry

Refactored cache expiry logic for Locmemcache to make consistent across
all places where accessed, and correctly handle None as expiry time.

django/core/cache/backends/locmem.py

@@ -29,8 +29,7 @@ class LocMemCache(BaseCache):
         self.validate_key(key)
         pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
         with self._lock.writer():
-            exp = self._expire_info.get(key, 0)
-            if exp is not None and exp <= time.time():
+            if self._has_expired(key):
                 self._set(key, pickled, timeout)
                 return True
             return False
@@ -40,8 +39,7 @@ class LocMemCache(BaseCache):
         self.validate_key(key)
         pickled = None
         with self._lock.reader():
-            exp = self._expire_info.get(key, 0)
-            if exp is None or exp > time.time():
+            if not self._has_expired(key):
                 pickled = self._cache[key]
         if pickled is not None:
             try:
@@ -85,10 +83,7 @@ class LocMemCache(BaseCache):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         with self._lock.reader():
-            exp = self._expire_info.get(key)
-            if exp is None:
-                return False
-            elif exp > time.time():
+            if not self._has_expired(key):
                 return True
 
         with self._lock.writer():
@@ -99,6 +94,12 @@ class LocMemCache(BaseCache):
                 pass
             return False
 
+    def _has_expired(self, key):
+        exp = self._expire_info.get(key, -1)
+        if exp is None or exp > time.time():
+            return False
+        return True
+
     def _cull(self):
         if self._cull_frequency == 0:
             self.clear()

tests/cache/tests.py

@@ -285,6 +285,8 @@ class BaseCacheTests(object):
         cache.set("hello1", "goodbye1")
         self.assertEqual(cache.has_key("hello1"), True)
         self.assertEqual(cache.has_key("goodbye1"), False)
+        cache.set("no_expiry", "here", None)
+        self.assertEqual(cache.has_key("no_expiry"), True)
 
     def test_in(self):
         # The in operator can be used to inspect cache contents