Made it possible to have non-expiring keys

Thanks to Kami for the report and Jezdez for being awesome.

redis_cache/cache.py

@@ -85,9 +85,17 @@ class CacheClass(BaseCache):
         """
         Set content expiration, if necessary
         """
-        if timeout is None:
-            timeout = self.default_timeout
-        self._cache.expire(key, timeout)
+        if timeout == 0:
+            # force the key to be non-volatile
+            result = self._cache.get(key)
+            self._cache.set(key, result)
+        else:
+            timeout = timeout or self.default_timeout
+            # If the expiration command returns false, we need to reset the key
+            # with the new expiration
+            if not self._cache.expire(key, timeout):
+                value = self.get(key)
+                self.set(key, value, timeout)
 
     def delete(self, key):
         """

tests/testapp/tests.py

@@ -3,6 +3,11 @@
 import time
 import unittest
 
+try:
+    import cPickle as pickle
+except ImportError:
+    import pickle
+
 from django.core.cache import get_cache
 from models import Poll, expensive_calculation
 
@@ -160,6 +165,40 @@ class RedisCacheTests(unittest.TestCase):
         self.assertEqual(self.cache.get("expire2"), "newvalue")
         self.assertEqual(self.cache.has_key("expire3"), False)
 
+    def test_set_expiration_timeout_None(self):
+        key, value = 'key', 'value'
+        self.cache.set(key, value);
+        self.assertTrue(self.cache._cache.ttl(key) > 0)
+
+    def test_set_expiration_timeout_0(self):
+        key, value = 'key', 'value'
+        self.cache.set(key, value);
+        self.assertTrue(self.cache._cache.ttl(key) > 0)
+        self.cache.expire(key, 0)
+        self.assertEqual(self.cache.get(key), value)
+        self.assertTrue(self.cache._cache.ttl(key) < 0)
+
+    def test_set_expiration_first_expire_call(self):
+        key, value = self.cache.prepare_key('key'), 'value'
+        # bypass public set api so we don't set the expiration
+        self.cache._cache.set(key, pickle.dumps(value))
+        self.cache.expire(key, 1)
+        time.sleep(2)
+        self.assertEqual(self.cache.get('key'), None)
+
+    def test_set_expiration_mulitple_expire_calls(self):
+        key, value = 'key', 'value'
+        self.cache.set(key, value, 1)
+        time.sleep(2)
+        self.assertEqual(self.cache.get('key'), None)
+        self.cache.set(key, value, 100)
+        self.assertEqual(self.cache.get('key'), value)
+        time.sleep(2)
+        self.assertEqual(self.cache.get('key'), value)
+        self.cache.expire(key, 1)
+        time.sleep(2)
+        self.assertEqual(self.cache.get('key'), None)
+
     def test_unicode(self):
         # Unicode values can be cached
         stuff = {