None result obtained from cache

peterbe · Oct 12, 2018 · fda8f8b · fda8f8b
1 parent 4674dfd
commit fda8f8b
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Showing 2 changed files with 24 additions and 3 deletions.
diff --git a/src/cache_memoize/__init__.py b/src/cache_memoize/__init__.py
@@ -1,10 +1,11 @@
+import hashlib
 from functools import wraps
 
-import hashlib
 from django.core.cache import caches, DEFAULT_CACHE_ALIAS
-
 from django.utils.encoding import force_text, force_bytes
 
+NONE_PLACEHOLDER = '___NONE_PLACEHOLDER___'
+
 
 def cache_memoize(
     timeout,
@@ -81,7 +82,7 @@ def callmeonce(arg1):
         def noop(*args):
             return args
         args_rewrite = noop
-    
+
     cache = caches[cache_alias]
 
     def decorator(func):
@@ -112,10 +113,14 @@ def inner(*args, **kwargs):
                     cache.set(cache_key, True, timeout)
                 elif result is not None:
                     cache.set(cache_key, result, timeout)
+                else:
+                    cache.set(cache_key, NONE_PLACEHOLDER, timeout)
                 if miss_callable:
                     miss_callable(*args, **kwargs)
             elif hit_callable:
                 hit_callable(*args, **kwargs)
+            if result == NONE_PLACEHOLDER:
+                result = None
             return result
 
         def invalidate(*args, **kwargs):

diff --git a/tests/test_cache_memoize.py b/tests/test_cache_memoize.py
@@ -202,3 +202,19 @@ def runmeonce(a):
     assert len(calls_made) == 2
     runmeonce_locmem(10)
     assert len(calls_made) == 2
+
+
+def test_cache_memoize_empty_placeholder():
+    calls_made = []
+
+    @cache_memoize(10)
+    def runmeonce(a):
+        calls_made.append(a)
+
+    result = runmeonce(20)
+    assert len(calls_made) == 1
+    assert result is None
+    result = runmeonce(20)
+    runmeonce(20)
+    assert len(calls_made) == 1
+    assert result is None