Merge pull request #1413 from maykinmedia/disambiguate-missing-cached…

…-value-from-none

Disambiguate missing cache values from None

src/open_inwoner/utils/decorators.py

@@ -120,11 +120,12 @@ def wrapped(*args, **kwargs) -> RT:
 
             cache_key = cache_key_with_attr_placeholders.format(**key_kwargs)
             logger.debug("Resolved cache_key `%s` to `%s`", key, cache_key)
+
             _cache: BaseCache = caches[alias]
-            result = _cache.get(cache_key)
 
-            # The key exists in cache so we return the already cached data
-            if result is not None:
+            CACHE_MISS = object()
+            result = _cache.get(cache_key, default=CACHE_MISS)
+            if result is not CACHE_MISS:
                 logger.debug("Cache hit: '%s'", cache_key)
                 return result
 

src/open_inwoner/utils/tests/test_utils.py

@@ -55,11 +55,11 @@ def with_static_key(self):
 
         self.cache.get.assert_has_calls(
             [
-                mock.call("alpha:charlie:bravo:42"),
-                mock.call("alpha:bar:bravo:baz"),
-                mock.call("alpha:bar:bravo:5"),
-                mock.call("alpha:bar:bravo:baz:charlie:charlie:42"),
-                mock.call("static"),
+                mock.call("alpha:charlie:bravo:42", default=mock.ANY),
+                mock.call("alpha:bar:bravo:baz", default=mock.ANY),
+                mock.call("alpha:bar:bravo:5", default=mock.ANY),
+                mock.call("alpha:bar:bravo:baz:charlie:charlie:42", default=mock.ANY),
+                mock.call("static", default=mock.ANY),
             ]
         )
 
@@ -201,3 +201,19 @@ def foo():
 
         with self.assertRaises(ValueError):
             foo()
+
+    def test_returning_None_is_not_treated_as_a_cache_miss(self):
+        m = mock.Mock()
+
+        @cache("foo")
+        def returns_none():
+            m()
+            return None
+
+        # The second call should return the cached "None" from the first call,
+        # which the cache decorator should interpret as a valid cached value,
+        # not as a cache miss.
+        returns_none()
+        returns_none()
+
+        m.assert_called_once()