diff --git a/synapse/util/caches/dictionary_cache.py b/synapse/util/caches/dictionary_cache.py
index 8b426c005b..588d2d49f2 100644
--- a/synapse/util/caches/dictionary_cache.py
+++ b/synapse/util/caches/dictionary_cache.py
@@ -12,10 +12,11 @@
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
-
+import enum
import logging
import threading
from collections import namedtuple
+from typing import Any
from synapse.util.caches.lrucache import LruCache
@@ -38,23 +39,26 @@ class DictionaryEntry(namedtuple("DictionaryEntry", ("full", "known_absent", "va
return len(self.value)
+class _Sentinel(enum.Enum):
+ # defining a sentinel in this way allows mypy to correctly handle the
+ # type of a dictionary lookup.
+ sentinel = object()
+
+
class DictionaryCache:
"""Caches key -> dictionary lookups, supporting caching partial dicts, i.e.
fetching a subset of dictionary keys for a particular key.
"""
def __init__(self, name, max_entries=1000):
- self.cache = LruCache(max_size=max_entries, cache_name=name, size_callback=len)
+ self.cache = LruCache(
+ max_size=max_entries, cache_name=name, size_callback=len
+ ) # type: LruCache[Any, DictionaryEntry]
self.name = name
self.sequence = 0
self.thread = None
- class Sentinel:
- __slots__ = []
-
- self.sentinel = Sentinel()
-
def check_thread(self):
expected_thread = self.thread
if expected_thread is None:
@@ -76,8 +80,8 @@ class DictionaryCache:
Returns:
DictionaryEntry
"""
- entry = self.cache.get(key, self.sentinel)
- if entry is not self.sentinel:
+ entry = self.cache.get(key, _Sentinel.sentinel)
+ if entry is not _Sentinel.sentinel:
if dict_keys is None:
return DictionaryEntry(
entry.full, entry.known_absent, dict(entry.value)
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