Additional test for cachedList

changelog.d/11246.misc

@@ -0,0 +1 @@
+Add an additional test for the `cachedList` method decorator.

tests/util/caches/test_descriptors.py

@@ -17,6 +17,7 @@
 from unittest import mock
 
 from twisted.internet import defer, reactor
+from twisted.internet.defer import Deferred
 
 from synapse.api.errors import SynapseError
 from synapse.logging.context import (
@@ -703,6 +704,48 @@ async def list_fn(self, args1, arg2):
  obj.mock.assert_called_once_with((40,), 2)
  self.assertEqual(r, {10: "fish", 40: "gravy"})
 
+ def test_concurrent_lookups(self):
+ """All concurrent lookups should get the same result"""
+
+ class Cls:
+ def __init__(self):
+ self.mock = mock.Mock()
+
+ @descriptors.cached()
+ def fn(self, arg1):
+ pass
+
+ @descriptors.cachedList("fn", "args1")
+ def list_fn(self, args1) -> "Deferred[dict]":
+ return self.mock(args1)
+
+ obj = Cls()
+ deferred_result = Deferred()
+ obj.mock.return_value = deferred_result
+
+ # start off several concurrent lookups of the same key
+ d1 = obj.list_fn([10])
+ d2 = obj.list_fn([10])
+ d3 = obj.list_fn([10])
+
+ # the mock should have been called exactly once
+ obj.mock.assert_called_once_with((10,))
+ obj.mock.reset_mock()
+
+ # ... and none of the calls should yet be complete
+ self.assertFalse(d1.called)
+ self.assertFalse(d2.called)
+ self.assertFalse(d3.called)
+
+ # complete the lookup. @cachedList functions need to complete with a map
+ # of input->result
+ deferred_result.callback({10: "peas"})
+
+ # ... which should give the right result to all the callers
+ self.assertEqual(self.successResultOf(d1), {10: "peas"})
+ self.assertEqual(self.successResultOf(d2), {10: "peas"})
+ self.assertEqual(self.successResultOf(d3), {10: "peas"})
+
  @defer.inlineCallbacks
  def test_invalidate(self):
  """Make sure that invalidation callbacks are called."""