Prevent expired events from being filtered out when retention is disabled (#12611)

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

tests/rest/client/test_retention.py

@@ -11,6 +11,7 @@
 # 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.
+from typing import Any, Dict
 from unittest.mock import Mock
 
 from twisted.test.proto_helpers import MemoryReactor
@@ -252,16 +253,24 @@ class RetentionNoDefaultPolicyTestCase(unittest.HomeserverTestCase):
         room.register_servlets,
     ]
 
-    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
-        config = self.default_config()
-        config["retention"] = {
+    def default_config(self) -> Dict[str, Any]:
+        config = super().default_config()
+
+        retention_config = {
             "enabled": True,
         }
 
+        # Update this config with what's in the default config so that
+        # override_config works as expected.
+        retention_config.update(config.get("retention", {}))
+        config["retention"] = retention_config
+
+        return config
+
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
         mock_federation_client = Mock(spec=["backfill"])
 
         self.hs = self.setup_test_homeserver(
-            config=config,
             federation_client=mock_federation_client,
         )
         return self.hs
@@ -295,6 +304,24 @@ class RetentionNoDefaultPolicyTestCase(unittest.HomeserverTestCase):
 
         self._test_retention(room_id, expected_code_for_first_event=404)
 
+    @unittest.override_config({"retention": {"enabled": False}})
+    def test_visibility_when_disabled(self) -> None:
+        """Retention policies should be ignored when the retention feature is disabled."""
+        room_id = self.helper.create_room_as(self.user_id, tok=self.token)
+
+        self.helper.send_state(
+            room_id=room_id,
+            event_type=EventTypes.Retention,
+            body={"max_lifetime": one_day_ms},
+            tok=self.token,
+        )
+
+        resp = self.helper.send(room_id=room_id, body="test", tok=self.token)
+
+        self.reactor.advance(one_day_ms * 2 / 1000)
+
+        self.get_event(room_id, resp["event_id"])
+
     def _test_retention(
         self, room_id: str, expected_code_for_first_event: int = 200
     ) -> None: