SyncResultBuilder: remove excluded rooms

synapse/handlers/sync.py

@@ -1387,15 +1387,6 @@ async def generate_sync_result(
                 if await self.store.is_partial_state_room(room_id)
             )
 
-        # Now we have our list of joined room IDs, exclude as configured and freeze
-        joined_room_ids = frozenset(
-            (
-                room_id
-                for room_id in mutable_joined_room_ids
-                if room_id not in mutable_rooms_to_exclude
-            )
-        )
-
         logger.debug(
             "Calculating sync response for %r between %s and %s",
             sync_config.user,
@@ -1408,7 +1399,7 @@ async def generate_sync_result(
             full_state,
             since_token=since_token,
             now_token=now_token,
-            joined_room_ids=joined_room_ids,
+            joined_room_ids=frozenset(mutable_joined_room_ids),
             excluded_room_ids=frozenset(mutable_rooms_to_exclude),
             membership_change_events=membership_change_events,
         )
@@ -2561,7 +2552,8 @@ class SyncResultBuilder:
         full_state: The full_state flag as specified by user
         since_token: The token supplied by user, or None.
         now_token: The token to sync up to.
-        joined_room_ids: List of rooms the user is joined to
+        joined_room_ids: Set of rooms the user is joined to. The excluded_room_ids
+            are automatically discarded from this set.
         excluded_room_ids: Set of room ids we should omit from the /sync response.
 
         # The following mirror the fields in a sync response
@@ -2590,6 +2582,9 @@ class SyncResultBuilder:
     archived: List[ArchivedSyncResult] = attr.Factory(list)
     to_device: List[JsonDict] = attr.Factory(list)
 
+    def __attrs_post_init__(self) -> None:
+        self.joined_room_ids = self.joined_room_ids - self.excluded_room_ids
+
     def calculate_user_changes(self) -> Tuple[AbstractSet[str], AbstractSet[str]]:
         """Work out which other users have joined or left rooms we are joined to.
 

tests/handlers/test_sync.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.
+import unittest as stdlib_unittest
 from typing import Optional
 from unittest.mock import MagicMock, Mock, patch
 
@@ -20,18 +21,34 @@
 from synapse.api.errors import Codes, ResourceLimitError
 from synapse.api.filtering import Filtering
 from synapse.api.room_versions import RoomVersions
-from synapse.handlers.sync import SyncConfig, SyncResult
+from synapse.handlers.sync import SyncConfig, SyncResult, SyncResultBuilder
 from synapse.rest import admin
 from synapse.rest.client import knock, login, room
 from synapse.server import HomeServer
-from synapse.types import UserID, create_requester
+from synapse.types import StreamToken, UserID, create_requester
 from synapse.util import Clock
 
 import tests.unittest
 import tests.utils
 from tests.test_utils import make_awaitable
 
 
+class TestSyncResultBuilder(stdlib_unittest.TestCase):
+    def test_excluded_rooms_set_is_discard_from_joined_rooms_set(self) -> None:
+        builder = SyncResultBuilder(
+            sync_config=generate_sync_config("@alice:wonderland"),
+            full_state=False,
+            since_token=None,
+            now_token=StreamToken.START,
+            joined_room_ids=frozenset(["a", "b", "c"]),
+            excluded_room_ids=frozenset(["c", "d"]),
+            membership_change_events=[],
+        )
+
+        self.assertEqual(builder.joined_room_ids, {"a", "b"})
+        self.assertEqual(builder.excluded_room_ids, {"c", "d"})
+
+
 class SyncTestCase(tests.unittest.HomeserverTestCase):
     """Tests Sync Handler."""