Add more tests

synapse/handlers/sliding_sync.py

@@ -769,26 +769,29 @@ async def get_room_sync_data(
                 and rooms_for_user_membership_at_to_token.membership == Membership.JOIN
             ):
                 newly_joined = (
-                    rooms_for_user_membership_at_to_token.event_pos.stream
-                    > from_token.room_key.get_stream_pos_for_instance(
-                        rooms_for_user_membership_at_to_token.event_pos.instance_name
+                    rooms_for_user_membership_at_to_token.event_pos.persisted_after(
+                        from_token.room_key
                     )
                 )
 
+            # We should return historical messages (before token range) in the
+            # following cases because we want clients to be able to show a basic
+            # screen of information:
+            #  - Initial sync (because no `from_token` to limit us anyway)
+            #  - When users `newly_joined`
+            #  - TODO: For an incremental sync where we haven't sent it down this
+            #    connection before
+            should_limit_timeline_to_token_range = (
+                from_token is not None and not newly_joined
+            )
+
             timeline_events, new_room_key = await self.store.paginate_room_events(
                 room_id=room_id,
                 # We're going to paginate backwards from the `to_token`
                 from_key=to_token.room_key,
-                # We should return historical messages (before token range) in the
-                # following cases because we want clients to be able to show a basic
-                # screen of information:
-                #  - Initial sync (because no `from_token` to limit us anyway)
-                #  - When users `newly_joined`
-                #  - TODO: For an incremental sync where we haven't sent it down this
-                #    connection before
                 to_key=(
                     from_token.room_key
-                    if from_token is not None and not newly_joined
+                    if should_limit_timeline_to_token_range
                     else None
                 ),
                 direction=Direction.BACKWARDS,
@@ -832,7 +835,7 @@ async def get_room_sync_data(
             # old events in the timeline)
             num_live = 0
             if from_token is not None:
-                for timeline_event in timeline_events:
+                for timeline_event in reversed(timeline_events):
                     # This fields should be present for all persisted events
                     assert timeline_event.internal_metadata.stream_ordering is not None
                     assert timeline_event.internal_metadata.instance_name is not None
@@ -843,6 +846,12 @@ async def get_room_sync_data(
                     )
                     if persisted_position.persisted_after(from_token.room_key):
                         num_live += 1
+                    else:
+                        # Since we're iterating over the timeline events in
+                        # reverse-chronological order, we can break once we hit an event
+                        # that's not live. In the future, we could potentially optimize
+                        # this more with a binary search (bisect).
+                        break
 
             prev_batch_token = prev_batch_token.copy_and_replace(
                 StreamKeyType.ROOM, new_room_key

synapse/rest/client/sync.py

@@ -785,7 +785,7 @@ class SlidingSyncRestServlet(RestServlet):
 
     Response JSON::
         {
-            "next_pos": "s58_224_0_13_10_1_1_16_0_1",
+            "pos": "s58_224_0_13_10_1_1_16_0_1",
             "lists": {
                 "foo-list": {
                     "count": 1337,
@@ -824,7 +824,8 @@ class SlidingSyncRestServlet(RestServlet):
                     "joined_count": 41,
                     "invited_count": 1,
                     "notification_count": 1,
-                    "highlight_count": 0
+                    "highlight_count": 0,
+                    "num_live": 2"
                 },
                 // rooms from list
                 "!foo:bar": {
@@ -849,7 +850,8 @@ class SlidingSyncRestServlet(RestServlet):
                     "joined_count": 4,
                     "invited_count": 0,
                     "notification_count": 54,
-                    "highlight_count": 3
+                    "highlight_count": 3,
+                    "num_live": 1,
                 },
                  // ... 99 more items
             },
@@ -927,7 +929,7 @@ async def encode_response(
     ) -> JsonDict:
         response: JsonDict = defaultdict(dict)
 
-        response["next_pos"] = await sliding_sync_result.next_pos.to_string(self.store)
+        response["pos"] = await sliding_sync_result.next_pos.to_string(self.store)
         serialized_lists = self.encode_lists(sliding_sync_result.lists)
         if serialized_lists:
             response["lists"] = serialized_lists

synapse/types/__init__.py

@@ -1078,6 +1078,9 @@ class PersistedPosition:
     stream: int
 
     def persisted_after(self, token: AbstractMultiWriterStreamToken) -> bool:
+        """
+        Checks whether this position happened after the token
+        """
         return token.get_stream_pos_for_instance(self.instance_name) < self.stream