Support spaces with > 50 rooms in the /hierarchy endpoint

changelog.d/11695.bugfix

@@ -0,0 +1 @@
+Fix a bug where the only the first 50 rooms from a space were return from the `/hierarchy` API. This has existed since the introduction of the API in Synapse v1.41.0.

synapse/handlers/room_summary.py

@@ -153,6 +153,9 @@ async def get_space_summary(
         rooms_result: List[JsonDict] = []
         events_result: List[JsonDict] = []
 
+        if max_rooms_per_space is None or max_rooms_per_space > MAX_ROOMS_PER_SPACE:
+            max_rooms_per_space = MAX_ROOMS_PER_SPACE
+
         while room_queue and len(rooms_result) < MAX_ROOMS:
             queue_entry = room_queue.popleft()
             room_id = queue_entry.room_id
@@ -167,7 +170,7 @@ async def get_space_summary(
             # The client-specified max_rooms_per_space limit doesn't apply to the
             # room_id specified in the request, so we ignore it if this is the
             # first room we are processing.
-            max_children = max_rooms_per_space if processed_rooms else None
+            max_children = max_rooms_per_space if processed_rooms else MAX_ROOMS
 
             if is_in_room:
                 room_entry = await self._summarize_local_room(
@@ -395,7 +398,7 @@ async def _get_room_hierarchy(
                     None,
                     room_id,
                     suggested_only,
-                    # TODO Handle max children.
+                    # Do not limit the maximum children.
                     max_children=None,
                 )
 
@@ -525,6 +528,10 @@ async def federation_space_summary(
         rooms_result: List[JsonDict] = []
         events_result: List[JsonDict] = []
 
+        # Set a limit on the number of rooms to return.
+        if max_rooms_per_space is None or max_rooms_per_space > MAX_ROOMS_PER_SPACE:
+            max_rooms_per_space = MAX_ROOMS_PER_SPACE
+
         while room_queue and len(rooms_result) < MAX_ROOMS:
             room_id = room_queue.popleft()
             if room_id in processed_rooms:
@@ -583,7 +590,9 @@ async def get_federation_hierarchy(
 
         # Iterate through each child and potentially add it, but not its children,
         # to the response.
-        for child_room in root_room_entry.children_state_events:
+        for child_room in itertools.islice(
+            root_room_entry.children_state_events, MAX_ROOMS_PER_SPACE
+        ):
             room_id = child_room.get("state_key")
             assert isinstance(room_id, str)
             # If the room is unknown, skip it.
@@ -633,8 +642,8 @@ async def _summarize_local_room(
             suggested_only: True if only suggested children should be returned.
                 Otherwise, all children are returned.
             max_children:
-                The maximum number of children rooms to include. This is capped
-                to a server-set limit.
+                The maximum number of children rooms to include. A value of None
+                means no limit.
 
         Returns:
             A room entry if the room should be returned. None, otherwise.
@@ -656,8 +665,13 @@ async def _summarize_local_room(
             # we only care about suggested children
             child_events = filter(_is_suggested_child_event, child_events)
 
-        if max_children is None or max_children > MAX_ROOMS_PER_SPACE:
-            max_children = MAX_ROOMS_PER_SPACE
+        # TODO max_children is legacy code for the /spaces endpoint.
+        if max_children is not None:
+            child_iter: Iterable[EventBase] = itertools.islice(
+                child_events, max_children
+            )
+        else:
+            child_iter = child_events
 
         stripped_events: List[JsonDict] = [
             {
@@ -668,7 +682,7 @@ async def _summarize_local_room(
                 "sender": e.sender,
                 "origin_server_ts": e.origin_server_ts,
             }
-            for e in itertools.islice(child_events, max_children)
+            for e in child_iter
         ]
         return _RoomEntry(room_id, room_entry, stripped_events)
 

tests/handlers/test_room_summary.py

@@ -253,6 +253,38 @@ def test_simple_space(self):
         )
         self._assert_hierarchy(result, expected)
 
+    def test_large_space(self):
+        """Test a space with a large number of rooms."""
+        rooms = [self.room]
+        # Make at least 51 rooms that are part of the space.
+        for _ in range(55):
+            room = self.helper.create_room_as(self.user, tok=self.token)
+            self._add_child(self.space, room, self.token)
+            rooms.append(room)
+
+        result = self.get_success(self.handler.get_space_summary(self.user, self.space))
+        # The spaces result should have the space and the first 50 rooms in it,
+        # along with the links from space -> room for those 50 rooms.
+        expected = [(self.space, rooms[:50])] + [(room, []) for room in rooms[:49]]
+        self._assert_rooms(result, expected)
+
+        # The result should have the space and the rooms in it, along with the links
+        # from space -> room.
+        expected = [(self.space, rooms)] + [(room, []) for room in rooms]
+
+        # Make two requests to fully paginate the results.
+        result = self.get_success(
+            self.handler.get_room_hierarchy(create_requester(self.user), self.space)
+        )
+        result2 = self.get_success(
+            self.handler.get_room_hierarchy(
+                create_requester(self.user), self.space, from_token=result["next_batch"]
+            )
+        )
+        # Combine the results.
+        result["rooms"] += result2["rooms"]
+        self._assert_hierarchy(result, expected)
+
     def test_visibility(self):
         """A user not in a space cannot inspect it."""
         user2 = self.register_user("user2", "pass")