Easy refactors of the user directory (#10789)

No functional changes here. This came out as I was working to tackle #5677 

2 files changed, 8 insertions, 4 deletions

diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py

index c58a4b8690..64c18c6f86 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -196,6 +196,11 @@ class RoomMemberWorkerStore(EventsWorkerStore):
     ) -> Dict[str, ProfileInfo]:
         """Get a mapping from user ID to profile information for all users in a given room.
 
+        The profile information comes directly from this room's `m.room.member`
+        events, and so may be specific to this room rather than part of a user's
+        global profile. To avoid privacy leaks, the profile data should only be
+        revealed to users who are already in this room.
+
         Args:
             room_id: The ID of the room to retrieve the users of.
 
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py

index 65dde67ae9..16d9824ec1 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -196,7 +196,6 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
                 )
 
                 users_with_profile = await self.get_users_in_room_with_profiles(room_id)
-                user_ids = set(users_with_profile)
 
                 # Update each user in the user directory.
                 for user_id, profile in users_with_profile.items():
@@ -207,7 +206,7 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
                 to_insert = set()
 
                 if is_public:
-                    for user_id in user_ids:
+                    for user_id in users_with_profile:
                         if self.get_if_app_services_interested_in_user(user_id):
                             continue
 
@@ -217,14 +216,14 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
                         await self.add_users_in_public_rooms(room_id, to_insert)
                         to_insert.clear()
                 else:
-                    for user_id in user_ids:
+                    for user_id in users_with_profile:
                         if not self.hs.is_mine_id(user_id):
                             continue
 
                         if self.get_if_app_services_interested_in_user(user_id):
                             continue
 
-                        for other_user_id in user_ids:
+                        for other_user_id in users_with_profile:
                             if user_id == other_user_id:
                                 continue