Do not send alias events when creating / upgrading a room

changelog.d/6941.removal

@@ -0,0 +1 @@
+Stop sending m.room.aliases events during room creation and upgrade.

synapse/handlers/directory.py

@@ -282,22 +282,6 @@ def on_directory_query(self, args):
                 Codes.NOT_FOUND,
             )
 
-    @defer.inlineCallbacks
-    def send_room_alias_update_event(self, requester, room_id):
-        aliases = yield self.store.get_aliases_for_room(room_id)
-
-        yield self.event_creation_handler.create_and_send_nonmember_event(
-            requester,
-            {
-                "type": EventTypes.Aliases,
-                "state_key": self.hs.hostname,
-                "room_id": room_id,
-                "sender": requester.user.to_string(),
-                "content": {"aliases": aliases},
-            },
-            ratelimit=False,
-        )
-
     @defer.inlineCallbacks
     def _update_canonical_alias(self, requester, user_id, room_id, room_alias):
         """
@@ -326,7 +310,7 @@ def _update_canonical_alias(self, requester, user_id, room_id, room_alias):
         alt_aliases = content.pop("alt_aliases", None)
         # If the aliases are not a list (or not found) do not attempt to modify
         # the list.
-        if isinstance(alt_aliases, list):
+        if isinstance(alt_aliases, (list, tuple)):
             send_update = True
             alt_aliases = [alias for alias in alt_aliases if alias != alias_str]
             if alt_aliases:

synapse/handlers/room.py

@@ -456,11 +456,19 @@ def _move_aliases_to_new_room(
 
         # check to see if we have a canonical alias.
         canonical_alias = None
+        canonical_alt_aliases = []
         canonical_alias_event_id = old_room_state.get((EventTypes.CanonicalAlias, ""))
         if canonical_alias_event_id:
             canonical_alias_event = yield self.store.get_event(canonical_alias_event_id)
             if canonical_alias_event:
                 canonical_alias = canonical_alias_event.content.get("alias", "")
+                canonical_alt_aliases = canonical_alias_event.content.get(
+                    "alt_aliases", []
+                )
+                # If alt_aliases is not a list, overwrite it as whatever is there
+                # cannot be handled.
+                if not isinstance(canonical_alt_aliases, (list, tuple)):
+                    canonical_alt_aliases = []
 
         # first we try to remove the aliases from the old room (we suppress sending
         # the room_aliases event until the end).
@@ -488,19 +496,6 @@ def _move_aliases_to_new_room(
         if not removed_aliases:
             return
 
-        try:
-            # this can fail if, for some reason, our user doesn't have perms to send
-            # m.room.aliases events in the old room (note that we've already checked that
-            # they have perms to send a tombstone event, so that's not terribly likely).
-            #
-            # If that happens, it's regrettable, but we should carry on: it's the same
-            # as when you remove an alias from the directory normally - it just means that
-            # the aliases event gets out of sync with the directory
-            # (cf https://github.com/vector-im/riot-web/issues/2369)
-            yield directory_handler.send_room_alias_update_event(requester, old_room_id)
-        except AuthError as e:
-            logger.warning("Failed to send updated alias event on old room: %s", e)
-
         # we can now add any aliases we successfully removed to the new room.
         for alias in removed_aliases:
             try:
@@ -517,21 +512,30 @@ def _move_aliases_to_new_room(
                 # checking module decides it shouldn't, or similar.
                 logger.error("Error adding alias %s to new room: %s", alias, e)
 
+        # The canonical alias and alternative aliases can only be propagated to
+        # the new room if they were removed from the old room.
+        content = {}
+        if canonical_alias and (canonical_alias in removed_aliases):
+            content["alias"] = canonical_alias
+        canonical_alt_aliases = [
+            alias for alias in canonical_alt_aliases if alias in removed_aliases
+        ]
+        if canonical_alt_aliases:
+            content["alt_aliases"] = canonical_alt_aliases
+
         try:
-            if canonical_alias and (canonical_alias in removed_aliases):
+            if content:
                 yield self.event_creation_handler.create_and_send_nonmember_event(
                     requester,
                     {
                         "type": EventTypes.CanonicalAlias,
                         "state_key": "",
                         "room_id": new_room_id,
                         "sender": requester.user.to_string(),
-                        "content": {"alias": canonical_alias},
+                        "content": content,
                     },
                     ratelimit=False,
                 )
-
-            yield directory_handler.send_room_alias_update_event(requester, new_room_id)
         except SynapseError as e:
             # again I'm not really expecting this to fail, but if it does, I'd rather
             # we returned the new room to the client at this point.
@@ -757,7 +761,6 @@ def create_room(self, requester, config, ratelimit=True, creator_join_profile=No
 
         if room_alias:
             result["room_alias"] = room_alias.to_string()
-            yield directory_handler.send_room_alias_update_event(requester, room_id)
 
         return result