Add sanity check to ensure we don't accidentally proliferate rooms

This small check just ensures that we aren't about to blindly accept that the calling code knows what it is doing. There are some unknown cases where NewRoom gets fired for rooms we already know about, so in those cases we just change it to a PossibleTagChange which is what the caller likely intended. 

Many of the edge cases are unknown, though this can happen for an invite being accepted (for example). It's easier to handle it here instead of tracking down every single possibility and fixing it higher up.

Author: turt2live

src/stores/room-list/algorithms/Algorithm.ts

@@ -587,6 +587,14 @@ export class Algorithm extends EventEmitter {
     public async handleRoomUpdate(room: Room, cause: RoomUpdateCause): Promise<boolean> {
         if (!this.algorithms) throw new Error("Not ready: no algorithms to determine tags from");
 
+        if (cause === RoomUpdateCause.NewRoom) {
+            const roomTags = this.roomIdsToTags[room.roomId];
+            if (roomTags && roomTags.length > 0) {
+                console.warn(`${room.roomId} is reportedly new but is already known - assuming TagChange instead`);
+                cause = RoomUpdateCause.PossibleTagChange;
+            }
+        }
+
         if (cause === RoomUpdateCause.PossibleTagChange) {
             // TODO: Be smarter and splice rather than regen the planet. https://github.com/vector-im/riot-web/issues/14035
             // TODO: No-op if no change. https://github.com/vector-im/riot-web/issues/14035