Implement MSC3946 for getRoomUpgradeHistory

Author: andybalaam

spec/unit/matrix-client.spec.ts

@@ -2458,6 +2458,52 @@ describe("MatrixClient", function () {
                 return [room1, room2, room3, room4];
             }
 
+            /**
+             * Creates 2 alternate chains of room history: one using create
+             * events, and one using MSC2946 predecessor+tombstone events.
+             *
+             * Using create, history looks like:
+             * room1->room2->room3->room4 (but note we do not create tombstones)
+             *
+             * Using predecessor+tombstone, history looks like:
+             * dynRoom1->dynRoom2->room3->dynRoom4->dynRoom4
+             *
+             * @returns [room1, room2, room3, room4, dynRoom1, dynRoom2,
+             *          dynRoom4, dynRoom5].
+             */
+            function createDynamicRoomHistory(): [Room, Room, Room, Room, Room, Room, Room, Room] {
+                // Don't create tombstones for the old versions - we generally
+                // expect only one tombstone in a room, and we are confused by
+                // anything else.
+                const creates = true;
+                const tombstones = false;
+                const [room1, room2, room3, room4] = createRoomHistory(creates, tombstones);
+                const dynRoom1 = new Room("dynRoom1", client, "@rick:grimes.example.com");
+                const dynRoom2 = new Room("dynRoom2", client, "@rick:grimes.example.com");
+                const dynRoom4 = new Room("dynRoom4", client, "@rick:grimes.example.com");
+                const dynRoom5 = new Room("dynRoom5", client, "@rick:grimes.example.com");
+
+                dynRoom1.addLiveEvents([tombstoneEvent(dynRoom2.roomId, dynRoom1.roomId)], {});
+                dynRoom2.addLiveEvents([predecessorEvent(dynRoom2.roomId, dynRoom1.roomId)]);
+
+                dynRoom2.addLiveEvents([tombstoneEvent(room3.roomId, dynRoom2.roomId)], {});
+                room3.addLiveEvents([predecessorEvent(room3.roomId, dynRoom2.roomId)]);
+
+                room3.addLiveEvents([tombstoneEvent(dynRoom4.roomId, room3.roomId)], {});
+                dynRoom4.addLiveEvents([predecessorEvent(dynRoom4.roomId, room3.roomId)]);
+
+                dynRoom4.addLiveEvents([tombstoneEvent(dynRoom5.roomId, dynRoom4.roomId)], {});
+                dynRoom5.addLiveEvents([predecessorEvent(dynRoom5.roomId, dynRoom4.roomId)]);
+
+                mocked(store.getRoom)
+                    .mockClear()
+                    .mockImplementation((roomId: string) => {
+                        return { room1, room2, room3, room4, dynRoom1, dynRoom2, dynRoom4, dynRoom5 }[roomId] || null;
+                    });
+
+                return [room1, room2, room3, room4, dynRoom1, dynRoom2, dynRoom4, dynRoom5];
+            }
+
             it("Returns an empty list if room does not exist", () => {
                 const history = client.getRoomUpgradeHistory("roomthatdoesnotexist");
                 expect(history).toHaveLength(0);
@@ -2600,6 +2646,30 @@ describe("MatrixClient", function () {
                     room4.roomId,
                 ]);
             });
+
+            it("Returns the predecessors and subsequent rooms using MSC3945 dynamic room predecessors", () => {
+                const [, , room3, , dynRoom1, dynRoom2, dynRoom4, dynRoom5] = createDynamicRoomHistory();
+                const useMsc3946 = true;
+                const verifyLinks = false;
+                const history = client.getRoomUpgradeHistory(room3.roomId, verifyLinks, useMsc3946);
+                expect(history.map((room) => room.roomId)).toEqual([
+                    dynRoom1.roomId,
+                    dynRoom2.roomId,
+                    room3.roomId,
+                    dynRoom4.roomId,
+                    dynRoom5.roomId,
+                ]);
+            });
+
+            it("When not asking for MSC3946, verified history without tombstones is empty", () => {
+                // There no tombstones to match the create events
+                const [, , room3] = createDynamicRoomHistory();
+                const useMsc3946 = false;
+                const verifyLinks = true;
+                const history = client.getRoomUpgradeHistory(room3.roomId, verifyLinks, useMsc3946);
+                // So we get no history back
+                expect(history.map((room) => room.roomId)).toEqual([room3.roomId]);
+            });
         });
     });
 });

src/client.ts

@@ -4990,24 +4990,31 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
      * which can be proven to be linked. For example, rooms which have a create
      * event pointing to an old room which the client is not aware of or doesn't
      * have a matching tombstone would not be returned.
+     * @param msc3946ProcessDynamicPredecessor - if true, look for
+     * m.room.predecessor state events as well as create events, and prefer
+     * predecessor events where they exist (MSC3946).
      * @returns An array of rooms representing the upgrade
      * history.
      */
-    public getRoomUpgradeHistory(roomId: string, verifyLinks = false): Room[] {
+    public getRoomUpgradeHistory(
+        roomId: string,
+        verifyLinks = false,
+        msc3946ProcessDynamicPredecessor = false,
+    ): Room[] {
         const currentRoom = this.getRoom(roomId);
         if (!currentRoom) return [];
 
-        const before = this.findPredecessorRooms(currentRoom, verifyLinks);
-        const after = this.findSuccessorRooms(currentRoom, verifyLinks);
+        const before = this.findPredecessorRooms(currentRoom, verifyLinks, msc3946ProcessDynamicPredecessor);
+        const after = this.findSuccessorRooms(currentRoom, verifyLinks, msc3946ProcessDynamicPredecessor);
 
         return [...before, currentRoom, ...after];
     }
 
-    private findPredecessorRooms(room: Room, verifyLinks: boolean): Room[] {
+    private findPredecessorRooms(room: Room, verifyLinks: boolean, msc3946ProcessDynamicPredecessor: boolean): Room[] {
         const ret: Room[] = [];
 
         // Work backwards from newer to older rooms
-        let predecessorRoomId = room.findPredecessorRoomId();
+        let predecessorRoomId = room.findPredecessorRoomId(msc3946ProcessDynamicPredecessor);
         while (predecessorRoomId !== null) {
             const predecessorRoom = this.getRoom(predecessorRoomId);
             if (predecessorRoom === null) {
@@ -5024,23 +5031,23 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             ret.splice(0, 0, predecessorRoom);
 
             room = predecessorRoom;
-            predecessorRoomId = room.findPredecessorRoomId();
+            predecessorRoomId = room.findPredecessorRoomId(msc3946ProcessDynamicPredecessor);
         }
         return ret;
     }
 
-    private findSuccessorRooms(room: Room, verifyLinks: boolean): Room[] {
+    private findSuccessorRooms(room: Room, verifyLinks: boolean, msc3946ProcessDynamicPredecessor: boolean): Room[] {
         const ret: Room[] = [];
 
         // Work forwards, looking at tombstone events
         let tombstoneEvent = room.currentState.getStateEvents(EventType.RoomTombstone, "");
         while (tombstoneEvent) {
             const successorRoom = this.getRoom(tombstoneEvent.getContent()["replacement_room"]);
             if (!successorRoom) break; // end of the chain
-            if (successorRoom.roomId === room.roomId) break; // Tombstone is referencing it's own room
+            if (successorRoom.roomId === room.roomId) break; // Tombstone is referencing its own room
 
             if (verifyLinks) {
-                const predecessorRoomId = successorRoom.findPredecessorRoomId();
+                const predecessorRoomId = successorRoom.findPredecessorRoomId(msc3946ProcessDynamicPredecessor);
                 if (!predecessorRoomId || predecessorRoomId !== room.roomId) {
                     break;
                 }