Examine all m.direct rooms to find a DM as fallback (#10127)

test/utils/dm/findDMForUser-test.ts

@@ -30,12 +30,15 @@ jest.mock("../../../src/utils/room/getFunctionalMembers", () => ({
 describe("findDMForUser", () => {
     const userId1 = "@user1:example.com";
     const userId2 = "@user2:example.com";
+    const userId3 = "@user3:example.com";
     const botId = "@bot:example.com";
     let room1: Room;
     let room2: LocalRoom;
     let room3: Room;
     let room4: Room;
     let room5: Room;
+    let room6: Room;
+    const room7Id = "!room7:example.com";
     let dmRoomMap: DMRoomMap;
     let mockClient: MatrixClient;
 
@@ -78,33 +81,56 @@ describe("findDMForUser", () => {
         room5 = new Room("!room5:example.com", mockClient, userId1);
         room5.getLastActiveTimestamp = () => 100;
 
+        // room not correctly stored in userId → room map; should be found by the "all rooms" fallback
+        room6 = new Room("!room6:example.com", mockClient, userId1);
+        room6.getMyMembership = () => "join";
+        room6.currentState.setStateEvents([
+            makeMembershipEvent(room6.roomId, userId1, "join"),
+            makeMembershipEvent(room6.roomId, userId3, "join"),
+        ]);
+
         mocked(mockClient.getRoom).mockImplementation((roomId: string) => {
-            return {
-                [room1.roomId]: room1,
-                [room2.roomId]: room2,
-                [room3.roomId]: room3,
-                [room4.roomId]: room4,
-                [room5.roomId]: room5,
-            }[roomId];
+            return (
+                {
+                    [room1.roomId]: room1,
+                    [room2.roomId]: room2,
+                    [room3.roomId]: room3,
+                    [room4.roomId]: room4,
+                    [room5.roomId]: room5,
+                    [room6.roomId]: room6,
+                }[roomId] || null
+            );
         });
 
         dmRoomMap = {
             getDMRoomForIdentifiers: jest.fn(),
             getDMRoomsForUserId: jest.fn(),
+            getRoomIds: jest.fn().mockReturnValue(
+                new Set([
+                    room1.roomId,
+                    room2.roomId,
+                    room3.roomId,
+                    room4.roomId,
+                    room5.roomId,
+                    room6.roomId,
+                    room7Id, // this room does not exist in client
+                ]),
+            ),
         } as unknown as DMRoomMap;
         jest.spyOn(DMRoomMap, "shared").mockReturnValue(dmRoomMap);
-        mocked(dmRoomMap.getDMRoomsForUserId).mockReturnValue([
-            room1.roomId,
-            room2.roomId,
-            room3.roomId,
-            room4.roomId,
-            room5.roomId,
-        ]);
+        mocked(dmRoomMap.getDMRoomsForUserId).mockImplementation((userId: string) => {
+            if (userId === userId1) {
+                return [room1.roomId, room2.roomId, room3.roomId, room4.roomId, room5.roomId, room7Id];
+            }
+
+            return [];
+        });
     });
 
     describe("for an empty DM room list", () => {
         beforeEach(() => {
             mocked(dmRoomMap.getDMRoomsForUserId).mockReturnValue([]);
+            mocked(dmRoomMap.getRoomIds).mockReturnValue(new Set());
         });
 
         it("should return undefined", () => {
@@ -125,4 +151,11 @@ describe("findDMForUser", () => {
 
         expect(findDMForUser(mockClient, userId1)).toBe(room3);
     });
+
+    it("should find a room by the 'all rooms' fallback", () => {
+        room1.getLastActiveTimestamp = () => 1;
+        room6.getLastActiveTimestamp = () => 2;
+
+        expect(findDMForUser(mockClient, userId3)).toBe(room6);
+    });
 });