bugfix: ensure newly joined live-stream rooms don't cause 500s

This was caused by the GlobalCache not having a metadata entry for
the new room, which in some cases prevented a stub from being made.

With regression test.

sync3/caches/user.go

@@ -372,7 +372,7 @@ func (c *UserCache) newRoomUpdate(roomID string) RoomUpdate {
 	u := c.LoadRoomData(roomID)
 	var r *internal.RoomMetadata
 	globalRooms := c.globalCache.LoadRooms(roomID)
-	if globalRooms == nil {
+	if globalRooms == nil || globalRooms[roomID] == nil {
 		// this can happen when we join a room we didn't know about because we process unread counts
 		// before the timeline events. Warn and send a stub
 		logger.Warn().Str("room", roomID).Msg("UserCache update: room doesn't exist in global cache yet, generating stub")
@@ -382,6 +382,7 @@ func (c *UserCache) newRoomUpdate(roomID string) RoomUpdate {
 	} else {
 		r = globalRooms[roomID]
 	}
+	internal.Assert("missing global room metadata for room "+roomID, r != nil)
 	return &roomUpdateCache{
 		roomID:         roomID,
 		globalRoomData: r,

sync3/handler/connstate.go

@@ -401,8 +401,10 @@ func (s *ConnState) OnRoomUpdate(up caches.RoomUpdate) {
 				return
 			}
 		}
+		internal.Assert("missing global room metadata", update.GlobalRoomMetadata() != nil)
 		s.live.onUpdate(update)
 	case caches.RoomUpdate:
+		internal.Assert("missing global room metadata", update.GlobalRoomMetadata() != nil)
 		s.live.onUpdate(update)
 	default:
 		logger.Warn().Str("room_id", up.RoomID()).Msg("OnRoomUpdate unknown update type")

sync3/sort.go

@@ -206,6 +206,7 @@ func (f *FilteredSortableRooms) Add(r RoomConnMetadata) bool {
 }
 
 func (f *FilteredSortableRooms) UpdateGlobalRoomMetadata(r *internal.RoomMetadata) int {
+	internal.Assert("missing room metadata", r != nil)
 	index, ok := f.SortableRooms.IndexOf(r.RoomID)
 	if !ok {
 		return -1

tests-e2e/lists_test.go

@@ -502,3 +502,49 @@ func TestMultipleOverlappingLists(t *testing.T) {
 		}),
 	)
 }
+
+// Regression test for a panic when new rooms were live-streamed to the client in Element-Web
+func TestNot500OnNewRooms(t *testing.T) {
+	boolTrue := true
+	boolFalse := false
+	mSpace := "m.space"
+	alice := registerNewUser(t)
+	res := alice.SlidingSync(t, sync3.Request{
+		Lists: []sync3.RequestList{
+			{
+				SlowGetAllRooms: &boolTrue,
+				Filters: &sync3.RequestFilters{
+					RoomTypes: []*string{&mSpace},
+				},
+			},
+		},
+	})
+	alice.CreateRoom(t, map[string]interface{}{"preset": "public_chat"})
+	alice.SlidingSync(t, sync3.Request{
+		Lists: []sync3.RequestList{
+			{
+				SlowGetAllRooms: &boolTrue,
+				Filters: &sync3.RequestFilters{
+					RoomTypes: []*string{&mSpace},
+				},
+			},
+			{
+				Filters: &sync3.RequestFilters{
+					IsDM: &boolFalse,
+				},
+				Ranges: sync3.SliceRanges{{0, 20}},
+			},
+		},
+	}, WithPos(res.Pos))
+	alice.CreateRoom(t, map[string]interface{}{"preset": "public_chat"})
+	alice.SlidingSync(t, sync3.Request{
+		Lists: []sync3.RequestList{
+			{
+				SlowGetAllRooms: &boolTrue,
+			},
+			{
+				Ranges: sync3.SliceRanges{{0, 20}},
+			},
+		},
+	}, WithPos(res.Pos))
+}

testutils/event.go

@@ -63,6 +63,13 @@ func NewJoinEvent(t TestBenchInterface, userID string, modifiers ...eventMockMod
 	}, modifiers...)
 }
 
+func NewMessageEvent(t TestBenchInterface, userID, text string) json.RawMessage {
+	return NewEvent(t, "m.room.message", userID, map[string]interface{}{
+		"msgtype": "m.text",
+		"body":    text,
+	})
+}
+
 func NewStateEvent(t TestBenchInterface, evType, stateKey, sender string, content interface{}, modifiers ...eventMockModifier) json.RawMessage {
 	t.Helper()
 	e := &eventMock{