Don't send account data or receipts for left/forgotten rooms (#2382)

* Only include account data and receipts for rooms in a complete sync that we care about

* Fix global account data

syncapi/streams/stream_accountdata.go

@@ -53,6 +53,12 @@ func (p *AccountDataStreamProvider) IncrementalSync(
 
 	// Iterate over the rooms
 	for roomID, dataTypes := range dataTypes {
+		// For a complete sync, make sure we're only including this room if
+		// that room was present in the joined rooms.
+		if from == 0 && roomID != "" && !req.IsRoomPresent(roomID) {
+			continue
+		}
+
 		// Request the missing data from the database
 		for _, dataType := range dataTypes {
 			dataReq := userapi.QueryAccountDataRequest{

syncapi/streams/stream_receipt.go

@@ -62,6 +62,12 @@ func (p *ReceiptStreamProvider) IncrementalSync(
 	}
 
 	for roomID, receipts := range receiptsByRoom {
+		// For a complete sync, make sure we're only including this room if
+		// that room was present in the joined rooms.
+		if from == 0 && !req.IsRoomPresent(roomID) {
+			continue
+		}
+
 		jr := *types.NewJoinResponse()
 		if existing, ok := req.Response.Rooms.Join[roomID]; ok {
 			jr = existing

syncapi/types/provider.go

@@ -25,6 +25,23 @@ type SyncRequest struct {
 	IgnoredUsers IgnoredUsers
 }
 
+func (r *SyncRequest) IsRoomPresent(roomID string) bool {
+	membership, ok := r.Rooms[roomID]
+	if !ok {
+		return false
+	}
+	switch membership {
+	case gomatrixserverlib.Join:
+		return true
+	case gomatrixserverlib.Invite:
+		return true
+	case gomatrixserverlib.Peek:
+		return true
+	default:
+		return false
+	}
+}
+
 type StreamProvider interface {
 	Setup()