Add transaction id to roomserver output API

src/github.com/matrix-org/dendrite/roomserver/api/output.go

@@ -107,6 +107,9 @@ type OutputNewRoomEvent struct {
 	// We encode the server name that the event should be sent using here to
 	// future proof the API for virtual hosting.
 	SendAsServer string `json:"send_as_server"`
+	// The transaction ID of the send request if sent by a local user and one
+	// was specified
+	TransactionID *TransactionID `json:"transaction_id"`
 }
 
 // An OutputNewInviteEvent is written whenever an invite becomes active.

src/github.com/matrix-org/dendrite/roomserver/input/events.go

@@ -129,7 +129,7 @@ func processRoomEvent(
 	}
 
 	// Update the extremities of the event graph for the room
-	return updateLatestEvents(ctx, db, ow, roomNID, stateAtEvent, event, input.SendAsServer)
+	return updateLatestEvents(ctx, db, ow, roomNID, stateAtEvent, event, input.SendAsServer, input.TransactionID)
 }
 
 func processInviteEvent(

src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go

@@ -50,6 +50,7 @@ func updateLatestEvents(
 	stateAtEvent types.StateAtEvent,
 	event gomatrixserverlib.Event,
 	sendAsServer string,
+	transactionID *api.TransactionID,
 ) (err error) {
 	updater, err := db.GetLatestEventsForUpdate(ctx, roomNID)
 	if err != nil {
@@ -61,6 +62,7 @@ func updateLatestEvents(
 	u := latestEventsUpdater{
 		ctx: ctx, db: db, updater: updater, ow: ow, roomNID: roomNID,
 		stateAtEvent: stateAtEvent, event: event, sendAsServer: sendAsServer,
+		transactionID: transactionID,
 	}
 	if err = u.doUpdateLatestEvents(); err != nil {
 		return err
@@ -75,13 +77,14 @@ func updateLatestEvents(
 // The state could be passed using function arguments, but it becomes impractical
 // when there are so many variables to pass around.
 type latestEventsUpdater struct {
-	ctx          context.Context
-	db           RoomEventDatabase
-	updater      types.RoomRecentEventsUpdater
-	ow           OutputRoomEventWriter
-	roomNID      types.RoomNID
-	stateAtEvent types.StateAtEvent
-	event        gomatrixserverlib.Event
+	ctx           context.Context
+	db            RoomEventDatabase
+	updater       types.RoomRecentEventsUpdater
+	ow            OutputRoomEventWriter
+	roomNID       types.RoomNID
+	stateAtEvent  types.StateAtEvent
+	event         gomatrixserverlib.Event
+	transactionID *api.TransactionID
 	// Which server to send this event as.
 	sendAsServer string
 	// The eventID of the event that was processed before this one.
@@ -241,6 +244,7 @@ func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error)
 		Event:           u.event,
 		LastSentEventID: u.lastEventIDSent,
 		LatestEventIDs:  latestEventIDs,
+		TransactionID:   u.transactionID,
 	}
 
 	var stateEventNIDs []types.EventNID