More invite support (#979)

* Update gomatixserverlib

* Try to build invite stripped state if not given to us

* SendInvite improvements

* Transpose invite_room_state into invite_state.events for sync API

* Remove syncapi debugging output

* Use RespInviteV2

* Update gomatrixserverlib

* Send the invite event as a normal roomserver event too, for incorporating into room (should this be done by the roomserver automatically for invite inputs?)

* Federation sender use invite_room_state, room server try to insert membership state

* Check supported room versions on the invite endpoint

* Prevent roomserver query API from trying to handle requests for stub rooms

* Adding a nolint

* Replace IsRoomStub with RoomNIDExcludingStubs, fix query API to use that instead

* Review comments

roomserver/input/events.go

@@ -196,8 +196,23 @@ func processInviteEvent(
 
 	event := input.Event.Unwrap()
 
-	if err = event.SetUnsignedField("invite_room_state", input.InviteRoomState); err != nil {
-		return err
+	if len(input.InviteRoomState) > 0 {
+		// If we were supplied with some invite room state already (which is
+		// most likely to be if the event came in over federation) then use
+		// that.
+		if err = event.SetUnsignedField("invite_room_state", input.InviteRoomState); err != nil {
+			return err
+		}
+	} else {
+		// There's no invite room state, so let's have a go at building it
+		// up from local data (which is most likely to be if the event came
+		// from the CS API). If we know about the room then we can insert
+		// the invite room state, if we don't then we just fail quietly.
+		if irs, ierr := buildInviteStrippedState(ctx, db, input); ierr == nil {
+			if err = event.SetUnsignedField("invite_room_state", irs); err != nil {
+				return err
+			}
+		}
 	}
 
 	outputUpdates, err := updateToInviteMembership(updater, &event, nil, input.Event.RoomVersion)
@@ -212,3 +227,50 @@ func processInviteEvent(
 	succeeded = true
 	return nil
 }
+
+func buildInviteStrippedState(
+	ctx context.Context,
+	db storage.Database,
+	input api.InputInviteEvent,
+) ([]gomatrixserverlib.InviteV2StrippedState, error) {
+	roomNID, err := db.RoomNID(ctx, input.Event.RoomID())
+	if err != nil || roomNID == 0 {
+		return nil, fmt.Errorf("room %q unknown", input.Event.RoomID())
+	}
+	stateWanted := []gomatrixserverlib.StateKeyTuple{}
+	for _, t := range []string{
+		gomatrixserverlib.MRoomName, gomatrixserverlib.MRoomCanonicalAlias,
+		gomatrixserverlib.MRoomAliases, gomatrixserverlib.MRoomJoinRules,
+	} {
+		stateWanted = append(stateWanted, gomatrixserverlib.StateKeyTuple{
+			EventType: t,
+			StateKey:  "",
+		})
+	}
+	_, currentStateSnapshotNID, _, err := db.LatestEventIDs(ctx, roomNID)
+	if err != nil {
+		return nil, err
+	}
+	roomState := state.NewStateResolution(db)
+	stateEntries, err := roomState.LoadStateAtSnapshotForStringTuples(
+		ctx, currentStateSnapshotNID, stateWanted,
+	)
+	if err != nil {
+		return nil, err
+	}
+	stateNIDs := []types.EventNID{}
+	for _, stateNID := range stateEntries {
+		stateNIDs = append(stateNIDs, stateNID.EventNID)
+	}
+	stateEvents, err := db.Events(ctx, stateNIDs)
+	if err != nil {
+		return nil, err
+	}
+	inviteState := []gomatrixserverlib.InviteV2StrippedState{
+		gomatrixserverlib.NewInviteV2StrippedState(&input.Event.Event),
+	}
+	for _, event := range stateEvents {
+		inviteState = append(inviteState, gomatrixserverlib.NewInviteV2StrippedState(&event.Event))
+	}
+	return inviteState, nil
+}

roomserver/input/membership.go

@@ -144,7 +144,7 @@ func updateToInviteMembership(
 		// consider a single stream of events when determining whether a user
 		// is invited, rather than having to combine multiple streams themselves.
 		onie := api.OutputNewInviteEvent{
-			Event:       (*add).Headered(roomVersion),
+			Event:       add.Headered(roomVersion),
 			RoomVersion: roomVersion,
 		}
 		updates = append(updates, api.OutputEvent{