Go back to QueryMembershipsForRoom because appservices are hard

appservice/consumers/roomserver.go

@@ -17,7 +17,6 @@ package consumers
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 
 	"github.com/matrix-org/dendrite/appservice/storage"
 	"github.com/matrix-org/dendrite/appservice/types"
@@ -134,16 +133,26 @@ func (s *OutputRoomEventConsumer) appserviceJoinedAtEvent(ctx context.Context, e
 	// the event in question. Pretty sure this is what Synapse does too, but
 	// until we have a lighter way of checking the state before the event that
 	// doesn't involve state res, then this is probably OK.
-	membershipReq := &api.QueryMembershipForUserRequest{
+	membershipReq := &api.QueryMembershipsForRoomRequest{
-		RoomID: event.RoomID(),
+		RoomID:     event.RoomID(),
-		UserID: fmt.Sprintf("@%s:%s", appservice.SenderLocalpart, s.serverName),
+		JoinedOnly: true,
 	}
-	membershipRes := &api.QueryMembershipForUserResponse{}
+	membershipRes := &api.QueryMembershipsForRoomResponse{}
 
 	// XXX: This could potentially race if the state for the event is not known yet
 	// e.g. the event came over federation but we do not have the full state persisted.
-	if err := s.rsAPI.QueryMembershipForUser(ctx, membershipReq, membershipRes); err == nil {
+	if err := s.rsAPI.QueryMembershipsForRoom(ctx, membershipReq, membershipRes); err == nil {
-		return membershipRes.IsInRoom
+		for _, ev := range membershipRes.JoinEvents {
+			if ev.Type == gomatrixserverlib.MRoomMember {
+				var membership gomatrixserverlib.MemberContent
+				if err = json.Unmarshal(ev.Content, &membership); err != nil || ev.StateKey == nil {
+					continue
+				}
+				if membership.Membership == gomatrixserverlib.Join && appservice.IsInterestedInUserID(*ev.StateKey) {
+					return true
+				}
+			}
+		}
 	} else {
 		log.WithFields(log.Fields{
 			"room_id": event.RoomID(),

roomserver/internal/query/query.go

@@ -243,6 +243,24 @@ func (r *Queryer) QueryMembershipsForRoom(
 		return err
 	}
 
+	if request.Sender == "" {
+		var events []types.Event
+		var eventNIDs []types.EventNID
+		eventNIDs, err = r.DB.GetMembershipEventNIDsForRoom(ctx, info.RoomNID, request.JoinedOnly, false)
+		if err != nil {
+			return fmt.Errorf("r.DB.GetMembershipEventNIDsForRoom: %w", err)
+		}
+		events, err = r.DB.Events(ctx, eventNIDs)
+		if err != nil {
+			return fmt.Errorf("r.DB.Events: %w", err)
+		}
+		for _, event := range events {
+			clientEvent := gomatrixserverlib.ToClientEvent(event.Event, gomatrixserverlib.FormatAll)
+			response.JoinEvents = append(response.JoinEvents, clientEvent)
+		}
+		return nil
+	}
+
 	membershipEventNID, stillInRoom, isRoomforgotten, err := r.DB.GetMembership(ctx, info.RoomNID, request.Sender)
 	if err != nil {
 		return err