From 1c6bd5fa800b1daaa0c02757d5e92dcd0ff33451 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Thu, 24 Sep 2020 15:33:17 +0100
Subject: [PATCH] Distinguish between room not existing and room being
 abandoned on this server

---
 federationapi/routing/join.go      | 8 +++++++-
 roomserver/api/query.go            | 2 ++
 roomserver/internal/query/query.go | 3 ++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/federationapi/routing/join.go b/federationapi/routing/join.go
index ef03f7a74..68cf86193 100644
--- a/federationapi/routing/join.go
+++ b/federationapi/routing/join.go
@@ -89,10 +89,16 @@ func MakeJoin(
 		util.GetLogger(httpReq.Context()).WithError(err).Error("rsAPI.QueryServerJoinedToRoom failed")
 		return jsonerror.InternalServerError()
 	}
+	if !inRoomRes.RoomExists {
+		return util.JSONResponse{
+			Code: http.StatusNotFound,
+			JSON: jsonerror.NotFound(fmt.Sprintf("Room ID %q was not found on this server", roomID)),
+		}
+	}
 	if !inRoomRes.IsInRoom {
 		return util.JSONResponse{
 			Code: http.StatusNotFound,
-			JSON: jsonerror.NotFound("There are no remaining users in this room"),
+			JSON: jsonerror.NotFound(fmt.Sprintf("Room ID %q has no remaining users on this server", roomID)),
 		}
 	}
 
diff --git a/roomserver/api/query.go b/roomserver/api/query.go
index 4b784a21f..5d61e862c 100644
--- a/roomserver/api/query.go
+++ b/roomserver/api/query.go
@@ -150,6 +150,8 @@ type QueryServerJoinedToRoomRequest struct {
 
 // QueryMembershipsForRoomResponse is a response to QueryServerJoinedToRoom
 type QueryServerJoinedToRoomResponse struct {
+	// True if the room exists on the server
+	RoomExists bool `json:"room_exists"`
 	// True if we still believe that we are participating in the room
 	IsInRoom bool `json:"is_in_room"`
 }
diff --git a/roomserver/internal/query/query.go b/roomserver/internal/query/query.go
index ec89df749..58cb44933 100644
--- a/roomserver/internal/query/query.go
+++ b/roomserver/internal/query/query.go
@@ -237,9 +237,10 @@ func (r *Queryer) QueryServerJoinedToRoom(
 	if err != nil {
 		return fmt.Errorf("r.DB.RoomInfo: %w", err)
 	}
-	if info == nil {
+	if info == nil || info.IsStub {
 		return nil
 	}
+	response.RoomExists = true
 
 	eventNIDs, err := r.DB.GetMembershipEventNIDsForRoom(ctx, info.RoomNID, true, false)
 	if err != nil {