From 44002e033fa57e2fa5115d4be04e7afbcd8981f9 Mon Sep 17 00:00:00 2001
From: Till Faelligen <2353100+S7evinK@users.noreply.github.com>
Date: Mon, 26 Sep 2022 13:53:00 +0200
Subject: [PATCH] Add join response if we're actually joined to the room

---
 syncapi/streams/stream_notificationdata.go | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/syncapi/streams/stream_notificationdata.go b/syncapi/streams/stream_notificationdata.go
index c789d7a23..1f178f4d0 100644
--- a/syncapi/streams/stream_notificationdata.go
+++ b/syncapi/streams/stream_notificationdata.go
@@ -3,6 +3,8 @@ package streams
 import (
 	"context"
 
+	"github.com/matrix-org/gomatrixserverlib"
+
 	"github.com/matrix-org/dendrite/syncapi/types"
 )
 
@@ -39,12 +41,17 @@ func (p *NotificationDataStreamProvider) IncrementalSync(
 		return from
 	}
 
-	// We're merely decorating existing rooms.
-	for roomID, jr := range req.Response.Rooms.Join {
-		counts := countsByRoom[roomID]
-		if counts == nil {
+	// Add notification data based on the membership of the user
+	for roomID, counts := range countsByRoom {
+		if req.Rooms[roomID] != gomatrixserverlib.Join {
 			continue
 		}
+		// If there's no join response, add a new one
+		jr, ok := req.Response.Rooms.Join[roomID]
+		if !ok {
+			jr = *types.NewJoinResponse()
+		}
+
 		jr.UnreadNotifications = &types.UnreadNotifications{
 			HighlightCount:    counts.UnreadHighlightCount,
 			NotificationCount: counts.UnreadNotificationCount,