closes #4101

public/language/en_GB/topic.json

@@ -43,6 +43,7 @@
 
 	"markAsUnreadForAll.success" : "Topic marked as unread for all.",
 	"mark_unread": "Mark unread",
+	"mark_unread.success": "Topic marked as unread.",
 
 	"watch": "Watch",
 	"unwatch": "Unwatch",

public/src/client/topic/threadTools.js

@@ -54,7 +54,12 @@ define('forum/topic/threadTools', [
 		});
 
 		topicContainer.on('click', '[component="topic/mark-unread"]', function() {
-			socket.emit('topics.markUnread', tid);
+			socket.emit('topics.markUnread', tid, function(err) {
+				if (err) {
+					return app.alertError(err);
+				}
+				app.alertSuccess('[[topic:mark_unread.success]]');
+			});
 			return false;
 		});
 

src/socket.io/topics/unread.js

@@ -56,7 +56,7 @@ module.exports = function(SocketTopics) {
 
 	SocketTopics.markUnread = function(socket, tid, callback) {
 		if (!tid || !socket.uid) {
-			return callback();
+			return callback(new Error('[[error:invalid-data]]'));
 		}
 		topics.markUnread(tid, socket.uid, function(err) {
 			if (err) {
@@ -64,6 +64,7 @@ module.exports = function(SocketTopics) {
 			}
 
 			topics.pushUnreadCount(socket.uid);
+			callback();
 		});
 	};