Add request to add a new playlist item

osu.Game/Online/Multiplayer/MatchUserRequest.cs

@@ -4,6 +4,7 @@
 using System;
 using MessagePack;
 using osu.Game.Online.Multiplayer.MatchTypes.TeamVersus;
+using osu.Game.Online.Multiplayer.Queueing;
 
 namespace osu.Game.Online.Multiplayer
 {
@@ -13,6 +14,7 @@ namespace osu.Game.Online.Multiplayer
     [Serializable]
     [MessagePackObject]
     [Union(0, typeof(ChangeTeamRequest))] // IMPORTANT: Add rules to SignalRUnionWorkaroundResolver for new derived types.
+    [Union(1, typeof(AddPlaylistItemRequest))]
     public abstract class MatchUserRequest
     {
     }

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -11,7 +11,6 @@ using System.Threading;
 using System.Threading.Tasks;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
-using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Graphics;
 using osu.Framework.Logging;
 using osu.Game.Beatmaps;
@@ -212,39 +211,18 @@ namespace osu.Game.Online.Multiplayer
         /// <param name="name">The new room name, if any.</param>
         /// <param name="password">The new password, if any.</param>
         /// <param name="matchType">The type of the match, if any.</param>
-        /// <param name="item">The new room playlist item, if any.</param>
         /// <param name="queueMode">The new queue mode, if any.</param>
-        public Task ChangeSettings(Optional<string> name = default, Optional<string> password = default, Optional<MatchType> matchType = default, Optional<PlaylistItem> item = default,
+        public Task ChangeSettings(Optional<string> name = default, Optional<string> password = default, Optional<MatchType> matchType = default, Optional<QueueModes> queueMode = default)
-                                   Optional<QueueModes> queueMode = default)
         {
             if (Room == null)
                 throw new InvalidOperationException("Must be joined to a match to change settings.");
 
-            // A dummy playlist item filled with the current room settings (except mods).
-            var existingPlaylistItem = new PlaylistItem
-            {
-                Beatmap =
-                {
-                    Value = new BeatmapInfo
-                    {
-                        OnlineBeatmapID = Room.Settings.BeatmapID,
-                        MD5Hash = Room.Settings.BeatmapChecksum
-                    }
-                },
-                RulesetID = Room.Settings.RulesetID
-            };
-
             return ChangeSettings(new MultiplayerRoomSettings
             {
                 Name = name.GetOr(Room.Settings.Name),
                 Password = password.GetOr(Room.Settings.Password),
-                BeatmapID = item.GetOr(existingPlaylistItem).BeatmapID,
-                BeatmapChecksum = item.GetOr(existingPlaylistItem).Beatmap.Value.MD5Hash,
-                RulesetID = item.GetOr(existingPlaylistItem).RulesetID,
                 MatchType = matchType.GetOr(Room.Settings.MatchType),
                 QueueMode = queueMode.GetOr(Room.Settings.QueueMode),
-                RequiredMods = item.HasValue ? item.Value.AsNonNull().RequiredMods.Select(m => new APIMod(m)).ToList() : Room.Settings.RequiredMods,
-                AllowedMods = item.HasValue ? item.Value.AsNonNull().AllowedMods.Select(m => new APIMod(m)).ToList() : Room.Settings.AllowedMods,
             });
         }
 

osu.Game/Online/Multiplayer/Queueing/AddPlaylistItemRequest.cs

@@ -0,0 +1,30 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+#nullable enable
+
+using System.Collections.Generic;
+using System.Linq;
+using MessagePack;
+using osu.Game.Online.API;
+
+namespace osu.Game.Online.Multiplayer.Queueing
+{
+    public class AddPlaylistItemRequest : MatchUserRequest
+    {
+        [Key(0)]
+        public int BeatmapID { get; set; }
+
+        [Key(1)]
+        public int RulesetID { get; set; }
+
+        [Key(2)]
+        public string BeatmapChecksum { get; set; } = string.Empty;
+
+        [Key(3)]
+        public IEnumerable<APIMod> RequiredMods { get; set; } = Enumerable.Empty<APIMod>();
+
+        [Key(4)]
+        public IEnumerable<APIMod> AllowedMods { get; set; } = Enumerable.Empty<APIMod>();
+    }
+}

osu.Game/Online/SignalRUnionWorkaroundResolver.cs

@@ -8,6 +8,7 @@ using MessagePack.Formatters;
 using MessagePack.Resolvers;
 using osu.Game.Online.Multiplayer;
 using osu.Game.Online.Multiplayer.MatchTypes.TeamVersus;
+using osu.Game.Online.Multiplayer.Queueing;
 
 namespace osu.Game.Online
 {
@@ -25,6 +26,7 @@ namespace osu.Game.Online
             { typeof(TeamVersusUserState), new TypeRedirectingFormatter<TeamVersusUserState, MatchUserState>() },
             { typeof(TeamVersusRoomState), new TypeRedirectingFormatter<TeamVersusRoomState, MatchRoomState>() },
             { typeof(ChangeTeamRequest), new TypeRedirectingFormatter<ChangeTeamRequest, MatchUserRequest>() },
+            { typeof(AddPlaylistItemRequest), new TypeRedirectingFormatter<AddPlaylistItemRequest, MatchUserRequest>() },
 
             // These should not be required. The fallback should work. But something is weird with the way caching is done.
             // For future adventurers, I would not advise looking into this further. It's likely not worth the effort.

osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSongSelect.cs

@@ -1,12 +1,15 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Logging;
 using osu.Framework.Screens;
 using osu.Game.Beatmaps;
 using osu.Game.Graphics.UserInterface;
+using osu.Game.Online.API;
 using osu.Game.Online.Multiplayer;
+using osu.Game.Online.Multiplayer.Queueing;
 using osu.Game.Online.Rooms;
 using osu.Game.Rulesets;
 using osu.Game.Rulesets.Mods;
@@ -54,7 +57,14 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
             {
                 loadingLayer.Show();
 
-                client.ChangeSettings(item: item).ContinueWith(t =>
+                client.SendMatchRequest(new AddPlaylistItemRequest
+                {
+                    BeatmapID = item.BeatmapID,
+                    RulesetID = item.RulesetID,
+                    BeatmapChecksum = item.Beatmap.Value.MD5Hash,
+                    RequiredMods = item.RequiredMods.Select(m => new APIMod(m)).ToArray(),
+                    AllowedMods = item.AllowedMods.Select(m => new APIMod(m)).ToArray()
+                }).ContinueWith(t =>
                 {
                     Schedule(() =>
                     {