Add IBeatmapSetInfo equality support

osu.Game/Beatmaps/BeatmapSetInfo.cs

@@ -66,6 +66,17 @@ namespace osu.Game.Beatmaps
 
         public bool Protected { get; set; }
 
+        public bool Equals(IBeatmapSetInfo other)
+        {
+            if (other is BeatmapSetInfo b)
+                return Equals(b);
+
+            if (OnlineID > 0 && other?.OnlineID > 0)
+                return other.OnlineID == OnlineID;
+
+            return false;
+        }
+
         public bool Equals(BeatmapSetInfo other)
         {
             if (other == null)

osu.Game/Beatmaps/IBeatmapSetInfo.cs

@@ -12,7 +12,7 @@ namespace osu.Game.Beatmaps
     /// <summary>
     /// A representation of a collection of beatmap difficulties, generally packaged as an ".osz" archive.
     /// </summary>
-    public interface IBeatmapSetInfo : IHasOnlineID<int>
+    public interface IBeatmapSetInfo : IHasOnlineID<int>, IEquatable<IBeatmapSetInfo>
     {
         /// <summary>
         /// The date when this beatmap was imported.

osu.Game/Models/RealmBeatmapSet.cs

@@ -53,7 +53,16 @@ namespace osu.Game.Models
         /// <param name="filename">The name of the file to get the storage path of.</param>
         public string? GetPathForFile(string filename) => Files.SingleOrDefault(f => string.Equals(f.Filename, filename, StringComparison.OrdinalIgnoreCase))?.File.StoragePath;
 
-        public override string ToString() => Metadata?.ToString() ?? base.ToString();
+        public bool Equals(IBeatmapSetInfo? other)
+        {
+            if (other is RealmBeatmap b)
+                return b.ID == ID;
+
+            if (OnlineID > 0 && other?.OnlineID > 0)
+                return other.OnlineID == OnlineID;
+
+            return false;
+        }
 
         public bool Equals(RealmBeatmapSet? other)
         {
@@ -72,6 +81,8 @@ namespace osu.Game.Models
             return ReferenceEquals(this, other);
         }
 
+        public override string ToString() => Metadata?.ToString() ?? base.ToString();
+
         IEnumerable<IBeatmapInfo> IBeatmapSetInfo.Beatmaps => Beatmaps;
 
         IEnumerable<INamedFileUsage> IBeatmapSetInfo.Files => Files;

osu.Game/Online/API/Requests/Responses/APIBeatmapSet.cs

@@ -141,5 +141,17 @@ namespace osu.Game.Online.API.Requests.Responses
         double IBeatmapSetInfo.MaxBPM => BPM;
 
         #endregion
+
+        #region Implementation of IEquatable<IBeatmapSetInfo>
+
+        public bool Equals(IBeatmapSetInfo? other)
+        {
+            if (OnlineID > 0 && other?.OnlineID > 0)
+                return other.OnlineID == OnlineID;
+
+            return false;
+        }
+
+        #endregion
     }
 }