Don't transfer MD5 hashes in collections when copying beatmaps

Fixes #22306.

Changes beatmap saving so that by default it does not transfer
the hashes in collections, and only transfers them when saving the same
difficulty in the editor.

Issue seems to have been introduced in https://github.com/ppy/osu/pull/20641.

osu.Game.Tests/Visual/Editing/TestSceneEditorBeatmapCreation.cs

@@ -13,6 +13,7 @@ using osu.Framework.Screens;
 using osu.Framework.Testing;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.ControlPoints;
+using osu.Game.Collections;
 using osu.Game.Database;
 using osu.Game.Overlays.Dialog;
 using osu.Game.Rulesets;
@@ -42,6 +43,9 @@ namespace osu.Game.Tests.Visual.Editing
         [Resolved]
         private BeatmapManager beatmapManager { get; set; } = null!;
 
+        [Resolved]
+        private RealmAccess realm { get; set; } = null!;
+
         private Guid currentBeatmapSetID => EditorBeatmap.BeatmapInfo.BeatmapSet?.ID ?? Guid.Empty;
 
         public override void SetUpSteps()
@@ -224,7 +228,8 @@ namespace osu.Game.Tests.Visual.Editing
                 return beatmap != null
                        && beatmap.DifficultyName == secondDifficultyName
                        && set != null
-                       && set.PerformRead(s => s.Beatmaps.Count == 2 && s.Beatmaps.Any(b => b.DifficultyName == secondDifficultyName) && s.Beatmaps.All(b => s.Status == BeatmapOnlineStatus.LocallyModified));
+                       && set.PerformRead(s =>
+                           s.Beatmaps.Count == 2 && s.Beatmaps.Any(b => b.DifficultyName == secondDifficultyName) && s.Beatmaps.All(b => s.Status == BeatmapOnlineStatus.LocallyModified));
             });
         }
 
@@ -327,6 +332,56 @@ namespace osu.Game.Tests.Visual.Editing
             AddAssert("old beatmap file not deleted", () => refetchedBeatmapSet.AsNonNull().PerformRead(s => s.Files.Count == 2));
         }
 
+        [Test]
+        public void TestCopyDifficultyDoesNotChangeCollections()
+        {
+            string originalDifficultyName = Guid.NewGuid().ToString();
+
+            AddStep("set unique difficulty name", () => EditorBeatmap.BeatmapInfo.DifficultyName = originalDifficultyName);
+            AddStep("save beatmap", () => Editor.Save());
+
+            string originalMd5 = string.Empty;
+            BeatmapCollection collection = null!;
+
+            AddStep("setup a collection with original beatmap", () =>
+            {
+                collection = new BeatmapCollection("test copy");
+                collection.BeatmapMD5Hashes.Add(originalMd5 = EditorBeatmap.BeatmapInfo.MD5Hash);
+
+                realm.Write(r =>
+                {
+                    r.Add(collection);
+                });
+            });
+
+            AddAssert("collection contains original beatmap", () =>
+                !string.IsNullOrEmpty(originalMd5) && collection.BeatmapMD5Hashes.Contains(originalMd5));
+
+            AddStep("create new difficulty", () => Editor.CreateNewDifficulty(new OsuRuleset().RulesetInfo));
+
+            AddUntilStep("wait for dialog", () => DialogOverlay.CurrentDialog is CreateNewDifficultyDialog);
+            AddStep("confirm creation as a copy", () => DialogOverlay.CurrentDialog.Buttons.ElementAt(1).TriggerClick());
+
+            AddUntilStep("wait for created", () =>
+            {
+                string? difficultyName = Editor.ChildrenOfType<EditorBeatmap>().SingleOrDefault()?.BeatmapInfo.DifficultyName;
+                return difficultyName != null && difficultyName != originalDifficultyName;
+            });
+
+            AddStep("save without changes", () => Editor.Save());
+
+            AddAssert("collection still points to old beatmap", () => !collection.BeatmapMD5Hashes.Contains(EditorBeatmap.BeatmapInfo.MD5Hash)
+                                                                      && collection.BeatmapMD5Hashes.Contains(originalMd5));
+
+            AddStep("clean up collection", () =>
+            {
+                realm.Write(r =>
+                {
+                    r.Remove(collection);
+                });
+            });
+        }
+
         [Test]
         public void TestCreateMultipleNewDifficultiesSucceeds()
         {

osu.Game/Beatmaps/BeatmapManager.cs

@@ -186,7 +186,10 @@ namespace osu.Game.Beatmaps
             targetBeatmapSet.Beatmaps.Add(newBeatmap.BeatmapInfo);
             newBeatmap.BeatmapInfo.BeatmapSet = targetBeatmapSet;
 
-            Save(newBeatmap.BeatmapInfo, newBeatmap, beatmapSkin);
+            // make sure that collections don't get transferred when adding new difficulties to a set (that function
+            // was added for the scenario of saving the same difficulty), since this path is invoked from copying
+            // an existing difficulty as well.
+            Save(newBeatmap.BeatmapInfo, newBeatmap, beatmapSkin, false);
 
             workingBeatmapCache.Invalidate(targetBeatmapSet);
             return GetWorkingBeatmap(newBeatmap.BeatmapInfo);
@@ -285,7 +288,8 @@ namespace osu.Game.Beatmaps
         /// <param name="beatmapInfo">The <see cref="BeatmapInfo"/> to save the content against. The file referenced by <see cref="BeatmapInfo.Path"/> will be replaced.</param>
         /// <param name="beatmapContent">The <see cref="IBeatmap"/> content to write.</param>
         /// <param name="beatmapSkin">The beatmap <see cref="ISkin"/> content to write, null if to be omitted.</param>
-        public virtual void Save(BeatmapInfo beatmapInfo, IBeatmap beatmapContent, ISkin? beatmapSkin = null)
+        /// <param name="transferCollections">Whether to transfer the MD5 hashes in collections referencing this beatmap.</param>
+        public virtual void Save(BeatmapInfo beatmapInfo, IBeatmap beatmapContent, ISkin? beatmapSkin = null, bool transferCollections = false)
         {
             var setInfo = beatmapInfo.BeatmapSet;
             Debug.Assert(setInfo != null);
@@ -337,7 +341,8 @@ namespace osu.Game.Beatmaps
 
                     setInfo.CopyChangesToRealm(liveBeatmapSet);
 
-                    beatmapInfo.TransferCollectionReferences(r, oldMd5Hash);
+                    if (transferCollections)
+                        beatmapInfo.TransferCollectionReferences(r, oldMd5Hash);
 
                     ProcessBeatmap?.Invoke((liveBeatmapSet, false));
                 });

osu.Game/Screens/Edit/Editor.cs

@@ -429,7 +429,7 @@ namespace osu.Game.Screens.Edit
             try
             {
                 // save the loaded beatmap's data stream.
-                beatmapManager.Save(editorBeatmap.BeatmapInfo, editorBeatmap.PlayableBeatmap, editorBeatmap.BeatmapSkin);
+                beatmapManager.Save(editorBeatmap.BeatmapInfo, editorBeatmap.PlayableBeatmap, editorBeatmap.BeatmapSkin, true);
             }
             catch (Exception ex)
             {

osu.Game/Tests/Visual/EditorTestScene.cs

@@ -178,7 +178,7 @@ namespace osu.Game.Tests.Visual
                     => testBeatmapManager.TestBeatmap;
             }
 
-            public override void Save(BeatmapInfo info, IBeatmap beatmapContent, ISkin beatmapSkin = null)
+            public override void Save(BeatmapInfo info, IBeatmap beatmapContent, ISkin beatmapSkin = null, bool transferCollections = false)
             {
                 // don't actually care about saving for this context.
             }