Add failing tests for preserving clipboard content

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

@@ -71,6 +71,40 @@ namespace osu.Game.Tests.Visual.Editing
             AddAssert("stack empty", () => Stack.CurrentScreen == null);
         }
 
+        [Test]
+        public void TestClipboardPreservedAfterSwitch([Values] bool sameRuleset)
+        {
+            BeatmapInfo targetDifficulty = null;
+
+            AddStep("select first object", () => EditorBeatmap.SelectedHitObjects.Add(EditorBeatmap.HitObjects.First()));
+            AddStep("copy object", () => Editor.Copy());
+
+            AddStep("set target difficulty", () =>
+            {
+                targetDifficulty = sameRuleset
+                    ? importedBeatmapSet.Beatmaps.Last(beatmap => !beatmap.Equals(Beatmap.Value.BeatmapInfo) && beatmap.RulesetID == Beatmap.Value.BeatmapInfo.RulesetID)
+                    : importedBeatmapSet.Beatmaps.Last(beatmap => !beatmap.Equals(Beatmap.Value.BeatmapInfo) && beatmap.RulesetID != Beatmap.Value.BeatmapInfo.RulesetID);
+            });
+            switchToDifficulty(() => targetDifficulty);
+            confirmEditingBeatmap(() => targetDifficulty);
+
+            AddAssert("no objects selected", () => !EditorBeatmap.SelectedHitObjects.Any());
+            AddStep("paste object", () => Editor.Paste());
+
+            if (sameRuleset)
+                AddAssert("object was pasted", () => EditorBeatmap.SelectedHitObjects.Any());
+            else
+                AddAssert("object was not pasted", () => !EditorBeatmap.SelectedHitObjects.Any());
+
+            AddStep("exit editor", () => Stack.Exit());
+
+            AddUntilStep("prompt for save dialog shown", () => DialogOverlay.CurrentDialog is PromptForSaveDialog);
+            AddStep("discard changes", () => ((PromptForSaveDialog)DialogOverlay.CurrentDialog).PerformOkAction());
+
+            // ensure editor loader didn't resume.
+            AddAssert("stack empty", () => Stack.CurrentScreen == null);
+        }
+
         [Test]
         public void TestPreventSwitchDueToUnsavedChanges()
         {

osu.Game/Screens/Edit/Compose/ComposeScreen.cs

@@ -80,7 +80,7 @@ namespace osu.Game.Screens.Edit.Compose
         public bool OnPressed(PlatformAction action)
         {
             if (action == PlatformAction.Copy)
-                host.GetClipboard().SetText(formatSelectionAsString());
+                host.GetClipboard()?.SetText(formatSelectionAsString());
 
             return false;
         }