Add failing test case covering online ID reset on save

This test scene passes at e58e1151f3 and
fails at current master, due to an inadvertent regression caused by
e72f103c17.

As it turns out, the online lookup flow that was causing UI thread
freezes when saving beatmaps in the editor, was also responsible for
resetting the online ID of locally-modified beatmaps if online lookup
failed.

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

@@ -0,0 +1,56 @@
+// 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 System.Net;
+using NUnit.Framework;
+using osu.Framework.Extensions;
+using osu.Game.Database;
+using osu.Game.Online.API;
+using osu.Game.Online.API.Requests;
+using osu.Game.Tests.Resources;
+
+namespace osu.Game.Tests.Visual.Editing
+{
+    public partial class TestSceneLocallyModifyingOnlineBeatmaps : EditorSavingTestScene
+    {
+        private DummyAPIAccess dummyAPI => (DummyAPIAccess)API;
+
+        public override void SetUpSteps()
+        {
+            CreateInitialBeatmap = () =>
+            {
+                var importedSet = Game.BeatmapManager.Import(new ImportTask(TestResources.GetTestBeatmapForImport())).GetResultSafely();
+                return Game.BeatmapManager.GetWorkingBeatmap(importedSet!.Value.Beatmaps.First());
+            };
+
+            base.SetUpSteps();
+        }
+
+        [Test]
+        public void TestLocallyModifyingOnlineBeatmap()
+        {
+            AddAssert("editor beatmap has online ID", () => EditorBeatmap.BeatmapInfo.OnlineID, () => Is.GreaterThan(0));
+
+            AddStep("delete first hitobject", () => EditorBeatmap.RemoveAt(0));
+
+            AddStep("mock online lookup failure", () =>
+            {
+                dummyAPI.HandleRequest = req =>
+                {
+                    if (req is GetBeatmapRequest)
+                    {
+                        req.TriggerFailure(new APIException("Beatmap not found", new WebException("NotFound")));
+                        return true;
+                    }
+
+                    return false;
+                };
+            });
+            SaveEditor();
+
+            ReloadEditorToSameBeatmap();
+            AddAssert("editor beatmap online ID reset", () => EditorBeatmap.BeatmapInfo.OnlineID, () => Is.EqualTo(-1));
+        }
+    }
+}

osu.Game/Tests/Visual/EditorSavingTestScene.cs

@@ -3,9 +3,12 @@
 
 #nullable disable
 
+using System;
 using System.Linq;
+using JetBrains.Annotations;
 using osu.Framework.Input;
 using osu.Framework.Testing;
+using osu.Game.Beatmaps;
 using osu.Game.Rulesets.Edit;
 using osu.Game.Screens.Edit;
 using osu.Game.Screens.Edit.Setup;
@@ -24,18 +27,27 @@ namespace osu.Game.Tests.Visual
 
         protected EditorBeatmap EditorBeatmap => (EditorBeatmap)Editor.Dependencies.Get(typeof(EditorBeatmap));
 
+        [CanBeNull]
+        protected Func<WorkingBeatmap> CreateInitialBeatmap { get; set; }
+
         [SetUpSteps]
         public override void SetUpSteps()
         {
             base.SetUpSteps();
 
-            AddStep("set default beatmap", () => Game.Beatmap.SetDefault());
+            if (CreateInitialBeatmap == null)
+                AddStep("set default beatmap", () => Game.Beatmap.SetDefault());
+            else
+            {
+                AddStep("set test beatmap", () => Game.Beatmap.Value = CreateInitialBeatmap?.Invoke());
+            }
 
             PushAndConfirm(() => new EditorLoader());
 
             AddUntilStep("wait for editor load", () => Editor?.IsLoaded == true);
 
-            AddUntilStep("wait for metadata screen load", () => Editor.ChildrenOfType<MetadataSection>().FirstOrDefault()?.IsLoaded == true);
+            if (CreateInitialBeatmap == null)
+                AddUntilStep("wait for metadata screen load", () => Editor.ChildrenOfType<MetadataSection>().FirstOrDefault()?.IsLoaded == true);
 
             // We intentionally switch away from the metadata screen, else there is a feedback loop with the textbox handling which causes metadata changes below to get overwritten.
 
@@ -50,6 +62,14 @@ namespace osu.Game.Tests.Visual
 
         protected void ReloadEditorToSameBeatmap()
         {
+            Guid beatmapSetGuid = Guid.Empty;
+            Guid beatmapGuid = Guid.Empty;
+
+            AddStep("Store beatmap GUIDs", () =>
+            {
+                beatmapSetGuid = EditorBeatmap.BeatmapInfo.BeatmapSet!.ID;
+                beatmapGuid = EditorBeatmap.BeatmapInfo.ID;
+            });
             AddStep("Exit", () => InputManager.Key(Key.Escape));
 
             AddUntilStep("Wait for main menu", () => Game.ScreenStack.CurrentScreen is MainMenu);
@@ -59,7 +79,8 @@ namespace osu.Game.Tests.Visual
             PushAndConfirm(() => songSelect = new PlaySongSelect());
             AddUntilStep("wait for carousel load", () => songSelect.BeatmapSetsLoaded);
 
-            AddUntilStep("Wait for beatmap selected", () => !Game.Beatmap.IsDefault);
+            AddStep("Present same beatmap", () => Game.PresentBeatmap(Game.BeatmapManager.QueryBeatmapSet(set => set.ID == beatmapSetGuid)!.Value, beatmap => beatmap.ID == beatmapGuid));
+            AddUntilStep("Wait for beatmap selected", () => Game.Beatmap.Value.BeatmapInfo.ID == beatmapGuid);
             AddStep("Open options", () => InputManager.Key(Key.F3));
             AddStep("Enter editor", () => InputManager.Key(Key.Number5));