Merge pull request #11017 from peppy/fix-song-select-temporary-selection-loss

Fix current beatmap temporarily becoming empty during ruleset change

osu.Game.Tests/Visual/SongSelect/TestScenePlaySongSelect.cs

@@ -643,6 +643,55 @@ namespace osu.Game.Tests.Visual.SongSelect
             AddAssert("Selected beatmap correct", () => songSelect.Carousel.SelectedBeatmap == filteredBeatmap);
         }
 
+        [Test]
+        public void TestChangingRulesetOnMultiRulesetBeatmap()
+        {
+            int changeCount = 0;
+
+            AddStep("change convert setting", () => config.Set(OsuSetting.ShowConvertedBeatmaps, false));
+            AddStep("bind beatmap changed", () =>
+            {
+                Beatmap.ValueChanged += onChange;
+                changeCount = 0;
+            });
+
+            changeRuleset(0);
+
+            createSongSelect();
+
+            AddStep("import multi-ruleset map", () =>
+            {
+                var usableRulesets = rulesets.AvailableRulesets.Where(r => r.ID != 2).ToArray();
+                manager.Import(createTestBeatmapSet(usableRulesets)).Wait();
+            });
+
+            int previousSetID = 0;
+
+            AddUntilStep("wait for selection", () => !Beatmap.IsDefault);
+
+            AddStep("record set ID", () => previousSetID = Beatmap.Value.BeatmapSetInfo.ID);
+            AddAssert("selection changed once", () => changeCount == 1);
+
+            AddAssert("Check ruleset is osu!", () => Ruleset.Value.ID == 0);
+
+            changeRuleset(3);
+
+            AddUntilStep("Check ruleset changed to mania", () => Ruleset.Value.ID == 3);
+
+            AddUntilStep("selection changed", () => changeCount > 1);
+
+            AddAssert("Selected beatmap still same set", () => Beatmap.Value.BeatmapSetInfo.ID == previousSetID);
+            AddAssert("Selected beatmap is mania", () => Beatmap.Value.BeatmapInfo.Ruleset.ID == 3);
+
+            AddAssert("selection changed only fired twice", () => changeCount == 2);
+
+            AddStep("unbind beatmap changed", () => Beatmap.ValueChanged -= onChange);
+            AddStep("change convert setting", () => config.Set(OsuSetting.ShowConvertedBeatmaps, true));
+
+            // ReSharper disable once AccessToModifiedClosure
+            void onChange(ValueChangedEvent<WorkingBeatmap> valueChangedEvent) => changeCount++;
+        }
+
         [Test]
         public void TestDifficultyIconSelectingForDifferentRuleset()
         {

osu.Game/Screens/Select/SongSelect.cs

@@ -376,7 +376,7 @@ namespace osu.Game.Screens.Select
             if (selectionChangedDebounce?.Completed == false)
             {
                 selectionChangedDebounce.RunTask();
-                selectionChangedDebounce.Cancel(); // cancel the already scheduled task.
+                selectionChangedDebounce?.Cancel(); // cancel the already scheduled task.
                 selectionChangedDebounce = null;
             }
 
@@ -465,19 +465,30 @@ namespace osu.Game.Screens.Select
 
             void run()
             {
+                // clear pending task immediately to track any potential nested debounce operation.
+                selectionChangedDebounce = null;
+
                 Logger.Log($"updating selection with beatmap:{beatmap?.ID.ToString() ?? "null"} ruleset:{ruleset?.ID.ToString() ?? "null"}");
 
                 if (transferRulesetValue())
                 {
                     Mods.Value = Array.Empty<Mod>();
 
-                    // transferRulesetValue() may trigger a refilter. If the current selection does not match the new ruleset, we want to switch away from it.
+                    // transferRulesetValue() may trigger a re-filter. If the current selection does not match the new ruleset, we want to switch away from it.
                     // The default logic on WorkingBeatmap change is to switch to a matching ruleset (see workingBeatmapChanged()), but we don't want that here.
                     // We perform an early selection attempt and clear out the beatmap selection to avoid a second ruleset change (revert).
                     if (beatmap != null && !Carousel.SelectBeatmap(beatmap, false))
                         beatmap = null;
                 }
 
+                if (selectionChangedDebounce != null)
+                {
+                    // a new nested operation was started; switch to it for further selection.
+                    // this avoids having two separate debounces trigger from the same source.
+                    selectionChangedDebounce.RunTask();
+                    return;
+                }
+
                 // We may be arriving here due to another component changing the bindable Beatmap.
                 // In these cases, the other component has already loaded the beatmap, so we don't need to do so again.
                 if (!EqualityComparer<BeatmapInfo>.Default.Equals(beatmap, Beatmap.Value.BeatmapInfo))