Fix various other inspections

osu.Game.Rulesets.Osu.Tests/Editor/TestSceneObjectMerging.cs

@@ -34,7 +34,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Editor
             });
 
             moveMouseToHitObject(1);
-            AddAssert("merge option available", () => selectionHandler.ContextMenuItems.Any(o => o.Text.Value == "Merge selection"));
+            AddAssert("merge option available", () => selectionHandler.ContextMenuItems?.Any(o => o.Text.Value == "Merge selection") == true);
 
             mergeSelection();
 
@@ -198,7 +198,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Editor
             });
 
             moveMouseToHitObject(1);
-            AddAssert("merge option not available", () => selectionHandler.ContextMenuItems.Length > 0 && selectionHandler.ContextMenuItems.All(o => o.Text.Value != "Merge selection"));
+            AddAssert("merge option not available", () => selectionHandler.ContextMenuItems?.Length > 0 && selectionHandler.ContextMenuItems.All(o => o.Text.Value != "Merge selection"));
             mergeSelection();
             AddAssert("circles not merged", () => circle1 is not null && circle2 is not null
                                                                       && EditorBeatmap.HitObjects.Contains(circle1) && EditorBeatmap.HitObjects.Contains(circle2));
@@ -222,7 +222,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Editor
             });
 
             moveMouseToHitObject(1);
-            AddAssert("merge option available", () => selectionHandler.ContextMenuItems.Any(o => o.Text.Value == "Merge selection"));
+            AddAssert("merge option available", () => selectionHandler.ContextMenuItems?.Any(o => o.Text.Value == "Merge selection") == true);
 
             mergeSelection();
 

osu.Game.Rulesets.Osu.Tests/Editor/TestSceneSliderSplitting.cs

@@ -241,7 +241,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Editor
             {
                 if (visualiser is null) return;
 
-                MenuItem? item = visualiser.ContextMenuItems.FirstOrDefault(menuItem => menuItem.Text.Value == contextMenuText);
+                MenuItem? item = visualiser.ContextMenuItems?.FirstOrDefault(menuItem => menuItem.Text.Value == contextMenuText);
 
                 item?.Action.Value?.Invoke();
             });

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

@@ -182,7 +182,7 @@ namespace osu.Game.Tests.Visual.Editing
             if (sameRuleset)
             {
                 AddUntilStep("wait for dialog", () => DialogOverlay.CurrentDialog is CreateNewDifficultyDialog);
-                AddStep("confirm creation with no objects", () => DialogOverlay.CurrentDialog.PerformOkAction());
+                AddStep("confirm creation with no objects", () => DialogOverlay.CurrentDialog!.PerformOkAction());
             }
 
             AddUntilStep("wait for created", () =>
@@ -269,7 +269,7 @@ namespace osu.Game.Tests.Visual.Editing
             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());
+            AddStep("confirm creation as a copy", () => DialogOverlay.CurrentDialog!.Buttons.ElementAt(1).TriggerClick());
 
             AddUntilStep("wait for created", () =>
             {
@@ -342,7 +342,7 @@ namespace osu.Game.Tests.Visual.Editing
             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());
+            AddStep("confirm creation as a copy", () => DialogOverlay.CurrentDialog!.Buttons.ElementAt(1).TriggerClick());
 
             AddUntilStep("wait for created", () =>
             {
@@ -380,7 +380,7 @@ namespace osu.Game.Tests.Visual.Editing
 
             AddStep("try to create new difficulty", () => Editor.CreateNewDifficulty(new OsuRuleset().RulesetInfo));
             AddUntilStep("wait for dialog", () => DialogOverlay.CurrentDialog is CreateNewDifficultyDialog);
-            AddStep("confirm creation with no objects", () => DialogOverlay.CurrentDialog.PerformOkAction());
+            AddStep("confirm creation with no objects", () => DialogOverlay.CurrentDialog!.PerformOkAction());
 
             AddUntilStep("wait for created", () =>
             {
@@ -415,7 +415,7 @@ namespace osu.Game.Tests.Visual.Editing
             if (sameRuleset)
             {
                 AddUntilStep("wait for dialog", () => DialogOverlay.CurrentDialog is CreateNewDifficultyDialog);
-                AddStep("confirm creation with no objects", () => DialogOverlay.CurrentDialog.PerformOkAction());
+                AddStep("confirm creation with no objects", () => DialogOverlay.CurrentDialog!.PerformOkAction());
             }
 
             AddUntilStep("wait for created", () =>
@@ -476,7 +476,7 @@ namespace osu.Game.Tests.Visual.Editing
 
             AddStep("exit", () => Editor.Exit());
             AddUntilStep("wait for dialog", () => DialogOverlay.CurrentDialog is PromptForSaveDialog);
-            AddStep("attempt to save", () => DialogOverlay.CurrentDialog.PerformOkAction());
+            AddStep("attempt to save", () => DialogOverlay.CurrentDialog!.PerformOkAction());
             AddAssert("editor is still current", () => Editor.IsCurrentScreen());
         }
 

osu.Game.Tournament/Components/DateTextBox.cs

@@ -15,7 +15,7 @@ namespace osu.Game.Tournament.Components
         public new Bindable<DateTimeOffset>? Current
         {
             get => current;
-            set => current.Current = value;
+            set => current.Current = value!;
         }
 
         public DateTextBox()

osu.Game/Beatmaps/DummyWorkingBeatmap.cs

@@ -70,9 +70,9 @@ namespace osu.Game.Beatmaps
                 throw new NotImplementedException();
             }
 
-            public override IBeatmapConverter CreateBeatmapConverter(IBeatmap beatmap) => new DummyBeatmapConverter { Beatmap = beatmap };
+            public override IBeatmapConverter CreateBeatmapConverter(IBeatmap beatmap) => new DummyBeatmapConverter(beatmap);
 
-            public override DifficultyCalculator CreateDifficultyCalculator(IWorkingBeatmap beatmap) => null;
+            public override DifficultyCalculator CreateDifficultyCalculator(IWorkingBeatmap beatmap) => throw new NotImplementedException();
 
             public override string Description => "dummy";
 
@@ -80,9 +80,15 @@ namespace osu.Game.Beatmaps
 
             private class DummyBeatmapConverter : IBeatmapConverter
             {
-                public event Action<HitObject, IEnumerable<HitObject>> ObjectConverted;
+                public IBeatmap Beatmap { get; }
 
-                public IBeatmap Beatmap { get; set; }
+                public DummyBeatmapConverter(IBeatmap beatmap)
+                {
+                    Beatmap = beatmap;
+                }
+
+                [CanBeNull]
+                public event Action<HitObject, IEnumerable<HitObject>> ObjectConverted;
 
                 public bool CanConvert() => true;
 

osu.Game/Beatmaps/WorkingBeatmapCache.cs

@@ -86,7 +86,7 @@ namespace osu.Game.Beatmaps
 
         public event Action<WorkingBeatmap> OnInvalidated;
 
-        public virtual WorkingBeatmap GetWorkingBeatmap(BeatmapInfo beatmapInfo)
+        public virtual WorkingBeatmap GetWorkingBeatmap([CanBeNull] BeatmapInfo beatmapInfo)
         {
             if (beatmapInfo?.BeatmapSet == null)
                 return DefaultBeatmap;

osu.Game/Graphics/Backgrounds/SkinBackground.cs

@@ -22,7 +22,7 @@ namespace osu.Game.Graphics.Backgrounds
             Sprite.Texture = skin.GetTexture("menu-background") ?? Sprite.Texture;
         }
 
-        public override bool Equals(Background other)
+        public override bool Equals(Background? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;

osu.Game/Graphics/Containers/SectionsContainer.cs

@@ -119,11 +119,11 @@ namespace osu.Game.Graphics.Containers
                 headerBackgroundContainer.Clear();
                 headerBackground = value;
 
-                if (value == null) return;
+                if (headerBackground != null)
-
+                {
-                headerBackgroundContainer.Add(headerBackground);
+                    headerBackgroundContainer.Add(headerBackground);
-
+                    lastKnownScroll = null;
-                lastKnownScroll = null;
+                }
             }
         }
 

osu.Game/Graphics/UserInterface/OsuSliderBar.cs

@@ -62,7 +62,7 @@ namespace osu.Game.Graphics.UserInterface
             if (!PlaySamplesOnAdjust)
                 return;
 
-            if (Clock == null || Clock.CurrentTime - lastSampleTime <= 30)
+            if (Clock.CurrentTime - lastSampleTime <= 30)
                 return;
 
             if (value.Equals(lastSampleValue))

osu.Game/IO/FileInfo.cs

@@ -13,7 +13,7 @@ namespace osu.Game.IO
 
         public bool IsManaged => ID > 0;
 
-        public string Hash { get; set; }
+        public string Hash { get; set; } = string.Empty;
 
         public int ReferenceCount { get; set; }
     }

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

@@ -29,7 +29,7 @@ namespace osu.Game.Online.API.Requests.Responses
         public DateTimeOffset JoinDate;
 
         [JsonProperty(@"username")]
-        public string Username { get; set; }
+        public string Username { get; set; } = string.Empty;
 
         [JsonProperty(@"previous_usernames")]
         public string[] PreviousUsernames;

osu.Game/Online/Placeholders/MessagePlaceholder.cs

@@ -22,6 +22,6 @@ namespace osu.Game.Online.Placeholders
             AddText(this.message = message);
         }
 
-        public override bool Equals(Placeholder other) => (other as MessagePlaceholder)?.message == message;
+        public override bool Equals(Placeholder? other) => (other as MessagePlaceholder)?.message == message;
     }
 }

osu.Game/Overlays/FullscreenOverlay.cs

@@ -17,7 +17,7 @@ namespace osu.Game.Overlays
     public abstract partial class FullscreenOverlay<T> : WaveOverlayContainer, INamedOverlayComponent
         where T : OverlayHeader
     {
-        public virtual string IconTexture => Header.Title.IconTexture ?? string.Empty;
+        public virtual string IconTexture => Header.Title.IconTexture;
         public virtual LocalisableString Title => Header.Title.Title;
         public virtual LocalisableString Description => Header.Title.Description;
 

osu.Game/Rulesets/Objects/Legacy/ConvertSlider.cs

@@ -23,11 +23,12 @@ namespace osu.Game.Rulesets.Objects.Legacy
         /// <summary>
         /// <see cref="ConvertSlider"/>s don't need a curve since they're converted to ruleset-specific hitobjects.
         /// </summary>
-        public SliderPath Path { get; set; }
+        public SliderPath Path { get; set; } = null!;
 
         public double Distance => Path.Distance;
 
-        public IList<IList<HitSampleInfo>> NodeSamples { get; set; }
+        public IList<IList<HitSampleInfo>> NodeSamples { get; set; } = null!;
+
         public int RepeatCount { get; set; }
 
         [JsonIgnore]

osu.Game/Rulesets/UI/DrawableRulesetDependencies.cs

@@ -186,7 +186,7 @@ namespace osu.Game.Rulesets.UI
                 this.fallback = fallback;
             }
 
-            public override Texture Get(string name, WrapMode wrapModeS, WrapMode wrapModeT)
+            public override Texture? Get(string name, WrapMode wrapModeS, WrapMode wrapModeT)
                 => primary.Get(name, wrapModeS, wrapModeT) ?? fallback.Get(name, wrapModeS, wrapModeT);
 
             protected override void Dispose(bool disposing)

osu.Game/Screens/Backgrounds/BackgroundScreenCustom.cs

@@ -15,7 +15,7 @@ namespace osu.Game.Screens.Backgrounds
             AddInternal(new Background(textureName));
         }
 
-        public override bool Equals(BackgroundScreen other)
+        public override bool Equals(BackgroundScreen? other)
         {
             if (other is BackgroundScreenCustom backgroundScreenCustom)
                 return base.Equals(other) && textureName == backgroundScreenCustom.textureName;

osu.Game/Screens/OsuScreen.cs

@@ -89,9 +89,9 @@ namespace osu.Game.Screens
 
         public virtual bool? AllowGlobalTrackControl => null;
 
-        public Bindable<WorkingBeatmap> Beatmap { get; private set; }
+        public Bindable<WorkingBeatmap> Beatmap { get; private set; } = null!;
 
-        public Bindable<RulesetInfo> Ruleset { get; private set; }
+        public Bindable<RulesetInfo> Ruleset { get; private set; } = null!;
 
         public Bindable<IReadOnlyList<Mod>> Mods { get; private set; }
 

osu.Game/Screens/Play/SkipOverlay.cs

@@ -4,6 +4,7 @@
 #nullable disable
 
 using System;
+using JetBrains.Annotations;
 using osu.Framework;
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
@@ -211,6 +212,7 @@ namespace osu.Game.Screens.Play
 
         public partial class FadeContainer : Container, IStateful<Visibility>
         {
+            [CanBeNull]
             public event Action<Visibility> StateChanged;
 
             private Visibility state;

osu.Game/Screens/Select/SongSelect.cs

@@ -647,7 +647,7 @@ namespace osu.Game.Screens.Select
 
             beginLooping();
 
-            if (Beatmap != null && !Beatmap.Value.BeatmapSetInfo.DeletePending)
+            if (!Beatmap.Value.BeatmapSetInfo.DeletePending)
             {
                 updateCarouselSelection();