Avoid zero-length array allocations (#19300)

* Avoid zero-length array allocations * Enforce CA1825 solution-wide --------- Co-authored-by: Jeremy Powell <jeremy@visionaid.com>
dotnet · Jan 16, 2024 · 5727faa · 5727faa
1 parent 3890e04
commit 5727faa
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Showing 44 changed files with 68 additions and 63 deletions.
diff --git a/.editorconfig b/.editorconfig
@@ -29,6 +29,7 @@ dotnet_diagnostic.CA1307.severity = error
 dotnet_diagnostic.CA1309.severity = error
 dotnet_diagnostic.CA1311.severity = error
 dotnet_diagnostic.CA1815.severity = error
+dotnet_diagnostic.CA1825.severity = error
 
 # nullability checks
 

diff --git a/src/Compatibility/ControlGallery/src/Issues.Shared/Issue4597.cs b/src/Compatibility/ControlGallery/src/Issues.Shared/Issue4597.cs
@@ -290,7 +290,7 @@ Xamarin.UITest.Queries.AppResult TestForImageVisible()
 				if (result[0].Rect.Height > 1)
 					return result;
 
-				return new Xamarin.UITest.Queries.AppResult[0];
+				return Array.Empty<Xamarin.UITest.Queries.AppResult>();
 			}, 10, 4000);
 
 			Assert.AreEqual(1, images.Length);

diff --git a/src/Compatibility/Core/src/Android/CollectionView/SelectableItemsViewAdapter.cs b/src/Compatibility/Core/src/Android/CollectionView/SelectableItemsViewAdapter.cs
@@ -81,13 +81,13 @@ int[] GetSelectedPositions()
 			switch (ItemsView.SelectionMode)
 			{
 				case SelectionMode.None:
-					return new int[0];
+					return Array.Empty<int>();
 
 				case SelectionMode.Single:
 					var selectedItem = ItemsView.SelectedItem;
 					if (selectedItem == null)
 					{
-						return new int[0];
+						return Array.Empty<int>();
 					}
 
 					return new int[1] { GetPositionForItem(selectedItem) };
@@ -104,7 +104,7 @@ int[] GetSelectedPositions()
 					return result;
 			}
 
-			return new int[0];
+			return Array.Empty<int>();
 		}
 
 		bool PositionIsSelected(int position)

diff --git a/src/Compatibility/Core/src/Android/Renderers/EditorRenderer.cs b/src/Compatibility/Core/src/Android/Renderers/EditorRenderer.cs
@@ -293,7 +293,7 @@ void OnKeyboardBackPressed(object sender, EventArgs eventArgs)
 		[PortHandler]
 		void UpdateMaxLength()
 		{
-			var currentFilters = new List<IInputFilter>(EditText?.GetFilters() ?? new IInputFilter[0]);
+			var currentFilters = new List<IInputFilter>(EditText?.GetFilters() ?? Array.Empty<IInputFilter>());
 
 			for (var i = 0; i < currentFilters.Count; i++)
 			{

diff --git a/src/Compatibility/Core/src/Android/Renderers/EntryRenderer.cs b/src/Compatibility/Core/src/Android/Renderers/EntryRenderer.cs
@@ -379,7 +379,7 @@ void OnKeyboardBackPressed(object sender, EventArgs eventArgs)
 		[PortHandler]
 		void UpdateMaxLength()
 		{
-			var currentFilters = new List<IInputFilter>(EditText?.GetFilters() ?? new IInputFilter[0]);
+			var currentFilters = new List<IInputFilter>(EditText?.GetFilters() ?? Array.Empty<IInputFilter>());
 
 			for (var i = 0; i < currentFilters.Count; i++)
 			{

diff --git a/src/Compatibility/Core/src/Android/Renderers/SearchBarRenderer.cs b/src/Compatibility/Core/src/Android/Renderers/SearchBarRenderer.cs
@@ -290,7 +290,7 @@ void UpdateMaxLength()
 		{
 			_editText = _editText ?? Control.GetChildrenOfType<AppCompatAutoCompleteTextView>().FirstOrDefault();
 
-			var currentFilters = new List<IInputFilter>(_editText?.GetFilters() ?? new IInputFilter[0]);
+			var currentFilters = new List<IInputFilter>(_editText?.GetFilters() ?? Array.Empty<IInputFilter>());
 
 			for (var i = 0; i < currentFilters.Count; i++)
 			{

diff --git a/src/Compatibility/Core/src/Tizen/Forms.cs b/src/Compatibility/Core/src/Tizen/Forms.cs
@@ -103,7 +103,7 @@ public static class Forms
 
 		public static Size PhysicalScreenSize => DeviceDisplay.MainDisplayInfo.GetScaledScreenSize();
 
-		public static IReadOnlyList<string> Flags => s_flags ?? (s_flags = new string[0]);
+		public static IReadOnlyList<string> Flags => s_flags ?? (s_flags = Array.Empty<string>());
 
 		public static IMauiContext MauiContext { get; internal set; }
 

diff --git a/src/Compatibility/Core/src/iOS/DragAndDropDelegate.cs b/src/Compatibility/Core/src/iOS/DragAndDropDelegate.cs
@@ -34,7 +34,7 @@ public UIDragItem[] GetItemsForBeginningSession(UIDragInteraction interaction, I
 			if (interaction.View is IVisualElementRenderer renderer && renderer.Element is View view)
 				return HandleDragStarting(view, renderer);
 
-			return new UIDragItem[0];
+			return Array.Empty<UIDragItem>();
 		}
 
 		[Export("dropInteraction:canHandleSession:")]
@@ -193,7 +193,7 @@ public UIDragItem[] HandleDragStarting(View element, IVisualElementRenderer rend
 			},
 			element);
 
-			return returnValue ?? new UIDragItem[0];
+			return returnValue ?? Array.Empty<UIDragItem>();
 		}
 
 		void HandleDropCompleted(View element)

diff --git a/src/Compatibility/Core/src/iOS/Extensions/DoubleCollectionExtensions.cs b/src/Compatibility/Core/src/iOS/Extensions/DoubleCollectionExtensions.cs
@@ -12,7 +12,7 @@ public static class DoubleCollectionExtensions
 		public static nfloat[] ToArray(this DoubleCollection doubleCollection)
 		{
 			if (doubleCollection == null || doubleCollection.Count == 0)
-				return new nfloat[0];
+				return Array.Empty<nfloat>();
 			else
 			{
 

diff --git a/src/Compatibility/Core/src/iOS/Extensions/PointCollectionExtensions.cs b/src/Compatibility/Core/src/iOS/Extensions/PointCollectionExtensions.cs
@@ -14,7 +14,7 @@ public static CGPoint[] ToCGPoints(this PointCollection pointCollection)
 		{
 			if (pointCollection == null || pointCollection.Count == 0)
 			{
-				return new CGPoint[0];
+				return System.Array.Empty<CGPoint>();
 			}
 
 			CGPoint[] points = new CGPoint[pointCollection.Count];

diff --git a/src/Compatibility/Core/src/iOS/Renderers/NavigationRenderer.cs b/src/Compatibility/Core/src/iOS/Renderers/NavigationRenderer.cs
@@ -1422,8 +1422,8 @@ void UpdateToolbarItems()
 
 				if (primaries != null)
 					primaries.Reverse();
-				NavigationItem.SetRightBarButtonItems(primaries == null ? new UIBarButtonItem[0] : primaries.ToArray(), false);
-				ToolbarItems = secondaries == null ? new UIBarButtonItem[0] : secondaries.ToArray();
+				NavigationItem.SetRightBarButtonItems(primaries == null ? Array.Empty<UIBarButtonItem>() : primaries.ToArray(), false);
+				ToolbarItems = secondaries == null ? Array.Empty<UIBarButtonItem>() : secondaries.ToArray();
 
 				NavigationRenderer n;
 				if (_navigation.TryGetTarget(out n))

diff --git a/src/Compatibility/Core/src/iOS/Renderers/WkWebViewRenderer.cs b/src/Compatibility/Core/src/iOS/Renderers/WkWebViewRenderer.cs
@@ -358,7 +358,7 @@ async Task<List<NSHttpCookie>> GetCookiesFromNativeStore(string url)
 				}
 			}
 
-			_initialCookiesLoaded = _initialCookiesLoaded ?? new NSHttpCookie[0];
+			_initialCookiesLoaded = _initialCookiesLoaded ?? Array.Empty<NSHttpCookie>();
 
 			List<NSHttpCookie> existingCookies = new List<NSHttpCookie>();
 			string domain = CreateUriForCookies(url).Host;

diff --git a/src/Compatibility/Core/src/iOS/Shapes/ShapeRenderer.cs b/src/Compatibility/Core/src/iOS/Shapes/ShapeRenderer.cs
@@ -124,7 +124,7 @@ void UpdateStrokeThickness()
 		void UpdateStrokeDashArray()
 		{
 			if (Element.StrokeDashArray == null || Element.StrokeDashArray.Count == 0)
-				Control.ShapeLayer.UpdateStrokeDash(new nfloat[0]);
+				Control.ShapeLayer.UpdateStrokeDash(Array.Empty<nfloat>());
 			else
 			{
 				nfloat[] dashArray;

diff --git a/src/Controls/Foldable/src/DualScreenInfo.cs b/src/Controls/Foldable/src/DualScreenInfo.cs
@@ -69,7 +69,7 @@ public DualScreenInfo(VisualElement element) : this(element, null)
 
 		internal DualScreenInfo(VisualElement element, IFoldableService dualScreenService)
 		{
-			_spanningBounds = new Rect[0];
+			_spanningBounds = Array.Empty<Rect>();
 			Element = element;
 			_dualScreenService = dualScreenService;
 
@@ -179,10 +179,10 @@ Rect[] GetSpanningBounds()
 			var hinge = guide.Hinge;
 
 			if (hinge == Rect.Zero)
-				return new Rect[0];
+				return Array.Empty<Rect>();
 
 			if (guide.Pane2 == Rect.Zero)
-				return new Rect[0];
+				return Array.Empty<Rect>();
 
 			//TODO: I think this should this be checking SpanMode==Wide
 			if (IsLandscape)

diff --git a/...rols/samples/Controls.Sample/Pages/Controls/CollectionViewGalleries/CollectionModifier.cs b/...rols/samples/Controls.Sample/Pages/Controls/CollectionViewGalleries/CollectionModifier.cs
@@ -50,7 +50,7 @@ protected virtual bool ParseIndexes(out int[] indexes)
 		{
 			if (!int.TryParse(Entry.Text, out int index))
 			{
-				indexes = new int[0];
+				indexes = Array.Empty<int>();
 				return false;
 			}
 

diff --git a/src/Controls/src/Core/Compatibility/Handlers/NavigationPage/iOS/NavigationRenderer.cs b/src/Controls/src/Core/Compatibility/Handlers/NavigationPage/iOS/NavigationRenderer.cs
@@ -1531,8 +1531,8 @@ void UpdateToolbarItems()
 
 				if (primaries != null)
 					primaries.Reverse();
-				NavigationItem.SetRightBarButtonItems(primaries == null ? new UIBarButtonItem[0] : primaries.ToArray(), false);
-				ToolbarItems = secondaries == null ? new UIBarButtonItem[0] : secondaries.ToArray();
+				NavigationItem.SetRightBarButtonItems(primaries == null ? Array.Empty<UIBarButtonItem>() : primaries.ToArray(), false);
+				ToolbarItems = secondaries == null ? Array.Empty<UIBarButtonItem>() : secondaries.ToArray();
 
 				NavigationRenderer n;
 				if (_navigation.TryGetTarget(out n))

diff --git a/src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemRenderer.cs b/src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellItemRenderer.cs
@@ -14,6 +14,8 @@ namespace Microsoft.Maui.Controls.Platform.Compatibility
 {
 	public class ShellItemRenderer : UITabBarController, IShellItemRenderer, IAppearanceObserver, IUINavigationControllerDelegate, IDisconnectable
 	{
+		readonly static UITableViewCell[] EmptyUITableViewCellArray = Array.Empty<UITableViewCell>();
+
 		#region IShellItemRenderer
 
 		public ShellItem ShellItem
@@ -346,7 +348,7 @@ UITableViewCell[] GetMoreNavigationCells()
 				if (MoreNavigationController.TopViewController.View is UITableView uITableView)
 					return uITableView.VisibleCells;
 
-				return new UITableViewCell[0];
+				return EmptyUITableViewCellArray;
 			}
 		}
 

diff --git a/src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellPageRendererTracker.cs b/src/Controls/src/Core/Compatibility/Handlers/Shell/iOS/ShellPageRendererTracker.cs
@@ -302,7 +302,7 @@ protected virtual void UpdateToolbarItems()
 					primaries.Reverse();
 			}
 
-			NavigationItem.SetRightBarButtonItems(primaries == null ? new UIBarButtonItem[0] : primaries.ToArray(), false);
+			NavigationItem.SetRightBarButtonItems(primaries == null ? Array.Empty<UIBarButtonItem>() : primaries.ToArray(), false);
 
 			UpdateLeftToolbarItems();
 		}

diff --git a/src/Controls/src/Core/Handlers/Items/Android/Adapters/SelectableItemsViewAdapter.cs b/src/Controls/src/Core/Handlers/Items/Android/Adapters/SelectableItemsViewAdapter.cs
@@ -81,13 +81,13 @@ int[] GetSelectedPositions()
 			switch (ItemsView.SelectionMode)
 			{
 				case SelectionMode.None:
-					return new int[0];
+					return Array.Empty<int>();
 
 				case SelectionMode.Single:
 					var selectedItem = ItemsView.SelectedItem;
 					if (selectedItem == null)
 					{
-						return new int[0];
+						return Array.Empty<int>();
 					}
 
 					return new int[1] { GetPositionForItem(selectedItem) };
@@ -104,7 +104,7 @@ int[] GetSelectedPositions()
 					return result;
 			}
 
-			return new int[0];
+			return Array.Empty<int>();
 		}
 
 		bool PositionIsSelected(int position)

diff --git a/src/Controls/src/Core/LegacyLayouts/ConstraintExpression.cs b/src/Controls/src/Core/LegacyLayouts/ConstraintExpression.cs
@@ -40,7 +40,7 @@ public Constraint ProvideValue(IServiceProvider serviceProvider)
 					if (string.IsNullOrEmpty(Property))
 						return null;
 					minfo = typeof(View).GetProperties().First(pi => pi.Name == Property && pi.CanRead && pi.GetMethod.IsPublic).GetMethod;
-					return Constraint.RelativeToParent(p => (double)minfo.Invoke(p, new object[] { }) * Factor + Constant);
+					return Constraint.RelativeToParent(p => (double)minfo.Invoke(p, Array.Empty<object>()) * Factor + Constant);
 				case ConstraintType.Constant:
 					return Constraint.Constant(Constant);
 				case ConstraintType.RelativeToView:
@@ -62,7 +62,7 @@ public Constraint ProvideValue(IServiceProvider serviceProvider)
 						view = ((INameScope)valueProvider.TargetObject).FindByName<View>(ElementName);
 					}
 					return Constraint.RelativeToView(view, delegate (RelativeLayout p, View v)
-					{ return (double)minfo.Invoke(v, new object[] { }) * Factor + Constant; });
+					{ return (double)minfo.Invoke(v, Array.Empty<object>()) * Factor + Constant; });
 			}
 		}
 	}

diff --git a/src/Controls/src/Core/Menu/MenuItemTracker.cs b/src/Controls/src/Core/Menu/MenuItemTracker.cs
@@ -52,7 +52,7 @@ public IList<TMenuItem> ToolbarItems
 			get
 			{
 				if (Target == null)
-					return new TMenuItem[0];
+					return Array.Empty<TMenuItem>();
 
 				// I realize this is sorting on every single get but we don't have 
 				// a mechanism in place currently to invalidate a stored version of this

diff --git a/src/Controls/src/Core/Platform/iOS/DragAndDropDelegate.cs b/src/Controls/src/Core/Platform/iOS/DragAndDropDelegate.cs
@@ -231,7 +231,7 @@ public UIDragItem[] HandleDragStarting(View element, IPlatformViewHandler handle
 			},
 			element);
 
-			return returnValue ?? new UIDragItem[0];
+			return returnValue ?? Array.Empty<UIDragItem>();
 		}
 
 		void SetLocalObject(UIDragItem dragItem, IPlatformViewHandler handler, DataPackage data)

diff --git a/src/Controls/src/Core/Platform/iOS/Extensions/BrushExtensions.cs b/src/Controls/src/Core/Platform/iOS/Extensions/BrushExtensions.cs
@@ -1,4 +1,5 @@
 #nullable disable
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using CoreAnimation;
@@ -222,7 +223,7 @@ static CGPoint GetRadialGradientBrushEndPoint(Point startPoint, double radius)
 		static NSNumber[] GetCAGradientLayerLocations(List<GradientStop> gradientStops)
 		{
 			if (gradientStops == null || gradientStops.Count == 0)
-				return new NSNumber[0];
+				return Array.Empty<NSNumber>();
 
 			if (gradientStops.Count > 1 && gradientStops.Any(gt => gt.Offset != 0))
 				return gradientStops.Select(x => new NSNumber(x.Offset)).ToArray();
@@ -254,7 +255,7 @@ static NSNumber[] GetCAGradientLayerLocations(List<GradientStop> gradientStops)
 		static CGColor[] GetCAGradientLayerColors(List<GradientStop> gradientStops)
 		{
 			if (gradientStops == null || gradientStops.Count == 0)
-				return new CGColor[0];
+				return Array.Empty<CGColor>();
 
 			CGColor[] colors = new CGColor[gradientStops.Count];
 

diff --git a/src/Controls/src/Core/PlatformBindingHelpers.cs b/src/Controls/src/Core/PlatformBindingHelpers.cs
@@ -90,7 +90,7 @@ static void SetValueFromNative<TPlatformView>(TPlatformView target, string targe
 			BindableObjectProxy<TPlatformView> proxy;
 			if (!BindableObjectProxy<TPlatformView>.BindableObjectProxies.TryGetValue(target, out proxy))
 				return;
-			SetValueFromRenderer(proxy, bindableProperty, target.GetType().GetProperty(targetProperty)?.GetMethod.Invoke(target, new object[] { }));
+			SetValueFromRenderer(proxy, bindableProperty, target.GetType().GetProperty(targetProperty)?.GetMethod.Invoke(target, Array.Empty<object>()));
 		}
 
 		static void SetValueFromRenderer(BindableObject bindable, BindableProperty property, object value)

diff --git a/src/Controls/src/Core/TemplatedItemsList.cs b/src/Controls/src/Core/TemplatedItemsList.cs
@@ -69,7 +69,7 @@ internal TemplatedItemsList(TView itemsView, BindableProperty itemSourceProperty
 			if (source != null)
 				ListProxy = new ListProxy(source, dispatcher: _itemsView.Dispatcher);
 			else
-				ListProxy = new ListProxy(new object[0], dispatcher: _itemsView.Dispatcher);
+				ListProxy = new ListProxy(Array.Empty<object>(), dispatcher: _itemsView.Dispatcher);
 		}
 
 		internal TemplatedItemsList(TemplatedItemsList<TView, TItem> parent, IEnumerable itemSource, TView itemsView, BindableProperty itemTemplateProperty, int windowSize = int.MaxValue)
@@ -91,7 +91,7 @@ internal TemplatedItemsList(TemplatedItemsList<TView, TItem> parent, IEnumerable
 				ListProxy.CollectionChanged += OnProxyCollectionChanged;
 			}
 			else
-				ListProxy = new ListProxy(new object[0], dispatcher: _itemsView.Dispatcher);
+				ListProxy = new ListProxy(Array.Empty<object>(), dispatcher: _itemsView.Dispatcher);
 		}
 
 		event PropertyChangedEventHandler ITemplatedItemsList<TItem>.PropertyChanged
@@ -944,7 +944,7 @@ void OnItemsSourceChanged(bool fromGrouping = false)
 
 			IEnumerable itemSource = GetItemsViewSource();
 			if (itemSource == null)
-				ListProxy = new ListProxy(new object[0], dispatcher: _itemsView.Dispatcher);
+				ListProxy = new ListProxy(Array.Empty<object>(), dispatcher: _itemsView.Dispatcher);
 			else
 				ListProxy = new ListProxy(itemSource, dispatcher: _itemsView.Dispatcher);
 

diff --git a/src/Controls/src/Xaml/ApplyPropertiesVisitor.cs b/src/Controls/src/Xaml/ApplyPropertiesVisitor.cs
@@ -727,7 +727,7 @@ static bool TryGetProperty(object element, string localName, out object value, I
 			if (!IsVisibleFrom(getter, rootElement))
 				return false;
 
-			value = getter.Invoke(element, new object[] { });
+			value = getter.Invoke(element, Array.Empty<object>());
 			return true;
 		}
 

diff --git a/src/Controls/src/Xaml/CreateValuesVisitor.cs b/src/Controls/src/Xaml/CreateValuesVisitor.cs
@@ -233,7 +233,7 @@ public object CreateFromFactory(Type nodeType, IElementNode node)
 			}
 
 			var factoryMethod = ((string)((ValueNode)node.Properties[XmlName.xFactoryMethod]).Value);
-			Type[] types = arguments == null ? new Type[0] : arguments.Select(a => a.GetType()).ToArray();
+			Type[] types = arguments == null ? Array.Empty<Type>() : arguments.Select(a => a.GetType()).ToArray();
 
 			bool isMatch(MethodInfo m)
 			{

diff --git a/src/Controls/src/Xaml/MarkupExtensions/StaticExtension.cs b/src/Controls/src/Xaml/MarkupExtensions/StaticExtension.cs
@@ -28,7 +28,7 @@ public object ProvideValue(IServiceProvider serviceProvider)
 
 			var pinfo = type.GetRuntimeProperties().FirstOrDefault(pi => pi.Name == membername && pi.GetMethod.IsStatic);
 			if (pinfo != null)
-				return pinfo.GetMethod.Invoke(null, new object[] { });
+				return pinfo.GetMethod.Invoke(null, Array.Empty<object>());
 
 			var finfo = type.GetRuntimeFields().FirstOrDefault(fi => fi.Name == membername && fi.IsStatic);
 			if (finfo != null)

diff --git a/src/Controls/tests/Core.UnitTests/BindableLayoutTests.cs b/src/Controls/tests/Core.UnitTests/BindableLayoutTests.cs
@@ -369,7 +369,7 @@ public void ValidateBindableProperties()
 
 
 			// ItemsSourceProperty
-			IEnumerable itemsSource = new object[0];
+			IEnumerable itemsSource = Array.Empty<object>();
 			BindableLayout.SetItemsSource(layout, itemsSource);
 
 			Assert.Equal(itemsSource, BindableLayout.GetItemsSource(layout));

diff --git a/src/Controls/tests/Core.UnitTests/BindingBaseUnitTests.cs b/src/Controls/tests/Core.UnitTests/BindingBaseUnitTests.cs
@@ -696,9 +696,9 @@ public void EnableCollectionSynchronizationInvalid()
 		{
 			Assert.Throws<ArgumentNullException>(() => BindingBase.EnableCollectionSynchronization(null, new object(),
 			   (collection, context, method, access) => { }));
-			Assert.Throws<ArgumentNullException>(() => BindingBase.EnableCollectionSynchronization(new string[0], new object(), null));
+			Assert.Throws<ArgumentNullException>(() => BindingBase.EnableCollectionSynchronization(Array.Empty<string>(), new object(), null));
 
-			BindingBase.EnableCollectionSynchronization(new string[0], null, (collection, context, method, access) => { });
+			BindingBase.EnableCollectionSynchronization(Array.Empty<string>(), null, (collection, context, method, access) => { });
 		}
 
 		[Fact]