fix: Workaround Android/iOS HR issues

src/SourceGenerators/Uno.UI.SourceGenerators.Tests/MetadataUpdates/HotReloadWorkspaceProvider.cs

@@ -21,8 +21,15 @@ internal class HotReloadWorkspace
 {
 	public record UpdateResult(ImmutableArray<Diagnostic> Diagnostics, ImmutableArray<WatchHotReloadService.Update> MetadataUpdates);
 
-	const string NetCoreCapsRaw = "Baseline AddMethodToExistingType AddStaticFieldToExistingType AddInstanceFieldToExistingType NewTypeDefinition ChangeCustomAttributes UpdateParameters";
-	const string MonoCapsRaw = "Baseline AddMethodToExistingType AddStaticFieldToExistingType NewTypeDefinition ChangeCustomAttributes";
+#if NET8_0
+	const string NetCoreCapsRaw = "Baseline AddMethodToExistingType AddStaticFieldToExistingType NewTypeDefinition ChangeCustomAttributes AddInstanceFieldToExistingType GenericAddMethodToExistingType GenericUpdateMethod UpdateParameters GenericAddFieldToExistingType";
+	const string MonoCapsRaw = "Baseline AddMethodToExistingType AddStaticFieldToExistingType NewTypeDefinition ChangeCustomAttributes AddInstanceFieldToExistingType GenericAddMethodToExistingType GenericUpdateMethod UpdateParameters GenericAddFieldToExistingType";
+#elif NET9_0
+const string NetCoreCapsRaw = "Baseline AddMethodToExistingType AddStaticFieldToExistingType NewTypeDefinition ChangeCustomAttributes AddInstanceFieldToExistingType GenericAddMethodToExistingType GenericUpdateMethod UpdateParameters GenericAddFieldToExistingType";
+	const string MonoCapsRaw = "Baseline AddMethodToExistingType AddStaticFieldToExistingType NewTypeDefinition ChangeCustomAttributes AddInstanceFieldToExistingType GenericAddMethodToExistingType GenericUpdateMethod UpdateParameters GenericAddFieldToExistingType";
+#else
+#error Capabilities should be defined for the updated target framework.
+#endif
 
 	private readonly string _baseWorkFolder;
 	private readonly bool _isDebugCompilation;
@@ -371,7 +378,7 @@ private static PortableExecutableReference[] BuildUnoReferences()
 #endif
 
 		var availableTargets = new[] {
-			Path.Combine("Uno.UI.Skia", configuration, "8.0"),
+			Path.Combine("Uno.UI.Skia", configuration, "net8.0"),
 			Path.Combine("Uno.UI.Reference", configuration, "net8.0"),
 			Path.Combine("Uno.UI.Tests", configuration, "net8.0"),
 		};

src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlCodeGeneration.cs

@@ -143,6 +143,8 @@ private bool IsUnoFluentAssembly
 
 		internal ImmutableArray<ITypeProvider> TypeProviders { get; }
 
+		internal bool IsSkia { get; }
+
 		public XamlCodeGeneration(GeneratorExecutionContext context)
 		{
 			// To easily debug XAML code generation:
@@ -260,6 +262,7 @@ public XamlCodeGeneration(GeneratorExecutionContext context)
 			_defaultNamespace = context.GetMSBuildPropertyValue("RootNamespace");
 
 			_isWasm = context.GetMSBuildPropertyValue("DefineConstantsProperty")?.Contains("__WASM__") ?? false;
+			IsSkia = context.GetMSBuildPropertyValue("DefineConstantsProperty")?.Contains("__SKIA__") ?? false;
 			_isDesignTimeBuild = Helpers.DesignTimeHelper.IsDesignTime(context);
 
 			StringSymbol = GetSpecialTypeSymbolAsLazy(SpecialType.System_String);
@@ -686,9 +689,10 @@ private SourceText GenerateGlobalResources(IEnumerable<XamlFileDefinition> files
 				writer.AppendLineIndented("/// Contains all the static resources defined for the application");
 				writer.AppendLineIndented("/// </summary>");
 
-				if (_isDebug)
+				if (_isDebug && !IsSkia)
 				{
-					//writer.AppendLineIndented("[global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdate]");
+					// On Skia, we don't use CreateNewOnMetadataUpdate at all.
+					writer.AppendLineIndented("[global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdate]");
 				}
 
 				AnalyzerSuppressionsGenerator.Generate(writer, _analyzerSuppressions);

src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.Reflection.cs

@@ -178,19 +178,19 @@ private bool IsFrameworkElement(XamlType xamlType)
 			return IsType(xamlType, Generation.FrameworkElementSymbol.Value);
 		}
 
-		private bool IsAndroidView(XamlType xamlType)
+		private bool IsAndroidView(INamedTypeSymbol? type)
 		{
-			return IsType(xamlType, Generation.AndroidViewSymbol.Value);
+			return IsType(type, Generation.AndroidViewSymbol.Value);
 		}
 
-		private bool IsIOSUIView(XamlType xamlType)
+		private bool IsIOSUIView(INamedTypeSymbol? type)
 		{
-			return IsType(xamlType, Generation.IOSViewSymbol.Value);
+			return IsType(type, Generation.IOSViewSymbol.Value);
 		}
 
-		private bool IsMacOSNSView(XamlType xamlType)
+		private bool IsMacOSNSView(INamedTypeSymbol? type)
 		{
-			return IsType(xamlType, Generation.AppKitViewSymbol.Value);
+			return IsType(type, Generation.AppKitViewSymbol.Value);
 		}
 
 		private bool IsDependencyObject(XamlObjectDefinition component)
@@ -205,7 +205,9 @@ private bool IsUIElement(INamedTypeSymbol? symbol)
 		/// <summary>
 		/// Is the type derived from the native view type on a Xamarin platform?
 		/// </summary>
-		private bool IsNativeView(XamlType xamlType) => IsAndroidView(xamlType) || IsIOSUIView(xamlType) || IsMacOSNSView(xamlType);
+		private bool IsNativeView(XamlType xamlType) => IsNativeView(FindType(xamlType));
+
+		private bool IsNativeView(INamedTypeSymbol? type) => IsAndroidView(type) || IsIOSUIView(type) || IsMacOSNSView(type);
 
 		/// <summary>
 		/// Is the type one of the base view types in WinUI? (UIElement is most commonly used to mean 'any WinUI view type,' but

src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlFileGenerator.cs

@@ -372,7 +372,7 @@ private SourceText InnerGenerateFile()
 
 					var controlBaseType = GetType(topLevelControl.Type);
 
-					WriteMetadataNewTypeAttribute(writer);
+					WriteMetadataNewTypeAttributeOnMarkerIfNativeView(writer, controlBaseType);
 
 					using (writer.BlockInvariant("partial class {0} : {1}", _xClassName.ClassName, controlBaseType.GetFullyQualifiedTypeIncludingGlobal()))
 					{
@@ -1396,9 +1396,35 @@ IDisposable WrapSingleton()
 
 		private void WriteMetadataNewTypeAttribute(IIndentedStringBuilder writer)
 		{
-			if (_isHotReloadEnabled)
+			if (_isHotReloadEnabled && !Generation.IsSkia)
+			{
+				// On Skia, we don't use CreateNewOnMetadataUpdate at all.
+				writer.AppendLineIndented("[global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdate]");
+			}
+		}
+
+		private void WriteMetadataNewTypeAttributeOnMarkerIfNativeView(IIndentedStringBuilder writer, INamedTypeSymbol originalType)
+		{
+			if (!_isHotReloadEnabled || Generation.IsSkia)
+			{
+				return;
+			}
+
+			if (IsNativeView(originalType))
+			{
+				var originalTypeFullyQualified = originalType.GetFullyQualifiedTypeIncludingGlobal();
+				// On non-Skia, we add the attribute to the marker class when the type is a native view
+				writer.AppendLineIndented("[global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdate]");
+				writer.AppendLineIndented($"[global::Uno.Foundation.UnoOriginalType(typeof({originalTypeFullyQualified}))]");
+				using (writer.BlockInvariant($"internal sealed class __Uno_HotReload_Marker_{originalType.Name}_{_fileDefinition.UniqueID}_{HashBuilder.Build(originalTypeFullyQualified)}"))
+				{
+					writer.AppendLineIndented($"private const string HashCode = \"{_fileDefinition.Checksum}\";");
+				}
+			}
+			else
 			{
-				//writer.AppendLineIndented("[global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdate]");
+				// On non-Skia, we add the attribute directly if the type is not a native view
+				writer.AppendLineIndented("[global::System.Runtime.CompilerServices.CreateNewOnMetadataUpdate]");
 			}
 		}
 
@@ -3824,12 +3850,13 @@ private void BuildUiAutomationId(IIndentedStringBuilder writer, string closureNa
 			writer.AppendLineInvariantIndented("// UI automation id: {0}", uiAutomationId);
 
 			// ContentDescription and AccessibilityIdentifier are used by Xamarin.UITest (Test Cloud) to identify visual elements
-			if (IsAndroidView(parent.Type))
+			var parentType = FindType(parent.Type);
+			if (IsAndroidView(parentType))
 			{
 				writer.AppendLineInvariantIndented("{0}.ContentDescription = \"{1}\";", closureName, uiAutomationId);
 			};
 
-			if (IsIOSUIView(parent.Type))
+			if (IsIOSUIView(parentType))
 			{
 				writer.AppendLineInvariantIndented("{0}.AccessibilityIdentifier = \"{1}\";", closureName, uiAutomationId);
 			}

src/Uno.Foundation/Internal/UnoOriginalTypeAttribute.cs

@@ -0,0 +1,18 @@
+using System.ComponentModel;
+
+namespace Uno.Foundation;
+
+/// <summary>
+/// This attribute is used by XAML generator for HotReload purposes.
+/// External users should not use this attribute.
+/// </summary>
+[EditorBrowsable(EditorBrowsableState.Never)]
+public sealed class UnoOriginalTypeAttribute : Attribute
+{
+	public UnoOriginalTypeAttribute(Type type)
+	{
+		OriginalType = type;
+	}
+
+	public Type OriginalType { get; }
+}

src/Uno.UI.RemoteControl/HotReload/ClientHotReloadProcessor.PartialReload.cs

@@ -2,16 +2,17 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.Loader;
 using System.Text;
 using System.Threading.Tasks;
 using Uno.Extensions;
+using Uno.Foundation;
 using Uno.Foundation.Logging;
 using Uno.UI.RemoteControl.HotReload.Messages;
-using System.Runtime.Loader;
-using System.Runtime.CompilerServices;
-using System.Diagnostics;
 
 namespace Uno.UI.RemoteControl.HotReload
 {
@@ -189,7 +190,7 @@ where debuggableAttribute is not null
 					from type in asm.GetTypes()
 					let originalType = type.GetCustomAttribute<MetadataUpdateOriginalTypeAttribute>()
 					where originalType is not null
-					group type by originalType.OriginalType into g
+					group type by GetOriginalType(type, originalType.OriginalType) into g
 					select new
 					{
 						Key = g.Key.FullName,
@@ -199,5 +200,14 @@ group type by originalType.OriginalType into g
 
 			return mappedTypes.ToDictionary(p => p.Key, p => p.LastMapped);
 		}
+
+		private static Type GetOriginalType(Type type, Type originalType)
+			// Normally, HotReload should work by reading the original type from MetadataUpdateOriginalTypeAttribute.
+			// It's currently a problem on Android and iOS that a new type can't be emitted as it ends up with two managed types pointing to the same native type.
+			// For this reason, we create a fake marker class with CreateNewOnMetadataUpdate attribute.
+			// The marker class has UnoOriginalTypeAttribute which points to the real original type.
+			// So, when we update the marker class, we should use the OriginalType specified by it.
+			// Otherwise, use the original type from MetadataUpdateOriginalTypeAttribute
+			=> type.GetCustomAttribute<UnoOriginalTypeAttribute>()?.OriginalType ?? originalType;
 	}
 }