[Xaml] Simplify loading ResourceDictionary from Source

src/Controls/src/Core/ResourceDictionary.cs

@@ -34,7 +34,7 @@ public Uri Source
 			{
 				if (_source == value)
 					return;
-				throw new InvalidOperationException("Source can only be set from XAML."); //through the RDSourceTypeConverter
+				throw new InvalidOperationException("Source can only be set from XAML."); // through SetSource
 			}
 		}
 
@@ -50,24 +50,19 @@ public void SetAndLoadSource(Uri value, string resourcePath, Assembly assembly,
 			if (type != null)
 			{
 				_mergedInstance = s_instances.GetValue(type, _ => (ResourceDictionary)Activator.CreateInstance(type));
+				OnValuesChanged(_mergedInstance.ToArray());
 			}
-			else
-			{
-				if (RuntimeFeature.IsXamlRuntimeParsingSupported)
-				{
-					_mergedInstance = DependencyService.Get<IResourcesLoader>().CreateFromResource<ResourceDictionary>(resourcePath, assembly, lineInfo);
-				}
-				else
-				{
-					// This codepath is only ever hit when XamlC is explicitly disabled for a given resource dictionary.
-					// The developer had to add [XamlCompilation(XamlCompilationOptions.Skip)] or <?xaml-comp compile="false" ?> to their code.
-					// XamlC will produce a warning in this case (MAUIG0070 or XC0010).
-					throw new InvalidOperationException(
-						$"The resource '{resourcePath}' has not been compiled using XamlC and parsing XAML resources at runtime is disabled. "
-						+ "Ensure the resource is compiled using XamlC. Alternatively, enable parsing XAML resources at runtime by setting "
-						+ "the MauiXamlRuntimeParsingSupport MSBuild property to true.");
-				}
-			}
+		}
+
+		internal static ResourceDictionary GetOrCreateInstance([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)] Type type)
+		{
+			return s_instances.GetValue(type, _ => (ResourceDictionary)Activator.CreateInstance(type));
+		}
+
+		internal void SetSource(Uri source, ResourceDictionary sourceInstance)
+		{
+			_source = source;
+			_mergedInstance = sourceInstance;
 			OnValuesChanged(_mergedInstance.ToArray());
 		}
 
@@ -396,26 +391,29 @@ object IExtendedTypeConverter.ConvertFromInvariantString(string value, IServiceP
 				if (rootObjectType == null)
 					return null;
 
-				var lineInfo = (serviceProvider.GetService(typeof(Xaml.IXmlLineInfoProvider)) as Xaml.IXmlLineInfoProvider)?.XmlLineInfo;
-				var rootTargetPath = XamlResourceIdAttribute.GetPathForType(rootObjectType);
-				var assembly = rootObjectType.Assembly;
+				return GetUriWithExplicitAssembly(value, rootObjectType.Assembly);
+			}
+
+			internal static Uri GetUriWithExplicitAssembly(string value, Assembly defaultAssembly)
+			{
+				(value, var assembly) = SplitUriAndAssembly(value, defaultAssembly);
+				return CombineUriAndAssembly(value, assembly);
+			}
 
+			internal static ValueTuple<string, Assembly> SplitUriAndAssembly(string value, Assembly defaultAssembly)
+			{
 				if (value.IndexOf(";assembly=", StringComparison.Ordinal) != -1)
 				{
 					var parts = value.Split(new[] { ";assembly=" }, StringSplitOptions.RemoveEmptyEntries);
-					value = parts[0];
-					var asmName = parts[1];
-					assembly = Assembly.Load(asmName);
+					return (parts[0], Assembly.Load(parts[1]));
 				}
 
-				var uri = new Uri(value, UriKind.Relative); //we don't want file:// uris, even if they start with '/'
-				var resourcePath = GetResourcePath(uri, rootTargetPath);
-
-				//Re-add the assembly= in all cases, so HotReload doesn't have to make assumptions
-				uri = new Uri($"{value};assembly={assembly.GetName().Name}", UriKind.Relative);
-				targetRD.SetAndLoadSource(uri, resourcePath, assembly, lineInfo);
+				return (value, defaultAssembly);
+			}
 
-				return uri;
+			internal static Uri CombineUriAndAssembly(string value, Assembly assembly)
+			{
+				return new Uri($"{value};assembly={assembly.GetName().Name}", UriKind.Relative);
 			}
 
 			internal static string GetResourcePath(Uri uri, string rootTargetPath)

src/Controls/src/Core/StyleSheets/StyleSheet.cs

@@ -7,6 +7,8 @@
 using System.Runtime.CompilerServices;
 using System.Xml;
 
+using Microsoft.Maui.Controls.Xaml;
+
 namespace Microsoft.Maui.Controls.StyleSheets
 {
 	/// <include file="../../../docs/Microsoft.Maui.Controls.StyleSheets/StyleSheet.xml" path="Type[@FullName='Microsoft.Maui.Controls.StyleSheets.StyleSheet']/Docs/*" />
@@ -24,7 +26,7 @@ public sealed class StyleSheet : IStyle
 		public static StyleSheet FromResource(string resourcePath, Assembly assembly, IXmlLineInfo lineInfo = null)
 		{
 			var styleSheet = new StyleSheet();
-			var resString = DependencyService.Get<IResourcesLoader>().GetResource(resourcePath, assembly, styleSheet, lineInfo);
+			var resString = GetResource(resourcePath, assembly, styleSheet, lineInfo);
 			using (var textReader = new StringReader(resString))
 			using (var cssReader = new CssReader(textReader))
 				Parse(styleSheet, cssReader);
@@ -114,5 +116,31 @@ void Apply(Element styleable)
 		}
 
 		void IStyle.UnApply(BindableObject bindable) => throw new NotImplementedException();
+
+		private static string GetResource(string resourcePath, Assembly assembly, object target, IXmlLineInfo lineInfo)
+		{
+			var resourceLoadingResponse = Maui.Controls.Internals.ResourceLoader.ResourceProvider2?.Invoke(new Maui.Controls.Internals.ResourceLoader.ResourceLoadingQuery
+			{
+				AssemblyName = assembly.GetName(),
+				ResourcePath = resourcePath,
+				Instance = target
+			});
+
+			var alternateResource = resourceLoadingResponse?.ResourceContent;
+			if (alternateResource != null)
+				return alternateResource;
+
+			var resourceId = XamlResourceIdAttribute.GetResourceIdForPath(assembly, resourcePath);
+			if (resourceId == null)
+				throw new XamlParseException($"Resource '{resourcePath}' not found.", lineInfo);
+
+			using (var stream = assembly.GetManifestResourceStream(resourceId))
+			{
+				if (stream == null)
+					throw new XamlParseException($"No resource found for '{resourceId}'.", lineInfo);
+				using (var reader = new StreamReader(stream))
+					return reader.ReadToEnd();
+			}
+		}
 	}
 }

src/Controls/src/Xaml/ApplyPropertiesVisitor.cs

@@ -370,6 +370,13 @@ public static void SetPropertyValue(object xamlelement, XmlName propertyName, ob
 			var serviceProvider = new XamlServiceProvider(node, context);
 			var xKey = node is IElementNode eNode && eNode.Properties.ContainsKey(XmlName.xKey) ? ((ValueNode)eNode.Properties[XmlName.xKey]).Value as string : null;
 
+			// Special handling for ResourceDictionary.Source
+			if (xamlelement is ResourceDictionary rd && propertyName.LocalName == "Source" && propertyName.NamespaceURI == "")
+			{
+				ResourceDictionaryHelpers.LoadFromSource(rd, (string)value, rootElement.GetType(), lineInfo);
+				return;
+			}
+
 			if (TrySetPropertyValue(xamlelement, propertyName, xKey, value, rootElement, lineInfo, serviceProvider, out var xpe))
 				return;
 

src/Controls/src/Xaml/CreateValuesVisitor.cs

@@ -56,17 +56,23 @@ public void Visit(ElementNode node, INode parentNode)
 			}
 			Context.Types[node] = type;
 			if (IsXaml2009LanguagePrimitive(node))
+			{
 				value = CreateLanguagePrimitive(type, node);
+			}
 			else if (node.Properties.ContainsKey(XmlName.xArguments) || node.Properties.ContainsKey(XmlName.xFactoryMethod))
+			{
 				value = CreateFromFactory(type, node);
+			}
 			else if (
 				type.GetTypeInfo()
 					.DeclaredConstructors.Any(
 						ci =>
 							ci.IsPublic && ci.GetParameters().Length != 0 &&
 							ci.GetParameters().All(pi => pi.CustomAttributes.Any(attr => attr.AttributeType == typeof(ParameterAttribute)))) &&
 				ValidateCtorArguments(type, node, out string ctorargname))
+			{
 				value = CreateFromParameterizedConstructor(type, node);
+			}
 			else if (!type.GetTypeInfo().DeclaredConstructors.Any(ci => ci.IsPublic && ci.GetParameters().Length == 0) &&
 					 !ValidateCtorArguments(type, node, out ctorargname))
 			{

src/Controls/src/Xaml/Hosting/AppHostBuilderExtensions.cs

@@ -166,7 +166,6 @@ static MauiAppBuilder SetupDefaults(this MauiAppBuilder builder)
 #if WINDOWS || ANDROID || IOS || MACCATALYST || TIZEN
 			// initialize compatibility DependencyService
 			DependencyService.SetToInitialized();
-			DependencyService.Register<Xaml.ResourcesLoader>();
 			DependencyService.Register<Xaml.ValueConverterProvider>();
 			DependencyService.Register<PlatformSizeService>();
 

src/Controls/src/Xaml/ResourceDictionaryHelpers.cs

@@ -0,0 +1,60 @@
+using System;
+using System.IO;
+using System.Reflection;
+using System.Xml;
+
+namespace Microsoft.Maui.Controls.Xaml
+{
+	internal static class ResourceDictionaryHelpers
+	{
+		internal static void LoadFromSource(ResourceDictionary rd, string value, Type rootType, IXmlLineInfo lineInfo)
+		{
+			(value, var assembly) = ResourceDictionary.RDSourceTypeConverter.SplitUriAndAssembly(value, rootType.Assembly);
+
+			var rootTargetPath = XamlResourceIdAttribute.GetPathForType(rootType);
+			var resourcePath = ResourceDictionary.RDSourceTypeConverter.GetResourcePath(new Uri(value, UriKind.Relative), rootTargetPath);
+			var sourceUri = ResourceDictionary.RDSourceTypeConverter.CombineUriAndAssembly(value, assembly);
+
+			var type = XamlResourceIdAttribute.GetTypeForPath(assembly, resourcePath);
+			var sourceInstance = type is not null
+				? ResourceDictionary.GetOrCreateInstance(type)
+				: CreateFromResource(resourcePath, assembly, lineInfo);
+
+			rd.SetSource(sourceUri, sourceInstance);
+
+			static ResourceDictionary CreateFromResource(string resourcePath, Assembly assembly, IXmlLineInfo lineInfo)
+			{
+				var rd = new ResourceDictionary();
+
+				var resourceLoadingResponse = Maui.Controls.Internals.ResourceLoader.ResourceProvider2?.Invoke(new Maui.Controls.Internals.ResourceLoader.ResourceLoadingQuery
+				{
+					AssemblyName = assembly.GetName(),
+					ResourcePath = resourcePath,
+					Instance = rd,
+				});
+
+				var alternateResource = resourceLoadingResponse?.ResourceContent;
+				if (alternateResource != null)
+				{
+					XamlLoader.Load(rd, alternateResource, resourceLoadingResponse.UseDesignProperties);
+					return rd;
+				}
+
+				var resourceId = XamlResourceIdAttribute.GetResourceIdForPath(assembly, resourcePath);
+				if (resourceId == null)
+					throw new XamlParseException($"Resource '{resourcePath}' not found.", lineInfo);
+
+				using (var stream = assembly.GetManifestResourceStream(resourceId))
+				{
+					if (stream == null)
+						throw new XamlParseException($"No resource found for '{resourceId}'.", lineInfo);
+					using (var reader = new StreamReader(stream))
+					{
+						rd.LoadFromXaml(reader.ReadToEnd(), assembly);
+						return rd;
+					}
+				}
+			}
+		}
+	}
+}