feat(styles): Populate ThemeDictionaries defined in XAML

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

@@ -777,6 +777,7 @@ private void InitializeAndBuildResourceDictionary(IIndentedStringBuilder writer,
 			writer.AppendLineInvariant("new ResourceDictionary {{");
 			BuildResourceDictionary(writer, FindImplicitContentMember(topLevelControl), isInInitializer: true);
 			BuildMergedDictionaries(writer, topLevelControl.Members.FirstOrDefault(m => m.Member.Name == "MergedDictionaries"), isInInitializer: true);
+			BuildThemeDictionaries(writer, topLevelControl.Members.FirstOrDefault(m => m.Member.Name == "ThemeDictionaries"), isInInitializer: true);
 			writer.AppendLineInvariant("}}");
 		}
 
@@ -2054,6 +2055,12 @@ private void RegisterAndBuildResources(IIndentedStringBuilder writer, XamlObject
 							.Where(m => m.Member.Name == "MergedDictionaries")
 							.FirstOrDefault()
 					: null;
+				var themeDictionaries = isExplicitResDictionary ?
+					resourcesMember.Objects
+						.First().Members
+							.Where(m => m.Member.Name == "ThemeDictionaries")
+							.FirstOrDefault()
+					: null;
 
 				if (resourcesRoot != null || mergedDictionaries != null)
 				{
@@ -2063,8 +2070,8 @@ private void RegisterAndBuildResources(IIndentedStringBuilder writer, XamlObject
 					}
 
 					BuildResourceDictionary(writer, resourcesRoot, isInInitializer);
-
 					BuildMergedDictionaries(writer, mergedDictionaries, isInInitializer);
+					BuildThemeDictionaries(writer, themeDictionaries, isInInitializer);
 
 					if (isInInitializer)
 					{
@@ -2139,6 +2146,23 @@ private void BuildResourceDictionary(IIndentedStringBuilder writer, XamlMemberDe
 		/// Populate MergedDictionaries property of a ResourceDictionary.
 		/// </summary>
 		private void BuildMergedDictionaries(IIndentedStringBuilder writer, XamlMemberDefinition mergedDictionaries, bool isInInitializer)
+		{
+			var propertyName = "MergedDictionaries";
+			BuildDictionaryCollection(writer, mergedDictionaries, isInInitializer, propertyName, isDict: false);
+		}
+
+		/// <summary>
+		/// Populate ThemeDictionaries property of a ResourceDictionary.
+		/// </summary>
+		private void BuildThemeDictionaries(IIndentedStringBuilder writer, XamlMemberDefinition themeDictionaries, bool isInInitializer)
+		{
+			BuildDictionaryCollection(writer, themeDictionaries, isInInitializer, "ThemeDictionaries", isDict: true);
+		}
+
+		/// <summary>
+		/// Build a collection of ResourceDictionaries.
+		/// </summary>
+		private void BuildDictionaryCollection(IIndentedStringBuilder writer, XamlMemberDefinition mergedDictionaries, bool isInInitializer, string propertyName, bool isDict)
 		{
 			if (mergedDictionaries == null)
 			{
@@ -2147,11 +2171,11 @@ private void BuildMergedDictionaries(IIndentedStringBuilder writer, XamlMemberDe
 
 			if (isInInitializer)
 			{
-				writer.AppendLineInvariant("MergedDictionaries = {{");
+				writer.AppendLineInvariant("{0} = {{", propertyName);
 			}
 			else
 			{
-				writer.AppendLineInvariant("// MergedDictionaries");
+				writer.AppendLineInvariant("// {0}", propertyName);
 			}
 			foreach (var dictObject in mergedDictionaries.Objects)
 			{
@@ -2161,18 +2185,33 @@ private void BuildMergedDictionaries(IIndentedStringBuilder writer, XamlMemberDe
 				}
 
 				var source = dictObject.Members.FirstOrDefault(m => m.Member.Name == "Source");
-				if (source != null && dictObject.Members.Count > 1)
+				if (source != null && dictObject.Members.Any(m => m.Member.Name == "_UnknownContent"))
 				{
 					throw new Exception("Local values are not allowed in resource dictionary with Source set");
 				}
 
-				if (!isInInitializer)
+				var key = dictObject.Members.FirstOrDefault(m => m.Member.Name == "Key")?.Value as string;
+				if (isDict && key == null)
+				{
+					throw new Exception("Each dictionary entry must have an associated key.");
+				}
+
+				if (!isInInitializer && !isDict)
 				{
-					writer.AppendLineInvariant("Resources.MergedDictionaries.Add(");
+					writer.AppendLineInvariant("Resources.{0}.Add(", propertyName);
 				}
+				else if (!isInInitializer && isDict)
+				{
+					writer.AppendLineInvariant("Resources.{0}[\"{1}\"] = ", propertyName, key);
+				}
+				else if (isInInitializer && isDict)
+				{
+					writer.AppendLineInvariant("[\"{0}\"] = ", key);
+				}
+
 				if (source != null)
 				{
-					BuildMergedDictionaryFromSource(writer, source, isInInitializer);
+					BuildDictionaryFromSource(writer, source, isInInitializer);
 				}
 				else
 				{
@@ -2182,10 +2221,14 @@ private void BuildMergedDictionaries(IIndentedStringBuilder writer, XamlMemberDe
 				{
 					writer.AppendLineInvariant(",");
 				}
-				else
+				else if (!isDict)
 				{
 					writer.AppendLineInvariant(");");
 				}
+				else
+				{
+					writer.AppendLineInvariant(";");
+				}
 			}
 
 			if (isInInitializer)
@@ -2195,9 +2238,9 @@ private void BuildMergedDictionaries(IIndentedStringBuilder writer, XamlMemberDe
 		}
 
 		/// <summary>
-		/// Try to create a MergedDictionary entry from supplied Source property.
+		/// Try to create a ResourceDictionary assignment from supplied Source property.
 		/// </summary>
-		private void BuildMergedDictionaryFromSource(IIndentedStringBuilder writer, XamlMemberDefinition sourceDef, bool isInInitializer)
+		private void BuildDictionaryFromSource(IIndentedStringBuilder writer, XamlMemberDefinition sourceDef, bool isInInitializer)
 		{
 			var source = (sourceDef?.Value as string)?.Replace('\\', '/');
 			if (source == null)

src/Uno.UI.Tests/App/App.xaml

@@ -18,6 +18,12 @@
 									 Color="Magenta" />
 				</ResourceDictionary>
 			</ResourceDictionary.MergedDictionaries>
+			<ResourceDictionary.ThemeDictionaries>
+				<ResourceDictionary x:Key="Light">
+					<SolidColorBrush x:Key="LucrativeColorBrush"
+									 Color="Azure" />
+				</ResourceDictionary>
+			</ResourceDictionary.ThemeDictionaries>
 		</ResourceDictionary>
 	</Application.Resources>
 

src/Uno.UI.Tests/App/Xaml/Test_Dictionary.xaml

@@ -9,6 +9,7 @@
 			<SolidColorBrush x:Key="PlayfulColorBrush"
 							 Color="RosyBrown" />
 		</ResourceDictionary>
+		<ResourceDictionary x:Key="Dark"  Source="Test_Dictionary_Theme.xaml" />
 	</ResourceDictionary.ThemeDictionaries>
 
 	<x:String x:Key="GlobalCoordinates">11.22, 33</x:String>

src/Uno.UI.Tests/App/Xaml/Test_Dictionary_Theme.xaml

@@ -0,0 +1,5 @@
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+					xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+	<SolidColorBrush x:Key="MoodyColorBrush"
+					 Color="DarkKhaki" />
+</ResourceDictionary>

src/Uno.UI.Tests/Uno.UI.Tests.csproj

@@ -99,7 +99,8 @@
 		<Page Include="App\Xaml\Test_CreateFromString.xaml" />
 		<Page Include="App\Xaml\Test_Dictionary.xaml" />
 		<Page Include="App\Xaml\Test_Dictionary_Inner.xaml" />
-		<Page Include="..\SamplesApp\UITests.Shared\Windows_UI_Xaml\Resources\Test_Dictionary_Linked.xaml" Link="App/Linked/Test_Dictionary_Linked.xaml"/>
+		<Page Include="App\Xaml\Test_Dictionary_Theme.xaml" />
+		<Page Include="..\SamplesApp\UITests.Shared\Windows_UI_Xaml\Resources\Test_Dictionary_Linked.xaml" Link="App/Linked/Test_Dictionary_Linked.xaml" />
 		<Page Include="App\Xaml\Test_Control.xaml" />
 		<Page Include="App\Xaml\Test_MarkupExtension.xaml" />
 	</ItemGroup>

src/Uno.UI.Tests/Windows_UI_Xaml/Given_ResourceDictionary.cs

@@ -374,8 +374,29 @@ public void When_Resource_In_Merged_Inline_Xaml()
 			AssertContainsColorBrushResource(app.Resources, "HangingOutInRecursiveMergedColorBrush", Colors.DarkMagenta);
 		}
 
+		[TestMethod]
+		public void When_Has_Themes_Inline_Xaml()
+		{
+			var app = UnitTestsApp.App.EnsureApplication();
+
+			AssertContainsColorBrushResource(app.Resources, "PlayfulColorBrush", Colors.RosyBrown);
+			AssertContainsColorBrushResource(app.Resources, "LucrativeColorBrush", Colors.Azure);
+		}
+
+		[TestMethod]
+		public void When_Has_Themes_Merged_Xaml()
+		{
+			var app = UnitTestsApp.App.EnsureApplication();
+
+			var dark = app.Resources.MergedDictionaries.First().ThemeDictionaries["Dark"] as ResourceDictionary;
+
+			AssertContainsColorBrushResource(dark, "MoodyColorBrush", Colors.DarkKhaki);
+		}
+
 		private void AssertContainsColorBrushResource(ResourceDictionary resources, string key, Color expected)
 		{
+			Assert.IsNotNull(resources);
+
 			var brush = resources[key] as SolidColorBrush;
 			Assert.IsNotNull(brush);
 			Assert.AreEqual(expected, brush.Color);