[XSG] Skip compiled binding when RelativeSource is used

src/Controls/src/SourceGen/KnownMarkups.cs

@@ -308,7 +308,16 @@ private static bool ProvideValueForBindingExtension(ElementNode markupNode, Inde
 	{
 		returnType = context.Compilation.GetTypeByMetadataName("Microsoft.Maui.Controls.BindingBase")!;
 		ITypeSymbol? dataTypeSymbol = null;
-		if (   context.Variables.TryGetValue(markupNode, out ILocalValue extVariable)
+
+		// Check if the binding has a Source property with a RelativeSource.
+		// In this case, we should NOT compile the binding using x:DataType because
+		// the source type will be determined at runtime by the RelativeSource, not x:DataType.
+		bool hasRelativeSource = HasRelativeSourceBinding(markupNode);
+
+		context.Variables.TryGetValue(markupNode, out ILocalValue? extVariable);
+
+		if (   !hasRelativeSource
+			&& extVariable is not null
 			&& TryGetXDataType(markupNode, context, out dataTypeSymbol)
 			&& dataTypeSymbol is not null)
 		{
@@ -588,6 +597,29 @@ static bool IsBindingContextBinding(ElementNode node)
 				&& propertyName.NamespaceURI == ""
 				&& propertyName.LocalName == "BindingContext";
 		}
+
+		// Checks if the binding has a Source property that is a RelativeSource extension.
+		// When a binding uses RelativeSource, the source type is determined at runtime,
+		// so we should NOT compile the binding using x:DataType.
+		static bool HasRelativeSourceBinding(ElementNode bindingNode)
+		{
+			// Check if Source property exists
+			if (!bindingNode.Properties.TryGetValue(new XmlName("", "Source"), out INode? sourceNode)
+				&& !bindingNode.Properties.TryGetValue(new XmlName(null, "Source"), out sourceNode))
+			{
+				return false;
+			}
+
+			// Check if the Source is a RelativeSourceExtension
+			if (sourceNode is ElementNode sourceElementNode)
+			{
+				// Check if the element is a RelativeSourceExtension
+				return sourceElementNode.XmlType.Name == "RelativeSourceExtension"
+					|| sourceElementNode.XmlType.Name == "RelativeSource";
+			}
+
+			return false;
+		}
 	}
 
 	internal static bool ProvideValueForDataTemplateExtension(ElementNode markupNode, IndentedTextWriter writer, SourceGenContext context, NodeSGExtensions.GetNodeValueDelegate? getNodeValue, out ITypeSymbol? returnType, out string value)

src/Controls/tests/SourceGen.UnitTests/InitializeComponent/RelativeSourceBindings.cs

@@ -281,4 +281,125 @@ public class TestViewModel
 		Assert.Contains("RelativeBindingSource", generated, StringComparison.Ordinal);
 		Assert.Contains("FindAncestorBindingContext", generated, StringComparison.Ordinal);
 	}
+
+	[Fact]
+	public void SelfPathWithFindAncestorGeneratesValidCode()
+	{
+		// Test for regression: RelativeSource AncestorType with Path=. should return the ancestor itself
+		var xaml =
+"""
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage
+	xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+	xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+	x:Class="Test.TestPage">
+	<Grid>
+		<Grid.GestureRecognizers>
+			<TapGestureRecognizer Command="{Binding Navigate}"
+				CommandParameter="{Binding Path=., Source={RelativeSource AncestorType={x:Type ContentPage}}}" />
+		</Grid.GestureRecognizers>
+	</Grid>
+</ContentPage>
+""";
+
+		var code =
+"""
+#nullable enable
+using System.Windows.Input;
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Test;
+
+[XamlProcessing(XamlInflator.SourceGen)]
+public partial class TestPage : ContentPage
+{
+	public TestPage()
+	{
+		InitializeComponent();
+		BindingContext = this;
+	}
+
+	public ICommand Navigate => new Command((param) => { });
+}
+""";
+
+		var (result, generated) = RunGenerator(xaml, code);
+
+		// Verify no diagnostics
+		Assert.False(result.Diagnostics.Any(d => d.Severity == Microsoft.CodeAnalysis.DiagnosticSeverity.Error),
+			$"Generator produced errors: {string.Join(", ", result.Diagnostics.Where(d => d.Severity == Microsoft.CodeAnalysis.DiagnosticSeverity.Error).Select(d => d.GetMessage()))}");
+
+		// Verify generated code exists
+		Assert.NotNull(generated);
+
+		// Verify RelativeBindingSource is generated correctly with FindAncestor mode (ContentPage is an Element)
+		Assert.Contains("RelativeBindingSource", generated, StringComparison.Ordinal);
+		Assert.Contains("FindAncestor", generated, StringComparison.Ordinal);
+		Assert.Contains("ContentPage", generated, StringComparison.Ordinal);
+	}
+
+	[Fact]
+	public void SelfPathWithFindAncestorCustomTypeGeneratesValidCode()
+	{
+		// Test for regression: RelativeSource AncestorType with Path=. and custom page type
+		// This replicates the user's scenario where MainPage is a custom type
+		var xaml =
+"""
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentView
+	xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+	xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+	xmlns:test="clr-namespace:Test"
+	x:Class="Test.ChildView"
+	x:DataType="test:ChildView">
+	<Grid>
+		<Grid.GestureRecognizers>
+			<TapGestureRecognizer Command="{Binding Navigate}"
+				CommandParameter="{Binding Path=., Source={RelativeSource AncestorType={x:Type test:MainPage}}}" />
+		</Grid.GestureRecognizers>
+	</Grid>
+</ContentView>
+""";
+
+		var code =
+"""
+#nullable enable
+using System.Windows.Input;
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Test;
+
+[XamlProcessing(XamlInflator.SourceGen)]
+public partial class ChildView : ContentView
+{
+	public ChildView()
+	{
+		InitializeComponent();
+		BindingContext = this;
+	}
+
+	public ICommand Navigate => new Command((param) => { });
+}
+
+public class MainPage : ContentPage
+{
+}
+""";
+
+		var (result, generated) = RunGenerator(xaml, code);
+
+		// Verify no diagnostics
+		Assert.False(result.Diagnostics.Any(d => d.Severity == Microsoft.CodeAnalysis.DiagnosticSeverity.Error),
+			$"Generator produced errors: {string.Join(", ", result.Diagnostics.Where(d => d.Severity == Microsoft.CodeAnalysis.DiagnosticSeverity.Error).Select(d => d.GetMessage()))}");
+
+		// Verify generated code exists
+		Assert.NotNull(generated);
+
+		// Verify RelativeBindingSource is generated correctly with FindAncestor mode and custom type
+		Assert.Contains("RelativeBindingSource", generated, StringComparison.Ordinal);
+		Assert.Contains("FindAncestor", generated, StringComparison.Ordinal);
+		Assert.Contains("Test.MainPage", generated, StringComparison.Ordinal);
+	}
 }

src/Controls/tests/Xaml.UnitTests/Issues/Maui33247.xaml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:local="clr-namespace:Microsoft.Maui.Controls.Xaml.UnitTests"
+    x:Class="Microsoft.Maui.Controls.Xaml.UnitTests.Maui33247"
+    x:DataType="local:Maui33247">
+    <!-- Test: RelativeSource AncestorType with Path=. should return the ContentPage itself -->
+    <Grid x:Name="MainGrid" BackgroundColor="Blue">
+        <Grid.GestureRecognizers>
+            <TapGestureRecognizer x:Name="DirectTapGesture" 
+                Command="{Binding Navigate}"
+                CommandParameter="{Binding Path=., Source={RelativeSource AncestorType={x:Type local:Maui33247}}}" />
+        </Grid.GestureRecognizers>
+        <Label Text="Direct binding test" />
+    </Grid>
+</ContentPage>

src/Controls/tests/Xaml.UnitTests/Issues/Maui33247.xaml.cs

@@ -0,0 +1,46 @@
+using System.Windows.Input;
+using Xunit;
+
+namespace Microsoft.Maui.Controls.Xaml.UnitTests;
+
+/// <summary>
+/// Test for regression: RelativeSource AncestorType with Path=. returns null in v10.0.20
+/// 
+/// Scenario: A TapGestureRecognizer tries to get a reference to the parent ContentPage via
+/// CommandParameter="{Binding Path=., Source={RelativeSource AncestorType={x:Type local:Maui33247}}}"
+/// 
+/// Expected: The CommandParameter should receive the ContentPage reference.
+/// Bug: In v10.0.20, the CommandParameter was null when using SourceGen because the source generator
+/// was incorrectly compiling the binding to use x:DataType as the source type instead of allowing
+/// the RelativeSource to resolve the source at runtime.
+/// 
+/// Fix: When a binding has a Source property with a RelativeSource, skip the compiled binding path
+/// and use the fallback string-based binding instead.
+/// </summary>
+public partial class Maui33247 : ContentPage
+{
+	public Maui33247()
+	{
+		InitializeComponent();
+		BindingContext = this;
+	}
+
+	public ICommand Navigate => new Command((param) => { });
+
+	[Collection("Issue")]
+	public class Tests
+	{
+		[Theory]
+		[XamlInflatorData]
+		internal void DirectRelativeSourceAncestorTypeWithSelfPathReturnsAncestor(XamlInflator inflator)
+		{
+			// Test that RelativeSource AncestorType with Path=. returns the ancestor object for direct children
+			var page = new Maui33247(inflator);
+
+			// The CommandParameter with RelativeSource AncestorType and Path=. should be the ContentPage itself
+			Assert.NotNull(page.DirectTapGesture.CommandParameter);
+			Assert.IsType<Maui33247>(page.DirectTapGesture.CommandParameter);
+			Assert.Same(page, page.DirectTapGesture.CommandParameter);
+		}
+	}
+}