Enable Binding inteceptors source generator by default (#22856)

* Enable the BindingSourceGen analyzer by default * Improve filtering of SetBinding overloads * Add feature switch documentation * Revisit feature switch name * Update docs/design/FeatureSwitches.md Co-authored-by: Jonathan Peppers <[email protected]> --------- Co-authored-by: Jonathan Peppers <[email protected]>
dotnet · Jun 24, 2024 · 27a83b7 · 27a83b7
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diff --git a/docs/design/FeatureSwitches.md b/docs/design/FeatureSwitches.md
@@ -10,6 +10,7 @@ The following switches are toggled for applications running on Mono for `TrimMod
 | MauiShellSearchResultsRendererDisplayMemberNameSupported | Microsoft.Maui.RuntimeFeature.IsShellSearchResultsRendererDisplayMemberNameSupported | When disabled, it is necessary to always set `ItemTemplate` of any `SearchHandler`. Displaying search results through `DisplayMemberName` will not work. |
 | MauiQueryPropertyAttributeSupport | Microsoft.Maui.RuntimeFeature.IsQueryPropertyAttributeSupported | When disabled, the `[QueryProperty(...)]` attributes won't be used to set values to properties when navigating. |
 | MauiImplicitCastOperatorsUsageViaReflectionSupport | Microsoft.Maui.RuntimeFeature.IsImplicitCastOperatorsUsageViaReflectionSupported | When disabled, MAUI won't look for implicit cast operators when converting values from one type to another. This feature is not trim-compatible. |
+| _MauiBindingInterceptorsSupport | Microsoft.Maui.RuntimeFeature.AreBindingInterceptorsSupported | When disabled, MAUI won't intercept any calls to `SetBinding` methods and try to compile them. Enabled by default. |
 
 ## MauiEnableIVisualAssemblyScanning
 
@@ -32,3 +33,31 @@ When disabled, MAUI won't look for implicit cast operators when converting value
 If your library or your app defines an implicit operator on a type that can be used in one of the previous scenarios, you should define a custom `TypeConverter` for your type and attach it to the type using the `[TypeConverter(typeof(MyTypeConverter))]` attribute.
 
 _Note: Prefer using the `TypeConverterAttribute` as it can help the trimmer achieve better binary size in certain scenarios._
+
+## _MauiBindingInterceptorsSupport
+
+When enabled, MAUI will enable a source generator which will identify calls to the `SetBinding<TSource, TProperty>(this BindableObject target, BindableProperty property, Func<TSource, TProperty> getter, ...)` methods and generate optimized bindings based on the lambda expression passed as the `getter` parameter.
+
+This feature is a counterpart of [XAML Compiled bindings](https://learn.microsoft.com/dotnet/maui/fundamentals/data-binding/compiled-bindings).
+
+It is necessary to use this feature instead of the string-based bindings in NativeAOT apps and in apps with full trimming enabled.
+
+### Example use-case
+
+String-based binding in code:
+```c#
+label.BindingContext = new PageViewModel { Customer = new CustomerViewModel { Name = "John" } };
+label.SetBinding(Label.TextProperty, "Customer.Name");
+```
+
+Compiled binding in code:
+```csharp
+label.SetBinding<PageViewModel, string>(Label.TextProperty, static vm => vm.Customer.Name);
+// or with type inference:
+label.SetBinding(Label.TextProperty, static (PageViewModel vm) => vm.Customer.Name);
+```
+
+Compiled binding in XAML:
+```xml
+<Label Text="{Binding Customer.Name}" x:DataType="local:PageViewModel" />
+```
diff --git a/src/Controls/src/BindingSourceGen/BindingSourceGenerator.cs b/src/Controls/src/BindingSourceGen/BindingSourceGenerator.cs
@@ -68,7 +68,7 @@ private static Result<SetBindingInvocationDescription> GetBindingForGeneration(G
 			return Result<SetBindingInvocationDescription>.Failure(DiagnosticsFactory.UnableToResolvePath(invocation.GetLocation()));
 		}
 
-		var overloadDiagnostics = VerifyCorrectOverload(invocation, context, t);
+		var overloadDiagnostics = new EquatableArray<DiagnosticInfo>(VerifyCorrectOverload(invocation, context, t));
 		if (overloadDiagnostics.Length > 0)
 		{
 			return Result<SetBindingInvocationDescription>.Failure(overloadDiagnostics);
@@ -121,31 +121,26 @@ private static bool IsNullableContextEnabled(GeneratorSyntaxContext context)
 		return (nullableContext & NullableContext.Enabled) == NullableContext.Enabled;
 	}
 
-	private static EquatableArray<DiagnosticInfo> VerifyCorrectOverload(InvocationExpressionSyntax invocation, GeneratorSyntaxContext context, CancellationToken t)
+	private static DiagnosticInfo[] VerifyCorrectOverload(InvocationExpressionSyntax invocation, GeneratorSyntaxContext context, CancellationToken t)
 	{
 		var argumentList = invocation.ArgumentList.Arguments;
-
 		if (argumentList.Count < 2)
 		{
 			throw new ArgumentOutOfRangeException(nameof(invocation));
 		}
 
 		var secondArgument = argumentList[1].Expression;
-
-		if (secondArgument is IdentifierNameSyntax)
+		if (secondArgument is LambdaExpressionSyntax)
 		{
-			var type = context.SemanticModel.GetTypeInfo(secondArgument, cancellationToken: t).Type;
-			if (type != null && type.Name == "Func")
-			{
-				return new EquatableArray<DiagnosticInfo>([DiagnosticsFactory.GetterIsNotLambda(secondArgument.GetLocation())]);
-			}
-			else // String and Binding
-			{
-				return new EquatableArray<DiagnosticInfo>([DiagnosticsFactory.SuboptimalSetBindingOverload(secondArgument.GetLocation())]);
-			}
+			return [];
 		}
 
-		return [];
+		var secondArgumentType = context.SemanticModel.GetTypeInfo(secondArgument, cancellationToken: t).Type;
+		return secondArgumentType switch
+		{
+			{ Name: "Func", ContainingNamespace.Name: "System" } => [DiagnosticsFactory.GetterIsNotLambda(secondArgument.GetLocation())],
+			_ => [DiagnosticsFactory.SuboptimalSetBindingOverload(secondArgument.GetLocation())],
+		};
 	}
 
 	private static Result<LambdaExpressionSyntax> ExtractLambda(InvocationExpressionSyntax invocation)

diff --git a/src/Controls/src/Build.Tasks/Controls.Build.Tasks.csproj b/src/Controls/src/Build.Tasks/Controls.Build.Tasks.csproj
@@ -35,6 +35,7 @@
 		<ProjectReference Include="..\Core\Controls.Core.csproj" />
 		<ProjectReference Include="..\Xaml\Controls.Xaml.csproj" />
 		<ProjectReference Include="..\SourceGen\Controls.SourceGen.csproj" ReferenceOutputAssembly="false" />
+		<ProjectReference Include="..\BindingSourceGen\Controls.BindingSourceGen.csproj" ReferenceOutputAssembly="false" />
 	</ItemGroup>
 
 	<ItemGroup>
@@ -49,6 +50,8 @@
 		<None Include="$(PkgSystem_CodeDom)\lib\netstandard2.0\System.CodeDom.dll" Visible="false" Pack="true" PackagePath="buildTransitive\netstandard2.0" />
 		<None Include="$(ArtifactsBinDir)Controls.SourceGen\$(Configuration)\netstandard2.0\Microsoft.Maui.Controls.SourceGen.dll" Visible="false" Pack="true" PackagePath="buildTransitive\netstandard2.0" />
 		<None Include="$(ArtifactsBinDir)Controls.SourceGen\$(Configuration)\netstandard2.0\Microsoft.Maui.Controls.SourceGen.pdb" Visible="false" Pack="true" PackagePath="buildTransitive\netstandard2.0" />
+		<None Include="$(ArtifactsBinDir)Controls.BindingSourceGen\$(Configuration)\netstandard2.0\Microsoft.Maui.Controls.BindingSourceGen.dll" Visible="false" Pack="true" PackagePath="buildTransitive\netstandard2.0" />
+		<None Include="$(ArtifactsBinDir)Controls.BindingSourceGen\$(Configuration)\netstandard2.0\Microsoft.Maui.Controls.BindingSourceGen.pdb" Visible="false" Pack="true" PackagePath="buildTransitive\netstandard2.0" />
 		<None Remove="$(OutputPath)*.xml" />
 		<None Include="nuget\**" PackagePath="" Pack="true" Exclude="nuget\**\*.aotprofile.txt" />
 	</ItemGroup>

diff --git a/...rols/src/Build.Tasks/nuget/buildTransitive/netstandard2.0/Microsoft.Maui.Controls.targets b/...rols/src/Build.Tasks/nuget/buildTransitive/netstandard2.0/Microsoft.Maui.Controls.targets
@@ -21,6 +21,15 @@
 		<Analyzer Include="$(MSBuildThisFileDirectory)Microsoft.Maui.Controls.SourceGen.dll" IsImplicitlyDefined="true" />
 	</ItemGroup>
 
+	<!-- Enable BindingSourceGen -->
+	<PropertyGroup>
+		<_MauiBindingInterceptorsSupport Condition=" '$(_MauiBindingInterceptorsSupport)' == '' and '$(DisableMauiAnalyzers)' != 'true' ">true</_MauiBindingInterceptorsSupport>
+		<InterceptorsPreviewNamespaces Condition=" '$(_MauiBindingInterceptorsSupport)' == 'true' ">$(InterceptorsPreviewNamespaces);Microsoft.Maui.Controls.Generated</InterceptorsPreviewNamespaces>
+	</PropertyGroup>
+	<ItemGroup Condition=" '$(_MauiBindingInterceptorsSupport)' == 'true' ">
+		<Analyzer Include="$(MSBuildThisFileDirectory)Microsoft.Maui.Controls.BindingSourceGen.dll" IsImplicitlyDefined="true" />
+	</ItemGroup>
+
 	<ItemGroup Condition="'$(AndroidEnableProfiledAot)' == 'true' and '$(MauiUseDefaultAotProfile)' != 'false'">
 		<AndroidAotProfile Include="$(MSBuildThisFileDirectory)maui.aotprofile" />
 		<AndroidAotProfile Include="$(MSBuildThisFileDirectory)maui-blazor.aotprofile" />
@@ -242,6 +251,10 @@
                                       Condition="'$(MauiImplicitCastOperatorsUsageViaReflectionSupport)' != ''"
                                       Value="$(MauiImplicitCastOperatorsUsageViaReflectionSupport)"
                                       Trim="true" />
+      <RuntimeHostConfigurationOption Include="Microsoft.Maui.RuntimeFeature.Microsoft.Maui.RuntimeFeature.AreBindingInterceptorsSupported"
+                                      Condition="'$(_MauiBindingInterceptorsSupport)' != ''"
+                                      Value="$(_MauiBindingInterceptorsSupport)"
+                                      Trim="true" />
     </ItemGroup>
   </Target>
 

diff --git a/src/Controls/src/Core/BindableObjectExtensions.cs b/src/Controls/src/Core/BindableObjectExtensions.cs
@@ -139,6 +139,11 @@ public static void SetBinding<TSource, TProperty>(
 			object? fallbackValue = null,
 			object? targetNullValue = null)
 		{
+			if (!RuntimeFeature.AreBindingInterceptorsSupported)
+			{
+				throw new InvalidOperationException($"Call to SetBinding<{typeof(TSource)}, {typeof(TProperty)}> could not be intercepted because the feature has been disabled. Consider removing the DisableMauiAnalyzers property from your project file or set the _MauiBindingInterceptorsSupport property to true instead.");
+			}
+
 			throw new InvalidOperationException($"Call to SetBinding<{typeof(TSource)}, {typeof(TProperty)}> was not intercepted.");
 		}
 #nullable disable

diff --git a/src/Controls/tests/BindingSourceGen.UnitTests/DiagnosticsTests.cs b/src/Controls/tests/BindingSourceGen.UnitTests/DiagnosticsTests.cs
@@ -97,6 +97,40 @@ public void DoesNotReportWarningWhenUsingOverloadWithStringVariablePath()
 		Assert.Empty(result.SourceGeneratorDiagnostics);
 	}
 
+	[Fact]
+	public void DoesNotReportWarningWhenUsingOverloadWithNameofInPath()
+	{
+		var source = """
+            using Microsoft.Maui.Controls;
+            var label = new Label();
+            var slider = new Slider();
+
+            label.BindingContext = slider;
+            label.SetBinding(Label.ScaleProperty, nameof(Slider.Value));
+            """;
+
+		var result = SourceGenHelpers.Run(source);
+		Assert.Empty(result.SourceGeneratorDiagnostics);
+	}
+
+	[Fact]
+	public void DoesNotReportWarningWhenUsingOverloadWithMethodCallThatReturnsString()
+	{
+		var source = """
+            using Microsoft.Maui.Controls;
+            var label = new Label();
+            var slider = new Slider();
+
+            label.BindingContext = slider;
+            label.SetBinding(Label.ScaleProperty, GetPath());
+
+            static string GetPath() => "Value";
+            """;
+
+		var result = SourceGenHelpers.Run(source);
+		Assert.Empty(result.SourceGeneratorDiagnostics);
+	}
+
 	[Fact]
 	public void ReportsUnableToResolvePathWhenUsingMethodCall()
 	{

diff --git a/src/Core/src/RuntimeFeature.cs b/src/Core/src/RuntimeFeature.cs
@@ -18,6 +18,7 @@ internal static class RuntimeFeature
 		private const bool IsShellSearchResultsRendererDisplayMemberNameSupportedByDefault = true;
 		private const bool IsQueryPropertyAttributeSupportedByDefault = true;
 		private const bool IsImplicitCastOperatorsUsageViaReflectionSupportedByDefault = true;
+		private const bool AreBindingInterceptorsSupportedByDefault = true;
 
 #pragma warning disable IL4000 // Return value does not match FeatureGuardAttribute 'System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute'. 
 #if !NETSTANDARD
@@ -55,6 +56,11 @@ internal static bool IsShellSearchResultsRendererDisplayMemberNameSupported
 			AppContext.TryGetSwitch("Microsoft.Maui.RuntimeFeature.IsImplicitCastOperatorsUsageViaReflectionSupported", out bool isSupported)
 				? isSupported
 				: IsImplicitCastOperatorsUsageViaReflectionSupportedByDefault;
+
+		internal static bool AreBindingInterceptorsSupported =>
+			AppContext.TryGetSwitch("Microsoft.Maui.RuntimeFeature.AreBindingInterceptorsSupported", out bool areSupported)
+				? areSupported
+				: AreBindingInterceptorsSupportedByDefault;
 #pragma warning restore IL4000
 	}
 }