Update BindablePropertySourceGenerator to use partial properties

src/CommunityToolkit.Maui.SourceGenerators.Internal/BindablePropertyAttributeSourceGenerator.cs

@@ -1,4 +1,5 @@
 using System.Collections.Immutable;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using System.Text;
 using CommunityToolkit.Maui.SourceGenerators.Helpers;
@@ -21,15 +22,19 @@ public class BindablePropertyAttributeSourceGenerator : IIncrementalGenerator
 	const string bpAttribute =
 		/* language=C#-test */
 		//lang=csharp
-		"""
+		$$"""
+		// <auto-generated>
+		// See: CommunityToolkit.Maui.SourceGenerators.Internal.BindablePropertyAttributeSourceGenerator
+
 		#pragma warning disable
 		#nullable enable
 		namespace CommunityToolkit.Maui;
 
-		[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
-		sealed partial class BindablePropertyAttribute<TReturnType> : Attribute
+		[global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+		[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
+		sealed partial class BindablePropertyAttribute : Attribute
 		{
-			public string PropertyName { get; } = string.Empty;
+			public string? PropertyName { get; }
 			public Type? DeclaringType { get; set; }
 			public object? DefaultValue { get; set; }
 			public string DefaultBindingMode { get; set; } = string.Empty;
@@ -43,30 +48,67 @@ public BindablePropertyAttribute(string propertyName)
 			{
 				PropertyName = propertyName;
 			}
+
+			public BindablePropertyAttribute()
+			{
+			}
 		}
 		""";
 
 	public void Initialize(IncrementalGeneratorInitializationContext context)
 	{
-		context.RegisterPostInitializationOutput(ctx => ctx.AddSource("BindablePropertyAttribute.g.cs", SourceText.From(bpAttribute, Encoding.UTF8)));
 
-		var provider = context.SyntaxProvider.ForAttributeWithMetadataName("CommunityToolkit.Maui.BindablePropertyAttribute`1",
+#if DEBUG
+
+		if (!Debugger.IsAttached)
+		{
+			// To debug this SG, uncomment the line below and rebuild the SourceGenerator project.
+
+			//Debugger.Launch();
+		}
+#endif
+
+		context.RegisterPostInitializationOutput(static ctx => ctx.AddSource("BindablePropertyAttribute.g.cs", SourceText.From(bpAttribute, Encoding.UTF8)));
+
+		var provider = context.SyntaxProvider.ForAttributeWithMetadataName("CommunityToolkit.Maui.BindablePropertyAttribute",
 				SyntaxPredicate, SemanticTransform)
 			.Where(static x => x.ClassInformation != default || !x.BindableProperties.IsEmpty)
-			.Collect()
-			.SelectMany(static (types, _) => types);
+			.Collect();
 
 
-		context.RegisterSourceOutput(provider, Execute);
+		context.RegisterSourceOutput(provider, ExecuteAllValues);
 	}
 
-	static void Execute(SourceProductionContext context, SemanticValues semanticValues)
+	static void ExecuteAllValues(SourceProductionContext context, ImmutableArray<SemanticValues> semanticValues)
 	{
-		var source = GenerateSource(semanticValues);
-		SourceStringService.FormatText(ref source);
-		context.AddSource($"{semanticValues.ClassInformation.ClassName}.g.cs", SourceText.From(source, Encoding.UTF8));
+		var groupedValues = semanticValues
+		.GroupBy(static sv => (sv.ClassInformation.ClassName, sv.ClassInformation.ContainingNamespace))
+		.ToDictionary(static d => d.Key, static d => d.ToArray());
+
+		foreach (var keyValuePair in groupedValues)
+		{
+			var (className, containingNamespace) = keyValuePair.Key;
+			var values = keyValuePair.Value;
+
+			if (values.Length is 0 || string.IsNullOrEmpty(className) || string.IsNullOrEmpty(containingNamespace))
+			{
+				continue;
+			}
+
+			var bindableProperties = values.SelectMany(static x => x.BindableProperties).ToImmutableArray();
+
+			var classAccessibility = values[0].ClassInformation.DeclaredAccessibility;
+
+			var combinedClassInfo = new ClassInformation(className, classAccessibility, containingNamespace);
+			var combinedValues = new SemanticValues(combinedClassInfo, bindableProperties);
+
+			var source = GenerateSource(combinedValues);
+			SourceStringService.FormatText(ref source);
+			context.AddSource($"{className}.g.cs", SourceText.From(source, Encoding.UTF8));
+		}
 	}
 
+
 	static string GenerateSource(SemanticValues value)
 	{
 		var sb = new StringBuilder(
@@ -124,17 +166,16 @@ static void GenerateBindableProperty(StringBuilder sb, BindablePropertyModel inf
 
 		static void GenerateProperty(StringBuilder sb, BindablePropertyModel info)
 		{
-			/*
-			/// <inheritdoc />
-			*/
-			sb.AppendLine("/// <inheritdoc />");
-
-			//public string Text
-			//{
-			//	get => (string)GetValue(TextProperty);
-			//	set => SetValue(TextProperty, value);
-			//}
-			sb.AppendLine($"public {info.ReturnType} {info.PropertyName}")
+			// The code below creates the following Property:
+			//
+			//	public partial string Text
+			//	{
+			//		get => (string)GetValue(TextProperty);
+			//		set => SetValue(TextProperty, value);
+			//	}
+			//
+
+			sb.AppendLine($"public partial {info.ReturnType} {info.PropertyName}")
 				.AppendLine("{")
 				.Append("get => (")
 				.Append(info.ReturnType)
@@ -148,45 +189,45 @@ static void GenerateProperty(StringBuilder sb, BindablePropertyModel info)
 
 	static SemanticValues SemanticTransform(GeneratorAttributeSyntaxContext context, CancellationToken cancellationToken)
 	{
-		var classDeclarationSyntax = Unsafe.As<ClassDeclarationSyntax>(context.TargetNode);
+		var propertyDeclarationSyntax = Unsafe.As<PropertyDeclarationSyntax>(context.TargetNode);
 		var semanticModel = context.SemanticModel;
-		var classSymbol = (ITypeSymbol?)semanticModel.GetDeclaredSymbol(classDeclarationSyntax, cancellationToken);
+		var propertySymbol = (IPropertySymbol?)semanticModel.GetDeclaredSymbol(propertyDeclarationSyntax, cancellationToken);
 
-		if (classSymbol is null)
+		if (propertySymbol is null)
 		{
 			return emptySemanticValues;
 		}
 
-		var classInfo = new ClassInformation(classSymbol.Name, classSymbol.DeclaredAccessibility.ToString().ToLower(), classSymbol.ContainingNamespace.ToDisplayString());
+		var @namespace = propertySymbol.ContainingNamespace.ToDisplayString();
+		var className = propertySymbol.ContainingType.Name;
+		var classAccessibility = propertySymbol.ContainingSymbol.DeclaredAccessibility.ToString().ToLower();
+		var returnType = propertySymbol.Type;
 
+		var propertyInfo = new ClassInformation(className, classAccessibility, @namespace);
 
 		var bindablePropertyModels = new List<BindablePropertyModel>(context.Attributes.Length);
 
-		for (var index = 0; index < context.Attributes.Length; index++)
-		{
-			var attributeData = context.Attributes[index];
-			bindablePropertyModels.Add(GetAttributeValues(attributeData, classSymbol?.ToString() ?? string.Empty));
-		}
+		var attributeData = context.Attributes[0];
+		bindablePropertyModels.Add(CreateBindablePropertyModel(attributeData, propertySymbol.Type.ToDisplayString(), propertySymbol.Name, returnType));
 
-		return new(classInfo, bindablePropertyModels.ToImmutableArray());
+		return new(propertyInfo, bindablePropertyModels.ToImmutableArray());
 	}
 
-	static BindablePropertyModel GetAttributeValues(in AttributeData attributeData, in string declaringTypeString)
+	static BindablePropertyModel CreateBindablePropertyModel(in AttributeData attributeData, in string declaringTypeString, in string defaultName, in ITypeSymbol returnType)
 	{
 		if (attributeData.AttributeClass is null)
 		{
 			throw new ArgumentException($"{nameof(attributeData.AttributeClass)} Cannot Be Null", nameof(attributeData.AttributeClass));
 		}
 
-		var bpType = attributeData.AttributeClass.TypeArguments[0];
 		var defaultValue = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.DefaultValue));
 		var coerceValueMethodName = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.CoerceValueMethodName));
 		var defaultBindingMode = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.DefaultBindingMode), "BindingMode.OneWay");
 		var defaultValueCreatorMethodName = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.DefaultValueCreatorMethodName));
 		var declaringType = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.DeclaringType), declaringTypeString);
 		var propertyChangedMethodName = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.PropertyChangedMethodName));
 		var propertyChangingMethodName = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.PropertyChangingMethodName));
-		var propertyName = attributeData.GetConstructorArgumentsAttributeValueByNameAsString();
+		var propertyName = attributeData.GetConstructorArgumentsAttributeValueByNameAsString(defaultName);
 		var validateValueMethodName = attributeData.GetNamedArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.ValidateValueMethodName));
 
 		return new BindablePropertyModel
@@ -199,11 +240,11 @@ static BindablePropertyModel GetAttributeValues(in AttributeData attributeData,
 			PropertyChangedMethodName = propertyChangedMethodName,
 			PropertyChangingMethodName = propertyChangingMethodName,
 			PropertyName = propertyName,
-			ReturnType = bpType,
+			ReturnType = returnType,
 			ValidateValueMethodName = validateValueMethodName
 		};
 	}
 
 	static bool SyntaxPredicate(SyntaxNode node, CancellationToken cancellationToken) =>
-		node is ClassDeclarationSyntax { AttributeLists.Count: > 0 };
+		node is PropertyDeclarationSyntax { AttributeLists.Count: > 0 };
 }

src/CommunityToolkit.Maui.SourceGenerators.Internal/Helpers/AttributeExtensions.cs

@@ -17,11 +17,16 @@ public static string GetNamedArgumentsAttributeValueByNameAsString(this Attribut
 		return data.Value is null ? placeholder : data.Value.ToString();
 	}
 
-	public static string GetConstructorArgumentsAttributeValueByNameAsString(this AttributeData attribute)
+	public static string GetConstructorArgumentsAttributeValueByNameAsString(this AttributeData attribute, string placeholder)
 	{
+		if (attribute.ConstructorArguments.Length is 0)
+		{
+			return placeholder;
+		}
+
 		var data = attribute.ConstructorArguments[0];
 
-		return data.Value is null ? throw new InvalidOperationException() : data.Value.ToString();
+		return data.Value is null ? placeholder : data.Value.ToString();
 	}
 
 }

src/CommunityToolkit.Maui/Views/Expander/Expander.shared.cs

@@ -6,16 +6,41 @@
 namespace CommunityToolkit.Maui.Views;
 
 /// <inheritdoc cref="IExpander"/>
-[BindableProperty<IView>("Header", PropertyChangedMethodName = nameof(OnHeaderPropertyChanged))]
-[BindableProperty<IView>("Content", PropertyChangedMethodName = nameof(OnContentPropertyChanged))]
-[BindableProperty<bool>("IsExpanded", PropertyChangedMethodName = nameof(OnIsExpandedPropertyChanged))]
-[BindableProperty<object>("CommandParameter")]
-[BindableProperty<ICommand>("Command")]
 [ContentProperty(nameof(Content))]
 [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
 [RequiresUnreferencedCode("Calls Microsoft.Maui.Controls.Binding.Binding(String, BindingMode, IValueConverter, Object, String, Object)")]
 public partial class Expander : ContentView, IExpander
 {
+	/// <summary>
+	/// Gets or sets the command to execute when the expander is expanded or collapsed.
+	/// </summary>
+	[BindableProperty]
+	public partial ICommand Command { get; set; }
+
+	/// <summary>
+	/// Gets or sets the parameter to pass to the <see cref="Command"/> property.
+	/// </summary>
+	[BindableProperty]
+	public partial object CommandParameter { get; set; }
+
+	/// <summary>
+	/// Gets or sets a value indicating whether the expander is expanded.
+	/// </summary>
+	[BindableProperty(PropertyChangedMethodName = nameof(OnIsExpandedPropertyChanged))]
+	public partial bool IsExpanded { get; set; }
+
+	/// <summary>
+	/// Gets or sets the content to be expanded or collapsed.
+	/// </summary>
+	[BindableProperty(PropertyChangedMethodName = nameof(OnContentPropertyChanged))]
+	public partial IView Content { get; set; }
+
+	/// <summary>
+	/// Gets or sets the header view of the expander.
+	/// </summary>
+	[BindableProperty(PropertyChangedMethodName = nameof(OnHeaderPropertyChanged))]
+	public partial IView Header { get; set; }
+
 	/// <summary>
 	/// Backing BindableProperty for the <see cref="Direction"/> property.
 	/// </summary>
@@ -43,7 +68,7 @@
 	}
 
 	/// <summary>
-	///	Triggered when the value of <see cref="IsExpanded"/> changes
+	/// Triggered when the value of <see cref="IsExpanded"/> changes.
 	/// </summary>
 	public event EventHandler<ExpandedChangedEventArgs> ExpandedChanged
 	{