Add compile-time property initializer for default values in BindableProperty source generaor

.github/instructions/codestyle.instructions.md

@@ -566,3 +566,16 @@ Within a class, struct, or interface, elements should be positioned in the follo
 11. Records
 12. Structs
 13. Classes
+
+### Try Pattern
+
+When a method name begins with `Try` and returns a variable, ensure it adheres to the Try Pattern.
+
+Here Key Components of the Try Pattern:
+1. Method Name: Begins with Try (e.g., TryParse, TryGetValue).
+2. Return Type: bool (indicating success or failure).
+3. Out Parameter: An out parameter to return the result if successful.
+4. Null Analysis Attribute: [NotNullWhen(true)] (or [MaybeNullWhen(false)]) informs the compiler that if the method returns true, the out parameter is guaranteed to be non-null. 
+
+This pattern allows for high-performance retrieval or parsing without throwing exceptions for expected failures. It also allows cleaner call sites by eliminating the need for null-checking the output variable within the if block, as seen in Dictionary<TKey, TValue>.TryGetValue. 
+```

src/CommunityToolkit.Maui.SourceGenerators.UnitTests/BindablePropertyAttributeSourceGeneratorTests/BindablePropertyAttributeSourceGenerator_CommonUsageTests.cs

@@ -598,8 +598,8 @@ public partial class {{defaultTestClassName}}
 			    /// <summary>
 			    /// BindableProperty for the <see cref = "Text"/> property.
 			    /// </summary>
-			    public static readonly global::Microsoft.Maui.Controls.BindableProperty TextProperty = global::Microsoft.Maui.Controls.BindableProperty.Create("Text", typeof(string), typeof({{defaultTestNamespace}}.{{defaultTestClassName}}), null, (Microsoft.Maui.Controls.BindingMode)0, null, null, null, null, __{{defaultTestClassName}}BindablePropertyInitHelpers.CreateDefaultText);
-			    public partial string Text { get => __{{defaultTestClassName}}BindablePropertyInitHelpers.IsInitializingText ? field : (string)GetValue(TextProperty); set => SetValue(TextProperty, value); }
+			    public static readonly global::Microsoft.Maui.Controls.BindableProperty TextProperty = global::Microsoft.Maui.Controls.BindableProperty.Create("Text", typeof(string), typeof({{defaultTestNamespace}}.{{defaultTestClassName}}), "Initial Value", (Microsoft.Maui.Controls.BindingMode)0, null, null, null, null, null);
+			    public partial string Text { get => false ? field : (string)GetValue(TextProperty); set => SetValue(TextProperty, value); }
 
 			    /// <summary>
 			    /// BindableProperty for the <see cref = "CustomDuration"/> property.
@@ -610,20 +610,11 @@ public partial class {{defaultTestClassName}}
 
 			file static class __{{defaultTestClassName}}BindablePropertyInitHelpers
 			{
-			    public static volatile bool IsInitializingText = false;
-			    public static object CreateDefaultText(global::Microsoft.Maui.Controls.BindableObject bindable)
-			    {
-			        IsInitializingText = true;
-			        var defaultValue = ((TestView)bindable).Text;
-			        IsInitializingText = false;
-			        return defaultValue;
-			    }
-
 			    public static volatile bool IsInitializingCustomDuration = false;
 			    public static object CreateDefaultCustomDuration(global::Microsoft.Maui.Controls.BindableObject bindable)
 			    {
 			        IsInitializingCustomDuration = true;
-			        var defaultValue = ((TestView)bindable).CustomDuration;
+			        var defaultValue = (({{defaultTestClassName}})bindable).CustomDuration;
 			        IsInitializingCustomDuration = false;
 			        return defaultValue;
 			    }

src/CommunityToolkit.Maui.SourceGenerators.UnitTests/BindablePropertyAttributeSourceGeneratorTests/BindablePropertyAttributeSourceGenerator_IntegrationTests.cs

@@ -162,21 +162,8 @@ public partial class {{defaultTestClassName}}<T, U>
 		    /// <summary>
 		    /// BindableProperty for the <see cref = "Value"/> property.
 		    /// </summary>
-		    public static readonly global::Microsoft.Maui.Controls.BindableProperty ValueProperty = global::Microsoft.Maui.Controls.BindableProperty.Create("Value", typeof(T), typeof({{defaultTestNamespace}}.{{defaultTestClassName}}<T, U>), null, (Microsoft.Maui.Controls.BindingMode)0, null, null, null, null, __{{defaultTestClassName}}BindablePropertyInitHelpers.CreateDefaultValue);
-		    public partial T? Value { get => __{{defaultTestClassName}}BindablePropertyInitHelpers.IsInitializingValue ? field : (T? )GetValue(ValueProperty); set => SetValue(ValueProperty, value); }
-
-		    [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
-		    private static class __{{defaultTestClassName}}BindablePropertyInitHelpers
-		    {
-		        public static volatile bool IsInitializingValue = false;
-		        public static object CreateDefaultValue(global::Microsoft.Maui.Controls.BindableObject bindable)
-		        {
-		            IsInitializingValue = true;
-		            var defaultValue = (({{defaultTestClassName}}<T, U>)bindable).Value;
-		            IsInitializingValue = false;
-		            return defaultValue;
-		        }
-		    }
+		    public static readonly global::Microsoft.Maui.Controls.BindableProperty ValueProperty = global::Microsoft.Maui.Controls.BindableProperty.Create("Value", typeof(T), typeof({{defaultTestNamespace}}.{{defaultTestClassName}}<T, U>), default(T), (Microsoft.Maui.Controls.BindingMode)0, null, null, null, null, null);
+		    public partial T? Value { get => false ? field : (T? )GetValue(ValueProperty); set => SetValue(ValueProperty, value); }
 		}
 		""";
 

src/CommunityToolkit.Maui.SourceGenerators.UnitTests/BindablePropertyModelTests.cs

@@ -30,7 +30,8 @@ public void BindablePropertyName_ReturnsCorrectPropertyName()
 			true, // IsReadOnlyBindableProperty
 			string.Empty, // SetterAccessibility
 			false,
-			"null"
+			"null",
+			null
 		);
 
 		// Act
@@ -74,7 +75,8 @@ public void BindablePropertyModel_WithAllParameters_StoresCorrectValues()
 			true, // IsReadOnlyBindableProperty
 			string.Empty, // SetterAccessibility
 			hasInitializer,
-			propertyAccessibility
+			propertyAccessibility,
+			null
 		);
 
 		// Assert
@@ -135,7 +137,8 @@ public void SemanticValues_WithClassInfoAndProperties_StoresCorrectValues()
 			true, // IsReadOnlyBindableProperty
 			string.Empty, // SetterAccessibilityText
 			false,
-			"public"
+			"public",
+			null
 		);
 
 		var bindableProperties = new[] { bindableProperty }.ToImmutableArray();
@@ -194,7 +197,8 @@ public class TestClass { public string TestProperty { get; set; } = "Initial Val
 			true,
 			string.Empty,
 			hasInitializer,
-			"public"
+			"public",
+			null
 		);
 
 		// Act
@@ -234,7 +238,8 @@ public class TestClass { public string TestProperty { get; set; } = "Initial Val
 			true,
 			string.Empty,
 			hasInitializer,
-			"public"
+			"public",
+			null
 		);
 
 		// Act

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

@@ -237,7 +237,9 @@ static void GenerateReadOnlyBindableProperty(StringBuilder sb, in BindableProper
 			.Append(GetFormattedReturnType(nonNullableReturnType))
 			.Append("), typeof(")
 			.Append(info.DeclaringType)
-			.Append("), null, ")
+			.Append("), ")
+			.Append(info.ResolvedInitializerExpression ?? "null")
+			.Append(", ")
 			.Append(info.DefaultBindingMode)
 			.Append(", ")
 			.Append(info.ValidateValueMethodName)
@@ -304,7 +306,9 @@ static void GenerateBindableProperty(StringBuilder sb, in BindablePropertyModel
 			.Append(GetFormattedReturnType(nonNullableReturnType))
 			.Append("), typeof(")
 			.Append(info.DeclaringType)
-			.Append("), null, ")
+			.Append("), ")
+			.Append(info.ResolvedInitializerExpression ?? "null")
+			.Append(", ")
 			.Append(info.DefaultBindingMode)
 			.Append(", ")
 			.Append(info.ValidateValueMethodName)
@@ -408,8 +412,15 @@ static BindablePropertySemanticValues SemanticTransform(GeneratorAttributeSyntax
 
 		var propertyAccessibility = GetPropertyAccessibility(propertySymbol);
 
+		// Resolve initializer expression to a fully qualified string for use as defaultValue
+		string? resolvedInitializer = null;
+		if (hasInitializer && propertyDeclarationSyntax.Initializer is not null)
+		{
+			InitializerExpressionResolver.TryResolve(propertyDeclarationSyntax.Initializer.Value, semanticModel, out resolvedInitializer);
+		}
+
 		var attributeData = context.Attributes[0];
-		bindablePropertyModels[0] = CreateBindablePropertyModel(attributeData, propertySymbol.ContainingType, propertySymbol.Name, returnType, doesContainNewKeyword, isReadOnlyBindableProperty, setterAccessibility, hasInitializer, propertyAccessibility);
+		bindablePropertyModels[0] = CreateBindablePropertyModel(attributeData, propertySymbol.ContainingType, propertySymbol.Name, returnType, doesContainNewKeyword, isReadOnlyBindableProperty, setterAccessibility, hasInitializer, propertyAccessibility, resolvedInitializer);
 
 		return new(propertyInfo, ImmutableArray.Create(bindablePropertyModels));
 	}
@@ -517,7 +528,7 @@ static string GetGenericTypeParameters(INamedTypeSymbol typeSymbol)
 		return sb.ToString();
 	}
 
-	static BindablePropertyModel CreateBindablePropertyModel(in AttributeData attributeData, in INamedTypeSymbol declaringType, in string propertyName, in ITypeSymbol returnType, in bool doesContainNewKeyword, in bool isReadOnly, in string? setterAccessibility, in bool hasInitializer, in string? propertyAccessibility)
+	static BindablePropertyModel CreateBindablePropertyModel(in AttributeData attributeData, in INamedTypeSymbol declaringType, in string propertyName, in ITypeSymbol returnType, in bool doesContainNewKeyword, in bool isReadOnly, in string? setterAccessibility, in bool hasInitializer, in string? propertyAccessibility, in string? resolvedInitializerExpression)
 	{
 		if (attributeData.AttributeClass is null)
 		{
@@ -532,7 +543,10 @@ static BindablePropertyModel CreateBindablePropertyModel(in AttributeData attrib
 		var validateValueMethodName = attributeData.GetNamedMethodGroupArgumentsAttributeValueByNameAsString(nameof(BindablePropertyModel.ValidateValueMethodName));
 		var newKeywordText = doesContainNewKeyword ? "new " : string.Empty;
 
-		return new BindablePropertyModel(propertyName, returnType, declaringType, defaultBindingMode, validateValueMethodName, propertyChangedMethodName, propertyChangingMethodName, coerceValueMethodName, defaultValueCreatorMethodName, newKeywordText, isReadOnly, setterAccessibility, hasInitializer, propertyAccessibility);
+		// Only use the resolved initializer when there's no explicit DefaultValueCreatorMethodName
+		var effectiveResolvedInitializer = defaultValueCreatorMethodName is "null" ? resolvedInitializerExpression : null;
+
+		return new BindablePropertyModel(propertyName, returnType, declaringType, defaultBindingMode, validateValueMethodName, propertyChangedMethodName, propertyChangingMethodName, coerceValueMethodName, defaultValueCreatorMethodName, newKeywordText, isReadOnly, setterAccessibility, hasInitializer, propertyAccessibility, effectiveResolvedInitializer);
 	}
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]