Move out-of-scope variables to file static class

Author: TheCodeTraveler

src/CommunityToolkit.Maui.SourceGenerators.Internal.UnitTests/BindablePropertyAttributeSourceGeneratorTests/CommonUsageTests.cs

@@ -691,32 +691,35 @@ public partial class {{defaultTestClassName}}
 			    /// <summary>
 			    /// Backing 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.OneWay, null, null, null, null, __createDefaultText);
-			    bool __initializingText = false;
-			    static object __createDefaultText(global::Microsoft.Maui.Controls.BindableObject bindable)
-			    {
-			        (({{defaultTestClassName}})bindable).__initializingText = true;
-			        var defaultValue = (({{defaultTestClassName}})bindable).Text;
-			        (({{defaultTestClassName}})bindable).__initializingText = false;
-			        return defaultValue;
-			    }
-
-			    public partial string Text { get => __initializingText ? 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}}), null, Microsoft.Maui.Controls.BindingMode.OneWay, null, null, null, null, __BindablePropertyInitHelpers.CreateDefaultText);
+			    public partial string Text { get => __BindablePropertyInitHelpers.IsInitializingText ? field : (string)GetValue(TextProperty); set => SetValue(TextProperty, value); }
 
 			    /// <summary>
 			    /// Backing BindableProperty for the <see cref = "CustomDuration"/> property.
 			    /// </summary>
-			    public static readonly global::Microsoft.Maui.Controls.BindableProperty CustomDurationProperty = global::Microsoft.Maui.Controls.BindableProperty.Create("CustomDuration", typeof(System.TimeSpan), typeof({{defaultTestNamespace}}.{{defaultTestClassName}}), null, Microsoft.Maui.Controls.BindingMode.OneWay, null, null, null, null, __createDefaultCustomDuration);
-			    bool __initializingCustomDuration = false;
-			    static object __createDefaultCustomDuration(global::Microsoft.Maui.Controls.BindableObject bindable)
+			    public static readonly global::Microsoft.Maui.Controls.BindableProperty CustomDurationProperty = global::Microsoft.Maui.Controls.BindableProperty.Create("CustomDuration", typeof(System.TimeSpan), typeof({{defaultTestNamespace}}.{{defaultTestClassName}}), null, Microsoft.Maui.Controls.BindingMode.OneWay, null, null, null, null, __BindablePropertyInitHelpers.CreateDefaultCustomDuration);
+			    public partial System.TimeSpan CustomDuration { get => __BindablePropertyInitHelpers.IsInitializingCustomDuration ? field : (System.TimeSpan)GetValue(CustomDurationProperty); set => SetValue(CustomDurationProperty, value); }
+			}
+
+			file static class __BindablePropertyInitHelpers
+			{
+			    public static bool IsInitializingText = false;
+			    public static object CreateDefaultText(global::Microsoft.Maui.Controls.BindableObject bindable)
 			    {
-			        (({{defaultTestClassName}})bindable).__initializingCustomDuration = true;
-			        var defaultValue = (({{defaultTestClassName}})bindable).CustomDuration;
-			        (({{defaultTestClassName}})bindable).__initializingCustomDuration = false;
+			        IsInitializingText = true;
+			        var defaultValue = ((TestView)bindable).Text;
+			        IsInitializingText = false;
 			        return defaultValue;
 			    }
 			
-			    public partial System.TimeSpan CustomDuration { get => __initializingCustomDuration ? field : (System.TimeSpan)GetValue(CustomDurationProperty); set => SetValue(CustomDurationProperty, value); }
+			    public static bool IsInitializingCustomDuration = false;
+			    public static object CreateDefaultCustomDuration(global::Microsoft.Maui.Controls.BindableObject bindable)
+			    {
+			        IsInitializingCustomDuration = true;
+			        var defaultValue = ((TestView)bindable).CustomDuration;
+			        IsInitializingCustomDuration = false;
+			        return defaultValue;
+			    }
 			}
 			""";
 

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

@@ -92,7 +92,7 @@ public void BindablePropertyModel_WithAllParameters_StoresCorrectValues()
 		Assert.Equal(hasInitializer, model.HasInitializer);
 		Assert.Equal("TestPropertyProperty", model.BindablePropertyName);
 		Assert.Equal(defaultValueCreatorMethodName, model.EffectiveDefaultValueCreatorMethodName);
-		Assert.Equal("__initializingTestProperty", model.InitializingPropertyName);
+		Assert.Equal("IsInitializingTestProperty", model.InitializingPropertyName);
 	}
 
 	[Fact]
@@ -196,6 +196,41 @@ public void BindablePropertyName_WithInitializer_ReturnsCorrectEffectiveDefaultV
 		var effectiveDefaultValueCreatorMethodName = model.EffectiveDefaultValueCreatorMethodName;
 
 		// Assert
-		Assert.Equal("__createDefault" + propertyName, effectiveDefaultValueCreatorMethodName);
+		Assert.Equal("CreateDefault" + propertyName, effectiveDefaultValueCreatorMethodName);
+	}
+
+	[Fact]
+	public void BindablePropertyName_WithInitializerAndDefaulValueCreator_ReturnsCorrectEffectiveDefaultValueCreatorMethodName()
+	{
+		// Arrange
+		var compilation = CreateCompilation("public class TestClass { public string TestProperty { get; set; } = \"Initial Value\"; }");
+		var typeSymbol = compilation.GetTypeByMetadataName("TestClass")!;
+		var propertySymbol = typeSymbol.GetMembers("TestProperty").OfType<IPropertySymbol>().First();
+
+		const string propertyName = "TestProperty";
+		const bool hasInitializer = true;
+
+		var model = new BindablePropertyModel(
+			propertyName,
+			propertySymbol.Type,
+			typeSymbol,
+			"null",
+			"Microsoft.Maui.Controls.BindingMode.OneWay",
+			"null",
+			"null",
+			"null",
+			"null",
+			"CreateTextDefaultValue",
+			string.Empty,
+			true,
+			string.Empty,
+			hasInitializer
+		);
+
+		// Act
+		var effectiveDefaultValueCreatorMethodName = model.EffectiveDefaultValueCreatorMethodName;
+
+		// Assert
+		Assert.Equal("CreateTextDefaultValue", effectiveDefaultValueCreatorMethodName);
 	}
 }

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

@@ -174,24 +174,42 @@ static string GenerateSource(SemanticValues value)
 
 		sb.Append(value.ClassInformation.DeclaredAccessibility).Append(" partial class ").Append(classNameWithGenerics).Append("\n{\n\n");
 
+		// Prepare helper builder for file-static class members (static flags + default creators)
+		var fileStaticClassStringBuilder = new StringBuilder(256);
+		var helperNames = new HashSet<string>();
+		const string fileStaticClassName = "__BindablePropertyInitHelpers";
+
+		// Build fully-qualified declaring type name for helper method casts (include containing types)
+		var fullDeclaringType = string.IsNullOrEmpty(value.ClassInformation.ContainingTypes)
+			? classNameWithGenerics
+			: string.Concat(value.ClassInformation.ContainingTypes, ".", classNameWithGenerics);
+
 		foreach (var info in value.BindableProperties)
 		{
 			if (info.IsReadOnlyBindableProperty)
 			{
-				GenerateReadOnlyBindableProperty(sb, in info);
+				GenerateReadOnlyBindableProperty(sb, in info, fileStaticClassName);
 			}
 			else
 			{
-				GenerateBindableProperty(sb, in info);
+				GenerateBindableProperty(sb, in info, fileStaticClassName);
 			}
 
 			if (info.ShouldUsePropertyInitializer)
 			{
-				GenerateInitializingProperty(sb, in info);
-				GenerateDefaultValueMethod(sb, in info, classNameWithGenerics);
+				// Generate only references within the class; actual static field and creator method
+				// will be placed inside the file static helper class below.
+				if (helperNames.Add(info.InitializingPropertyName))
+				{
+					AppendHelperInitializingField(fileStaticClassStringBuilder, in info);
+				}
+				if (helperNames.Add(info.EffectiveDefaultValueCreatorMethodName))
+				{
+					AppendHelperDefaultValueMethod(fileStaticClassStringBuilder, in info, fullDeclaringType);
+				}
 			}
 
-			GenerateProperty(sb, in info);
+			GenerateProperty(sb, in info, fileStaticClassName);
 		}
 
 		sb.Append('}');
@@ -206,11 +224,19 @@ static string GenerateSource(SemanticValues value)
 			}
 		}
 
+		// If we generated any helper members, emit a file static class with them.
+		if (fileStaticClassStringBuilder.Length > 0)
+		{
+			sb.Append("\n\nfile static class ").Append(fileStaticClassName).Append("\n{\n");
+			sb.Append(fileStaticClassStringBuilder.ToString());
+			sb.Append("}\n");
+		}
+
 		return sb.ToString();
 	}
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	static void GenerateReadOnlyBindableProperty(StringBuilder sb, in BindablePropertyModel info)
+	static void GenerateReadOnlyBindableProperty(StringBuilder sb, in BindablePropertyModel info, in string fileStaticClassName)
 	{
 		// Sanitize the Return Type because Nullable Reference Types cannot be used in the `typeof()` operator
 		var nonNullableReturnType = ConvertToNonNullableTypeSymbol(info.ReturnType);
@@ -243,8 +269,15 @@ static void GenerateReadOnlyBindableProperty(StringBuilder sb, in BindableProper
 			.Append(info.PropertyChangingMethodName)
 			.Append(", ")
 			.Append(info.CoerceValueMethodName)
-			.Append(", ")
-			.Append(info.EffectiveDefaultValueCreatorMethodName)
+			.Append(", ");
+
+		if (info.ShouldUsePropertyInitializer)
+		{
+			sb.Append(fileStaticClassName)
+				.Append('.');
+		}
+
+		sb.Append(info.EffectiveDefaultValueCreatorMethodName)
 			.Append(");\n");
 
 		// Generate public BindableProperty from the key
@@ -262,7 +295,7 @@ static void GenerateReadOnlyBindableProperty(StringBuilder sb, in BindableProper
 	}
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	static void GenerateBindableProperty(StringBuilder sb, in BindablePropertyModel info)
+	static void GenerateBindableProperty(StringBuilder sb, in BindablePropertyModel info, in string helperClassName)
 	{
 		// Sanitize the Return Type because Nullable Reference Types cannot be used in the `typeof()` operator
 		var nonNullableReturnType = ConvertToNonNullableTypeSymbol(info.ReturnType);
@@ -299,15 +332,21 @@ static void GenerateBindableProperty(StringBuilder sb, in BindablePropertyModel
 			.Append(info.PropertyChangingMethodName)
 			.Append(", ")
 			.Append(info.CoerceValueMethodName)
-			.Append(", ")
-			.Append(info.EffectiveDefaultValueCreatorMethodName)
-			.Append(");\n");
+			.Append(", ");
 
-		sb.Append('\n');
+		if (info.ShouldUsePropertyInitializer)
+		{
+			sb.Append(helperClassName)
+			.Append('.');
+		}
+
+		sb.Append(info.EffectiveDefaultValueCreatorMethodName)
+			.Append(");\n")
+			.Append('\n');
 	}
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	static void GenerateProperty(StringBuilder sb, in BindablePropertyModel info)
+	static void GenerateProperty(StringBuilder sb, in BindablePropertyModel info, in string fileStaticClassName)
 	{
 		var sanitizedPropertyName = IsDotnetKeyword(info.PropertyName) ? string.Concat("@", info.PropertyName) : info.PropertyName;
 		var formattedReturnType = GetFormattedReturnType(info.ReturnType);
@@ -324,7 +363,8 @@ static void GenerateProperty(StringBuilder sb, in BindablePropertyModel info)
 		{
 			if (info.ShouldUsePropertyInitializer)
 			{
-				sb.Append(info.InitializingPropertyName);
+				// Now reference the static flag on the file static helper class
+				sb.Append(fileStaticClassName).Append(".").Append(info.InitializingPropertyName);
 			}
 			else
 			{
@@ -556,52 +596,44 @@ static string GetFormattedReturnType(ITypeSymbol typeSymbol)
 	}
 
 	/// <summary>
-	/// Generates the boolean initialization flag used by bindable properties with initializers to indicate that the getter
-	/// should return the backing field while the generated default value method is executing.
+	/// Appends the initializing flag into the file-static helper class.
 	/// </summary>
-	/// <param name="sb">The StringBuilder instance to which the initialization field declaration will be appended.</param>
-	/// <param name="info">The model containing metadata about the property for which the initialization field is generated.</param>
-	static void GenerateInitializingProperty(StringBuilder sb, in BindablePropertyModel info)
+	/// <param name="helperSb">Helper StringBuilder used to collect helper members.</param>
+	/// <param name="info">Property model.</param>
+	static void AppendHelperInitializingField(StringBuilder helperSb, in BindablePropertyModel info)
 	{
-		sb.Append("bool ")
+		// Make the flag public static so it can be referenced from the generated partial class in the same file.
+		helperSb.Append("public static bool ")
 			.Append(info.InitializingPropertyName)
 			.Append(" = false;\n");
 	}
 
 	/// <summary>
-	/// Generates the default value creator static method used by BindableProperty instances with initializers.
-	/// This method temporarily switches the property's getter to return its backing field while the default value is being computed,
-	/// ensuring that the initializer-provided value is captured and returned as the BindableProperty's default.
+	/// Appends a default value creator method into the file-static helper class.
+	/// The method sets the static initializing flag, reads the property's initializer value by casting the bindable
+	/// to the declaring type, then clears the flag and returns the value.
 	/// </summary>
-	/// <param name="sb">The StringBuilder instance to which the initialization field declaration will be appended.</param>
-	/// <param name="info">The model containing metadata for the property that requires a default value creator.</param>
-	/// <param name="classNameWithGenerics">The declaring class name including generic type parameters, if any.</param>
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	static void GenerateDefaultValueMethod(StringBuilder sb, in BindablePropertyModel info, string classNameWithGenerics)
+	/// <param name="helperSb">Helper StringBuilder used to collect helper members.</param>
+	/// <param name="info">Property model.</param>
+	/// <param name="fullDeclaringType">Declaring type including containing types and generic parameters.</param>
+	static void AppendHelperDefaultValueMethod(StringBuilder helperSb, in BindablePropertyModel info, string fullDeclaringType)
 	{
 		var sanitizedPropertyName = IsDotnetKeyword(info.PropertyName) ? string.Concat("@", info.PropertyName) : info.PropertyName;
 
-		sb.Append("static object ")
+		helperSb.Append("public static object ")
 			.Append(info.EffectiveDefaultValueCreatorMethodName)
 			.Append("(global::Microsoft.Maui.Controls.BindableObject bindable)\n")
 			.Append("{\n")
-			.Append("((")
-			.Append(classNameWithGenerics)
-			.Append(")bindable).")
 			.Append(info.InitializingPropertyName)
 			.Append(" = true;\n")
-			.Append("var defaultValue = ")
-			.Append("((")
-			.Append(classNameWithGenerics)
+			.Append("var defaultValue = ((")
+			.Append(fullDeclaringType)
 			.Append(")bindable).")
 			.Append(sanitizedPropertyName)
 			.Append(";\n")
-			.Append("((")
-			.Append(classNameWithGenerics)
-			.Append(")bindable).")
 			.Append(info.InitializingPropertyName)
 			.Append(" = false;\n")
 			.Append("return defaultValue;\n")
-			.Append("}\n");
+			.Append("}\n\n");
 	}
 }

src/CommunityToolkit.Maui.SourceGenerators.Internal/Models/Records.cs

@@ -9,8 +9,8 @@ public record BindablePropertyModel(string PropertyName, ITypeSymbol ReturnType,
 	public bool ShouldUsePropertyInitializer => HasInitializer && DefaultValueCreatorMethodName is "null";
 	public string BindablePropertyName => $"{PropertyName}Property";
 	public string BindablePropertyKeyName => $"{char.ToLower(PropertyName[0])}{PropertyName[1..]}PropertyKey";
-	public string EffectiveDefaultValueCreatorMethodName => ShouldUsePropertyInitializer ? $"__createDefault{PropertyName}" : DefaultValueCreatorMethodName;
-	public string InitializingPropertyName => $"__initializing{PropertyName}";
+	public string EffectiveDefaultValueCreatorMethodName => ShouldUsePropertyInitializer ? $"CreateDefault{PropertyName}" : DefaultValueCreatorMethodName;
+	public string InitializingPropertyName => $"IsInitializing{PropertyName}";
 
 }