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ObservableProperty: private setter #899

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ObservableProperty: private setter #899

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2 changes: 2 additions & 0 deletions src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/Models/PropertyInfo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.ComponentModel.Models;
/// <param name="IsOldPropertyValueDirectlyReferenced">Whether the old property value is being directly referenced.</param>
/// <param name="IsReferenceTypeOrUnconstraindTypeParameter">Indicates whether the property is of a reference type or an unconstrained type parameter.</param>
/// <param name="IncludeMemberNotNullOnSetAccessor">Indicates whether to include nullability annotations on the setter.</param>
/// <param name="UsePrivateKeywordOnSetAccessor">Indicates whether to use the private keyword for the generated setter.</param>
/// <param name="ForwardedAttributes">The sequence of forwarded attributes for the generated property.</param>
internal sealed record PropertyInfo(
string TypeNameWithNullabilityAnnotations,
Expand All @@ -32,5 +33,6 @@ internal sealed record PropertyInfo(
bool NotifyDataErrorInfo,
bool IsOldPropertyValueDirectlyReferenced,
bool IsReferenceTypeOrUnconstraindTypeParameter,
bool UsePrivateKeywordOnSetAccessor,
bool IncludeMemberNotNullOnSetAccessor,
EquatableArray<AttributeInfo> ForwardedAttributes);
28 changes: 28 additions & 0 deletions ...munityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.Execute.cs
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Expand Up @@ -117,6 +117,7 @@ public static bool TryGetInfo(
bool hasOrInheritsClassLevelNotifyPropertyChangedRecipients = false;
bool hasOrInheritsClassLevelNotifyDataErrorInfo = false;
bool hasAnyValidationAttributes = false;
bool usePrivateKeywordOnSetAccessor = false;
bool isOldPropertyValueDirectlyReferenced = IsOldPropertyValueDirectlyReferenced(fieldSymbol, propertyName);

token.ThrowIfCancellationRequested();
Expand Down Expand Up @@ -179,6 +180,14 @@ public static bool TryGetInfo(
continue;
}

// Check whether the generated setter should be private
if (SetterShouldBePrivate(attributeData))
{
usePrivateKeywordOnSetAccessor = true;

continue;
}

// Track the current attribute for forwarding if it is a validation attribute
if (attributeData.AttributeClass?.InheritsFromFullyQualifiedMetadataName("System.ComponentModel.DataAnnotations.ValidationAttribute") == true)
{
Expand Down Expand Up @@ -312,6 +321,7 @@ public static bool TryGetInfo(
notifyDataErrorInfo,
isOldPropertyValueDirectlyReferenced,
isReferenceTypeOrUnconstraindTypeParameter,
usePrivateKeywordOnSetAccessor,
includeMemberNotNullOnSetAccessor,
forwardedAttributes.ToImmutable());

Expand Down Expand Up @@ -687,6 +697,16 @@ private static bool TryGetNotifyDataErrorInfo(
return false;
}

/// <summary>
/// Checks whether the generated setter should be private.
/// </summary>
/// <param name="attributeData">The <see cref="AttributeData"/> instance for fieldSymbol.</param>
/// <returns>Whether or not the generated setter should be private.</returns>
private static bool SetterShouldBePrivate(AttributeData attributeData)
{
return attributeData.AttributeClass?.HasFullyQualifiedMetadataName("CommunityToolkit.Mvvm.ComponentModel.WithPrivateSetterAttribute") == true;
}

/// <summary>
/// Checks whether the generated code has to directly reference the old property value.
/// </summary>
Expand Down Expand Up @@ -1002,6 +1022,14 @@ public static MemberDeclarationSyntax GetPropertySyntax(PropertyInfo propertyInf
// }
AccessorDeclarationSyntax setAccessor = AccessorDeclaration(SyntaxKind.SetAccessorDeclaration).WithBody(Block(setterIfStatement));

// Add the private keyword if needed:
//
// private <SET_ACCESSOR>
if (propertyInfo.UsePrivateKeywordOnSetAccessor)
{
setAccessor = setAccessor.AddModifiers(Token(SyntaxKind.PrivateKeyword));
}

// Add the [MemberNotNull] attribute if needed:
//
// [MemberNotNull("<FIELD_NAME>")]
Expand Down
40 changes: 40 additions & 0 deletions src/CommunityToolkit.Mvvm/ComponentModel/Attributes/WithPrivateSetterAttribute.cs
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@@ -0,0 +1,40 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;

namespace CommunityToolkit.Mvvm.ComponentModel;

/// <summary>
/// An attribute that can be used to support <see cref="ObservablePropertyAttribute"/> in generated properties.
/// When this attribute is used, the generated property setter will be private.
/// This can be useful to prevent an unwanted property changes.
/// If this attribute is used in a field without <see cref="ObservablePropertyAttribute"/>, it is ignored.
/// <para>
/// This attribute can be used as follows:
/// <code>
/// partial class MyViewModel : ObservableObject
/// {
/// [ObservableProperty]
/// [WithPrivateSetter]
/// private string name;
/// }
/// </code>
/// </para>
/// And with this, code analogous to this will be generated:
/// <code>
/// partial class MyViewModel
/// {
/// public string Name
/// {
/// get => name;
/// private set => SetProperty(ref name, value);
/// }
/// }
/// </code>
/// </summary>
[AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = false)]
public sealed class WithPrivateSetterAttribute : Attribute
{
}
78 changes: 78 additions & 0 deletions tests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests/Test_SourceGeneratorsCodegen.cs
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Expand Up @@ -2733,6 +2733,84 @@ internal static class __KnownINotifyPropertyChangedArgs
VerifyGenerateSources(source, new[] { new ObservablePropertyGenerator() }, ("MyApp.MyViewModel.g.cs", result), ("__KnownINotifyPropertyChangingArgs.g.cs", null), ("__KnownINotifyPropertyChangedArgs.g.cs", changedArgs));
}

[TestMethod]
public void ObservableProperty_WithPrivateSetter()
{
string source = """
using System;
using CommunityToolkit.Mvvm.ComponentModel;

#nullable enable

namespace MyApp;

partial class MyViewModel : ObservableObject
{
[ObservableProperty]
[WithPrivateSetter]
private Guid id;
}
""";

string result = """
// <auto-generated/>
#pragma warning disable
#nullable enable
namespace MyApp
{
/// <inheritdoc/>
partial class MyViewModel
{
/// <inheritdoc cref="id"/>
[global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", <ASSEMBLY_VERSION>)]
[global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
public global::System.Guid Id
{
get => id;
private set
{
if (!global::System.Collections.Generic.EqualityComparer<global::System.Guid>.Default.Equals(id, value))
{
OnIdChanging(value);
OnIdChanging(default, value);
OnPropertyChanging(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangingArgs.Id);
id = value;
OnIdChanged(value);
OnIdChanged(default, value);
OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.Id);
}
}
}

/// <summary>Executes the logic for when <see cref="Id"/> is changing.</summary>
/// <param name="value">The new property value being set.</param>
/// <remarks>This method is invoked right before the value of <see cref="Id"/> is changed.</remarks>
[global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", <ASSEMBLY_VERSION>)]
partial void OnIdChanging(global::System.Guid value);
/// <summary>Executes the logic for when <see cref="Id"/> is changing.</summary>
/// <param name="oldValue">The previous property value that is being replaced.</param>
/// <param name="newValue">The new property value being set.</param>
/// <remarks>This method is invoked right before the value of <see cref="Id"/> is changed.</remarks>
[global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", <ASSEMBLY_VERSION>)]
partial void OnIdChanging(global::System.Guid oldValue, global::System.Guid newValue);
/// <summary>Executes the logic for when <see cref="Id"/> just changed.</summary>
/// <param name="value">The new property value that was set.</param>
/// <remarks>This method is invoked right after the value of <see cref="Id"/> is changed.</remarks>
[global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", <ASSEMBLY_VERSION>)]
partial void OnIdChanged(global::System.Guid value);
/// <summary>Executes the logic for when <see cref="Id"/> just changed.</summary>
/// <param name="oldValue">The previous property value that was replaced.</param>
/// <param name="newValue">The new property value that was set.</param>
/// <remarks>This method is invoked right after the value of <see cref="Id"/> is changed.</remarks>
[global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator", <ASSEMBLY_VERSION>)]
partial void OnIdChanged(global::System.Guid oldValue, global::System.Guid newValue);
}
}
""";

VerifyGenerateSources(source, new[] { new ObservablePropertyGenerator() }, ("MyApp.MyViewModel.g.cs", result));
}

/// <summary>
/// Generates the requested sources
/// </summary>
Expand Down