dotnet/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/INotifyPropertyChangedGenerator.cs

// 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.Collections.Immutable;
using System.Linq;
using CommunityToolkit.Mvvm.SourceGenerators.ComponentModel.Models;
using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
using CommunityToolkit.Mvvm.SourceGenerators.Helpers;
using CommunityToolkit.Mvvm.SourceGenerators.Models;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;

namespace CommunityToolkit.Mvvm.SourceGenerators;

/// <summary>
/// A source generator for the <c>INotifyPropertyChangedAttribute</c> type.
/// </summary>
[Generator(LanguageNames.CSharp)]
public sealed class INotifyPropertyChangedGenerator : TransitiveMembersGenerator<INotifyPropertyChangedInfo>
{
    /// <summary>
    /// Initializes a new instance of the <see cref="INotifyPropertyChangedGenerator"/> class.
    /// </summary>
    public INotifyPropertyChangedGenerator()
        : base("CommunityToolkit.Mvvm.ComponentModel.INotifyPropertyChangedAttribute")
    {
    }

    /// <inheritdoc/>
    private protected override INotifyPropertyChangedInfo? ValidateTargetTypeAndGetInfo(INamedTypeSymbol typeSymbol, AttributeData attributeData, Compilation compilation, out ImmutableArray<DiagnosticInfo> diagnostics)
    {
        diagnostics = ImmutableArray<DiagnosticInfo>.Empty;

        INotifyPropertyChangedInfo? info = null;

        // Check if the type already implements INotifyPropertyChanged
        if (typeSymbol.AllInterfaces.Any(i => i.HasFullyQualifiedMetadataName("System.ComponentModel.INotifyPropertyChanged")))
        {
            diagnostics = ImmutableArray.Create(DiagnosticInfo.Create(DuplicateINotifyPropertyChangedInterfaceForINotifyPropertyChangedAttributeError, typeSymbol, typeSymbol));

            goto End;
        }

        // Check if the type uses [INotifyPropertyChanged] or [ObservableObject] already (in the type hierarchy too)
        if (typeSymbol.HasOrInheritsAttributeWithFullyQualifiedMetadataName("CommunityToolkit.Mvvm.ComponentModel.ObservableObjectAttribute") ||
            typeSymbol.InheritsAttributeWithFullyQualifiedMetadataName("CommunityToolkit.Mvvm.ComponentModel.INotifyPropertyChangedAttribute"))
        {
            diagnostics = ImmutableArray.Create(DiagnosticInfo.Create(InvalidAttributeCombinationForINotifyPropertyChangedAttributeError, typeSymbol, typeSymbol));

            goto End;
        }

        bool includeAdditionalHelperMethods = attributeData.GetNamedArgument("IncludeAdditionalHelperMethods", true);

        info = new INotifyPropertyChangedInfo(includeAdditionalHelperMethods);

        End:
        return info;
    }

    /// <inheritdoc/>
    protected override ImmutableArray<MemberDeclarationSyntax> FilterDeclaredMembers(INotifyPropertyChangedInfo info, ImmutableArray<MemberDeclarationSyntax> memberDeclarations)
    {
        // If requested, only include the event and the basic methods to raise it, but not the additional helpers
        if (!info.IncludeAdditionalHelperMethods)
        {
            using ImmutableArrayBuilder<MemberDeclarationSyntax> selectedMembers = ImmutableArrayBuilder<MemberDeclarationSyntax>.Rent();

            foreach (MemberDeclarationSyntax memberDeclaration in memberDeclarations)
            {
                if (memberDeclaration is EventFieldDeclarationSyntax or MethodDeclarationSyntax { Identifier.ValueText: "OnPropertyChanged" })
                {
                    selectedMembers.Add(memberDeclaration);
                }
            }

            return selectedMembers.ToImmutable();
        }

        return memberDeclarations;
    }
}