Test for duplicate interface implementation instead of declaration

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

@@ -33,14 +33,12 @@ public INotifyPropertyChangedGenerator()
  {
  diagnostics = ImmutableArray<DiagnosticInfo>.Empty;
 
- INotifyPropertyChangedInfo? info = null;
-
  // Check if the type already implements INotifyPropertyChanged
- if (typeSymbol.AllInterfaces.Any(i => i.HasFullyQualifiedMetadataName("System.ComponentModel.INotifyPropertyChanged")))
+ if (typeSymbol.ImplementsInterfaceMember("System.ComponentModel.INotifyPropertyChanged"))
  {
  diagnostics = ImmutableArray.Create(DiagnosticInfo.Create(DuplicateINotifyPropertyChangedInterfaceForINotifyPropertyChangedAttributeError, typeSymbol, typeSymbol));
 
- goto End;
+ return null;
  }
 
  // Check if the type uses [INotifyPropertyChanged] or [ObservableObject] already (in the type hierarchy too)
@@ -49,15 +47,12 @@ public INotifyPropertyChangedGenerator()
  {
  diagnostics = ImmutableArray.Create(DiagnosticInfo.Create(InvalidAttributeCombinationForINotifyPropertyChangedAttributeError, typeSymbol, typeSymbol));
 
- goto End;
+ return null;
  }
 
  bool includeAdditionalHelperMethods = attributeData.GetNamedArgument("IncludeAdditionalHelperMethods", true);
 
- info = new INotifyPropertyChangedInfo(includeAdditionalHelperMethods);
-
- End:
- return info;
+ return new INotifyPropertyChangedInfo(includeAdditionalHelperMethods);
  }
 
  /// <inheritdoc/>

src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservableObjectGenerator.cs

@@ -2,12 +2,11 @@
 // 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.Extensions;
 using CommunityToolkit.Mvvm.SourceGenerators.Models;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using System.Collections.Immutable;
 using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators;
@@ -32,15 +31,15 @@ private protected override int ValidateTargetTypeAndGetInfo(INamedTypeSymbol typ
  diagnostics = ImmutableArray<DiagnosticInfo>.Empty;
 
  // Check if the type already implements INotifyPropertyChanged...
- if (typeSymbol.AllInterfaces.Any(i => i.HasFullyQualifiedMetadataName("System.ComponentModel.INotifyPropertyChanged")))
+ if (typeSymbol.ImplementsInterfaceMember("System.ComponentModel.INotifyPropertyChanged"))
  {
  diagnostics = ImmutableArray.Create(DiagnosticInfo.Create(DuplicateINotifyPropertyChangedInterfaceForObservableObjectAttributeError, typeSymbol, typeSymbol));
 
  goto End;
  }
 
  // ...or INotifyPropertyChanging
- if (typeSymbol.AllInterfaces.Any(i => i.HasFullyQualifiedMetadataName("System.ComponentModel.INotifyPropertyChanging")))
+ if (typeSymbol.ImplementsInterfaceMember("System.ComponentModel.INotifyPropertyChanging"))
  {
  diagnostics = ImmutableArray.Create(DiagnosticInfo.Create(DuplicateINotifyPropertyChangingInterfaceForObservableObjectAttributeError, typeSymbol, typeSymbol));
 

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/DiagnosticDescriptors.cs

@@ -35,51 +35,51 @@ internal static class DiagnosticDescriptors
  public const string AsyncVoidReturningRelayCommandMethodId = "MVVMTK0039";
 
  /// <summary>
- /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a duplicate declaration of <see cref="INotifyPropertyChanged"/> would happen.
+ /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a duplicate implementation of <see cref="INotifyPropertyChanged"/> would happen.
  /// <para>
- /// Format: <c>"Cannot apply [INotifyPropertyChangedAttribute] to type {0}, as it already declares the INotifyPropertyChanged interface"</c>.
+ /// Format: <c>"Cannot apply [INotifyPropertyChangedAttribute] to type {0}, as it already implements the INotifyPropertyChanged interface"</c>.
  /// </para>
  /// </summary>
  public static readonly DiagnosticDescriptor DuplicateINotifyPropertyChangedInterfaceForINotifyPropertyChangedAttributeError = new DiagnosticDescriptor(
  id: "MVVMTK0001",
  title: $"Duplicate {nameof(INotifyPropertyChanged)} definition",
- messageFormat: $"Cannot apply [INotifyPropertyChanged] to type {{0}}, as it already declares the {nameof(INotifyPropertyChanged)} interface",
+ messageFormat: $"Cannot apply [INotifyPropertyChanged] to type {{0}}, as it already implements the {nameof(INotifyPropertyChanged)} interface",
  category: typeof(INotifyPropertyChangedGenerator).FullName,
  defaultSeverity: DiagnosticSeverity.Error,
  isEnabledByDefault: true,
- description: $"Cannot apply [INotifyPropertyChanged] to a type that already declares the {nameof(INotifyPropertyChanged)} interface.",
+ description: $"Cannot apply [INotifyPropertyChanged] to a type that already implements the {nameof(INotifyPropertyChanged)} interface.",
  helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0001");
 
  /// <summary>
- /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a duplicate declaration of <see cref="INotifyPropertyChanged"/> would happen.
+ /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a duplicate implementation of <see cref="INotifyPropertyChanged"/> would happen.
  /// <para>
- /// Format: <c>"Cannot apply [ObservableObjectAttribute] to type {0}, as it already declares the INotifyPropertyChanged interface"</c>.
+ /// Format: <c>"Cannot apply [ObservableObjectAttribute] to type {0}, as it already implement the INotifyPropertyChanged interface"</c>.
  /// </para>
  /// </summary>
  public static readonly DiagnosticDescriptor DuplicateINotifyPropertyChangedInterfaceForObservableObjectAttributeError = new DiagnosticDescriptor(
  id: "MVVMTK0002",
  title: $"Duplicate {nameof(INotifyPropertyChanged)} definition",
- messageFormat: $"Cannot apply [ObservableObject] to type {{0}}, as it already declares the {nameof(INotifyPropertyChanged)} interface",
+ messageFormat: $"Cannot apply [ObservableObject] to type {{0}}, as it already implements the {nameof(INotifyPropertyChanged)} interface",
  category: typeof(ObservableObjectGenerator).FullName,
  defaultSeverity: DiagnosticSeverity.Error,
  isEnabledByDefault: true,
- description: $"Cannot apply [ObservableObject] to a type that already declares the {nameof(INotifyPropertyChanged)} interface.",
+ description: $"Cannot apply [ObservableObject] to a type that already implements the {nameof(INotifyPropertyChanged)} interface.",
  helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0002");
 
  /// <summary>
- /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a duplicate declaration of <see cref="INotifyPropertyChanging"/> would happen.
+ /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a duplicate implementation of <see cref="INotifyPropertyChanging"/> would happen.
  /// <para>
- /// Format: <c>"Cannot apply [ObservableObjectAttribute] to type {0}, as it already declares the INotifyPropertyChanging interface"</c>.
+ /// Format: <c>"Cannot apply [ObservableObjectAttribute] to type {0}, as it already implements the INotifyPropertyChanging interface"</c>.
  /// </para>
  /// </summary>
  public static readonly DiagnosticDescriptor DuplicateINotifyPropertyChangingInterfaceForObservableObjectAttributeError = new DiagnosticDescriptor(
  id: "MVVMTK0003",
  title: $"Duplicate {nameof(INotifyPropertyChanging)} definition",
- messageFormat: $"Cannot apply [ObservableObject] to type {{0}}, as it already declares the {nameof(INotifyPropertyChanging)} interface",
+ messageFormat: $"Cannot apply [ObservableObject] to type {{0}}, as it already implements the {nameof(INotifyPropertyChanging)} interface",
  category: typeof(ObservableObjectGenerator).FullName,
  defaultSeverity: DiagnosticSeverity.Error,
  isEnabledByDefault: true,
- description: $"Cannot apply [ObservableObject] to a type that already declares the {nameof(INotifyPropertyChanging)} interface.",
+ description: $"Cannot apply [ObservableObject] to a type that already implements the {nameof(INotifyPropertyChanging)} interface.",
  helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0003");
 
  /// <summary>

src/CommunityToolkit.Mvvm.SourceGenerators/Extensions/ITypeSymbolExtensions.cs

@@ -2,10 +2,11 @@
 // 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;
-using System.Linq;
 using CommunityToolkit.Mvvm.SourceGenerators.Helpers;
 using Microsoft.CodeAnalysis;
+using System;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 
@@ -249,4 +250,23 @@ static void BuildFrom(ISymbol? symbol, in ImmutableArrayBuilder<char> builder)
 
  BuildFrom(symbol, in builder);
  }
+
+ /// <summary>
+ /// Checks whether a given <see cref="ITypeSymbol"/> implements at least one members of the specified interface.
+ /// </summary>
+ /// <param name="symbol">The input <see cref="ITypeSymbol"/> instance.</param>
+ /// <param name="fullyQualifiedName">The fully qualified name of the interface.</param>
+ /// <returns>Whether at least a single interface member is implemented.</returns>
+ public static bool ImplementsInterfaceMember(this ITypeSymbol symbol, string fullyQualifiedName)
+ {
+ INamedTypeSymbol? interfaceSymbol = symbol.AllInterfaces.FirstOrDefault(x => x.HasFullyQualifiedMetadataName(fullyQualifiedName));
+ if (interfaceSymbol == null)
+ {
+ return false;
+ }
+
+ IEnumerable<ISymbol> interfaceMembers = interfaceSymbol.GetAllMembers();
+
+ return interfaceMembers.Any(x => symbol.FindImplementationForInterfaceMember(x) != null);
+ }
 }

tests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests/Test_SourceGeneratorsDiagnostics.cs

@@ -39,6 +39,22 @@ public partial class SampleViewModel : INotifyPropertyChanged
  """;
 
  VerifyGeneratedDiagnostics<INotifyPropertyChangedGenerator>(source, "MVVMTK0001");
+
+ string source_NoImplementation = """
+ using System.ComponentModel;
+ using CommunityToolkit.Mvvm.ComponentModel;
+
+ namespace MyApp
+ {
+ [INotifyPropertyChanged]
+ public partial class SampleViewModel : INotifyPropertyChanged
+ {
+
+ }
+ }
+ """;
+
+ VerifyGeneratedDiagnostics<INotifyPropertyChangedGenerator>(source_NoImplementation);
  }
 
  [TestMethod]
@@ -87,6 +103,22 @@ public partial class SampleViewModel : INotifyPropertyChanged
  """;
 
  VerifyGeneratedDiagnostics<ObservableObjectGenerator>(source, "MVVMTK0002");
+
+ string source_NoImplementation = """
+ using System.ComponentModel;
+ using CommunityToolkit.Mvvm.ComponentModel;
+
+ namespace MyApp
+ {
+ [ObservableObject]
+ public partial class SampleViewModel : INotifyPropertyChanged
+ {
+
+ }
+ }
+ """;
+
+ VerifyGeneratedDiagnostics<ObservableObjectGenerator>(source_NoImplementation);
  }
 
  [TestMethod]
@@ -134,6 +166,22 @@ public partial class SampleViewModel : INotifyPropertyChanging
  """;
 
  VerifyGeneratedDiagnostics<ObservableObjectGenerator>(source, "MVVMTK0003");
+
+ string source_NoImplementation = """
+ using System.ComponentModel;
+ using CommunityToolkit.Mvvm.ComponentModel;
+
+ namespace MyApp
+ {
+ [ObservableObject]
+ public partial class SampleViewModel : INotifyPropertyChanging
+ {
+
+ }
+ }
+ """;
+
+ VerifyGeneratedDiagnostics<ObservableObjectGenerator>(source_NoImplementation);
  }
 
  [TestMethod]