Add [field:] and [property:] support for [RelayCommand] methods

src/CommunityToolkit.Mvvm.SourceGenerators/AnalyzerReleases.Shipped.md

@@ -49,3 +49,11 @@ MVVMTK0032 | CommunityToolkit.Mvvm.SourceGenerators.INotifyPropertyChangedGenera
 MVVMTK0033 | CommunityToolkit.Mvvm.SourceGenerators.ObservableObjectGenerator | Warning | See https://aka.ms/mvvmtoolkit/errors/mvvmtk0033
 MVVMTK0034 | CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Warning | See https://aka.ms/mvvmtoolkit/errors/mvvmtk0034
 MVVMTK0035 | CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | See https://aka.ms/mvvmtoolkit/errors/mvvmtk0035
+
+## Release 8.2
+
+### New Rules
+
+Rule ID | Category | Severity | Notes
+--------|----------|----------|-------
+MVVMTK0036 | CommunityToolkit.Mvvm.SourceGenerators.RelayCommandGenerator | Error | See https://aka.ms/mvvmtoolkit/errors/mvvmtk0036

src/CommunityToolkit.Mvvm.SourceGenerators/CommunityToolkit.Mvvm.SourceGenerators.projitems

@@ -45,6 +45,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\FieldWithOrphanedDependentObservablePropertyAttributesAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\FieldReferenceForObservablePropertyFieldAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\UnsupportedCSharpLanguageVersionAnalyzer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Suppressors\RelayCommandAttributeWithFieldOrPropertyTargetDiagnosticSuppressor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Suppressors\ObservablePropertyAttributeWithPropertyTargetDiagnosticSuppressor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\DiagnosticDescriptors.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\SuppressionDescriptors.cs" />
@@ -54,10 +55,12 @@
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\INamedTypeSymbolExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\IncrementalGeneratorInitializationContextExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\IncrementalValuesProviderExtensions.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Extensions\SymbolInfoExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\ISymbolExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\SourceProductionContextExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\ITypeSymbolExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\MemberDeclarationSyntaxExtensions.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Extensions\SyntaxTokenExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\SyntaxNodeExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\TypeDeclarationSyntaxExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Helpers\EquatableArray{T}.cs" />

src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.Execute.cs

@@ -193,7 +193,7 @@ public static bool TryGetInfo(
                 // Only look for attribute lists explicitly targeting the (generated) property. Roslyn will normally emit a
                 // CS0657 warning (invalid target), but that is automatically suppressed by a dedicated diagnostic suppressor
                 // that recognizes uses of this target specifically to support [ObservableProperty].
-                if (attributeList.Target?.Identifier.Kind() is not SyntaxKind.PropertyKeyword)
+                if (attributeList.Target?.Identifier is not SyntaxToken(SyntaxKind.PropertyKeyword))
                 {
                     continue;
                 }
@@ -214,12 +214,7 @@ public static bool TryGetInfo(
                     // There is no need to validate anything here: the attribute will be forwarded as is, and then Roslyn will validate on the
                     // generated property. Users will get the same validation they'd have had directly over the field. The only drawback is the
                     // lack of IntelliSense when constructing attributes over the field, but this is the best we can do from this end anyway.
-                    SymbolInfo attributeSymbolInfo = semanticModel.GetSymbolInfo(attribute, token);
-
-                    // Check if the attribute type can be resolved, and emit a diagnostic if that is not the case. This happens if eg. the
-                    // attribute type is spelled incorrectly, or if a user is missing the using directive for the attribute type being used.
-                    if ((attributeSymbolInfo.Symbol ?? attributeSymbolInfo.CandidateSymbols.SingleOrDefault()) is not ISymbol attributeSymbol ||
-                        (attributeSymbol as INamedTypeSymbol ?? attributeSymbol.ContainingType) is not INamedTypeSymbol attributeTypeSymbol)
+                    if (!semanticModel.GetSymbolInfo(attribute, token).TryGetAttributeTypeSymbol(out INamedTypeSymbol? attributeTypeSymbol))
                     {
                         builder.Add(
                             InvalidPropertyTargetedAttributeOnObservablePropertyField,

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

@@ -589,4 +589,20 @@ internal static class DiagnosticDescriptors
         isEnabledByDefault: true,
         description: "All attributes targeting the generated property for a field annotated with [ObservableProperty] must correctly be resolved to valid types.",
         helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0035");
+
+    /// <summary>
+    /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a method with <c>[RelayCommand]</c> is using an invalid attribute targeting the field or property.
+    /// <para>
+    /// Format: <c>"The method {0} annotated with [RelayCommand] is using attribute "{1}" which was not recognized as a valid type (are you missing a using directive?)"</c>.
+    /// </para>
+    /// </summary>
+    public static readonly DiagnosticDescriptor InvalidFieldOrPropertyTargetedAttributeOnRelayCommandMethod = new DiagnosticDescriptor(
+        id: "MVVMTK0036",
+        title: "Invalid field targeted attribute type",
+        messageFormat: "The method {0} annotated with [RelayCommand] is using attribute \"{1}\" which was not recognized as a valid type (are you missing a using directive?)",
+        category: typeof(RelayCommandGenerator).FullName,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "All attributes targeting the generated field or property for a method annotated with [RelayCommand] must correctly be resolved to valid types.",
+        helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0036");
 }

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

@@ -12,10 +12,18 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.Diagnostics;
 internal static class SuppressionDescriptors
 {
     /// <summary>
-    /// Gets a <see cref="SuppressionDescriptor"/> for a field using [ObservableProperty] with on attribute list targeting a property.
+    /// Gets a <see cref="SuppressionDescriptor"/> for a field using [ObservableProperty] with an attribute list targeting a property.
     /// </summary>
     public static readonly SuppressionDescriptor PropertyAttributeListForObservablePropertyField = new(
         id: "MVVMTKSPR0001",
         suppressedDiagnosticId: "CS0657",
         justification: "Fields using [ObservableProperty] can use [property:] attribute lists to forward attributes to the generated properties");
+
+    /// <summary>
+    /// Gets a <see cref="SuppressionDescriptor"/> for a method using [RelayCommand] with an attribute list targeting a field or property.
+    /// </summary>
+    public static readonly SuppressionDescriptor FieldOrPropertyAttributeListForRelayCommandMethod = new(
+        id: "MVVMTKSPR0002",
+        suppressedDiagnosticId: "CS0657",
+        justification: "Methods using [RelayCommand] can use [field:] and [property:] attribute lists to forward attributes to the generated fields and properties");
 }

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Suppressors/ObservablePropertyAttributeWithPropertyTargetDiagnosticSuppressor.cs

@@ -3,7 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
-using System.Linq;
+using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
@@ -19,7 +19,7 @@ namespace CommunityToolkit.Mvvm.SourceGenerators;
 /// <para>
 /// That is, this diagnostic suppressor will suppress the following diagnostic:
 /// <code>
-/// public class MyViewModel : ObservableObject
+/// public partial class MyViewModel : ObservableObject
 /// {
 ///     [ObservableProperty]
 ///     [property: JsonPropertyName("Name")]
@@ -53,7 +53,7 @@ public override void ReportSuppressions(SuppressionAnalysisContext context)
                 // Check if the field is using [ObservableProperty], in which case we should suppress the warning
                 if (declaredSymbol is IFieldSymbol fieldSymbol &&
                     semanticModel.Compilation.GetTypeByMetadataName("CommunityToolkit.Mvvm.ComponentModel.ObservablePropertyAttribute") is INamedTypeSymbol observablePropertySymbol &&
-                    fieldSymbol.GetAttributes().Select(attribute => attribute.AttributeClass).Contains(observablePropertySymbol, SymbolEqualityComparer.Default))
+                    fieldSymbol.HasAttributeWithType(observablePropertySymbol))
                 {
                     context.ReportSuppression(Suppression.Create(PropertyAttributeListForObservablePropertyField, diagnostic));
                 }

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Suppressors/RelayCommandAttributeWithFieldOrPropertyTargetDiagnosticSuppressor.cs

@@ -0,0 +1,65 @@
+// 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 CommunityToolkit.Mvvm.SourceGenerators.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.SuppressionDescriptors;
+
+namespace CommunityToolkit.Mvvm.SourceGenerators;
+
+/// <summary>
+/// <para>
+/// A diagnostic suppressor to suppress CS0657 warnings for methods with [RelayCommand] using a [field:] or [property:] attribute list.
+/// </para>
+/// <para>
+/// That is, this diagnostic suppressor will suppress the following diagnostic:
+/// <code>
+/// public partial class MyViewModel : ObservableObject
+/// {
+///     [RelayCommand]
+///     [field: JsonIgnore]
+///     [property: SomeOtherAttribute]
+///     private void DoSomething()
+///     {
+///     }
+/// }
+/// </code>
+/// </para>
+/// </summary>
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class RelayCommandAttributeWithFieldOrPropertyTargetDiagnosticSuppressor : DiagnosticSuppressor
+{
+    /// <inheritdoc/>
+    public override ImmutableArray<SuppressionDescriptor> SupportedSuppressions => ImmutableArray.Create(FieldOrPropertyAttributeListForRelayCommandMethod);
+
+    /// <inheritdoc/>
+    public override void ReportSuppressions(SuppressionAnalysisContext context)
+    {
+        foreach (Diagnostic diagnostic in context.ReportedDiagnostics)
+        {
+            SyntaxNode? syntaxNode = diagnostic.Location.SourceTree?.GetRoot(context.CancellationToken).FindNode(diagnostic.Location.SourceSpan);
+
+            // Check that the target is effectively [field:] or [property:] over a method declaration, which is the case we're looking for
+            if (syntaxNode is AttributeTargetSpecifierSyntax { Parent.Parent: MethodDeclarationSyntax methodDeclaration, Identifier: SyntaxToken(SyntaxKind.FieldKeyword or SyntaxKind.PropertyKeyword) })
+            {
+                SemanticModel semanticModel = context.GetSemanticModel(syntaxNode.SyntaxTree);
+
+                // Get the method symbol from the first variable declaration
+                ISymbol? declaredSymbol = semanticModel.GetDeclaredSymbol(methodDeclaration, context.CancellationToken);
+
+                // Check if the method is using [RelayCommand], in which case we should suppress the warning
+                if (declaredSymbol is IMethodSymbol methodSymbol &&
+                    semanticModel.Compilation.GetTypeByMetadataName("CommunityToolkit.Mvvm.Input.RelayCommandAttribute") is INamedTypeSymbol relayCommandSymbol &&
+                    methodSymbol.HasAttributeWithType(relayCommandSymbol))
+                {
+                    context.ReportSuppression(Suppression.Create(FieldOrPropertyAttributeListForRelayCommandMethod, diagnostic));
+                }
+            }
+        }
+    }
+}

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

@@ -0,0 +1,48 @@
+// 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.Diagnostics.CodeAnalysis;
+using Microsoft.CodeAnalysis;
+
+namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
+
+/// <summary>
+/// Extension methods for the <see cref="SymbolInfo"/> type.
+/// </summary>
+internal static class SymbolInfoExtensions
+{
+    /// <summary>
+    /// Tries to get the resolved attribute type symbol from a given <see cref="SymbolInfo"/> value.
+    /// </summary>
+    /// <param name="symbolInfo">The <see cref="SymbolInfo"/> value to check.</param>
+    /// <param name="typeSymbol">The resulting attribute type symbol, if correctly resolved.</param>
+    /// <returns>Whether <paramref name="symbolInfo"/> is resolved to a symbol.</returns>
+    /// <remarks>
+    /// This can be used to ensure users haven't eg. spelled names incorrecty or missed a using directive. Normally, code would just
+    /// not compile if that was the case, but that doesn't apply for attributes using invalid targets. In that case, Roslyn will ignore
+    /// any errors, meaning the generator has to validate the type symbols are correctly resolved on its own.
+    /// </remarks>
+    public static bool TryGetAttributeTypeSymbol(this SymbolInfo symbolInfo, [NotNullWhen(true)] out INamedTypeSymbol? typeSymbol)
+    {
+        ISymbol? attributeSymbol = symbolInfo.Symbol;
+
+        // If no symbol is selected and there is a single candidate symbol, use that
+        if (attributeSymbol is null && symbolInfo.CandidateSymbols is [ISymbol candidateSymbol])
+        {
+            attributeSymbol = candidateSymbol;
+        }
+
+        // Extract the symbol from either the current one or the containing type
+        if ((attributeSymbol as INamedTypeSymbol ?? attributeSymbol?.ContainingType) is not INamedTypeSymbol resultingSymbol)
+        {
+            typeSymbol = null;
+
+            return false;
+        }
+
+        typeSymbol = resultingSymbol;
+
+        return true;
+    }
+}

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

@@ -0,0 +1,24 @@
+// 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 Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+
+namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
+
+/// <summary>
+/// Extension methods for the <see cref="SyntaxToken"/> type.
+/// </summary>
+internal static class SyntaxTokenExtensions
+{
+    /// <summary>
+    /// Deconstructs a <see cref="SyntaxToken"/> into its <see cref="SyntaxKind"/> value.
+    /// </summary>
+    /// <param name="syntaxToken">The input <see cref="SyntaxToken"/> value.</param>
+    /// <param name="syntaxKind">The resulting <see cref="SyntaxKind"/> value for <paramref name="syntaxToken"/>.</param>
+    public static void Deconstruct(this SyntaxToken syntaxToken, out SyntaxKind syntaxKind)
+    {
+        syntaxKind = syntaxToken.Kind();
+    }
+}

src/CommunityToolkit.Mvvm.SourceGenerators/Input/Models/CommandInfo.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using CommunityToolkit.Mvvm.SourceGenerators.ComponentModel.Models;
 using CommunityToolkit.Mvvm.SourceGenerators.Helpers;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.Input.Models;
@@ -22,6 +23,8 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.Input.Models;
 /// <param name="AllowConcurrentExecutions">Whether or not concurrent executions have been enabled.</param>
 /// <param name="FlowExceptionsToTaskScheduler">Whether or not exceptions should flow to the task scheduler.</param>
 /// <param name="IncludeCancelCommand">Whether or not to also generate a cancel command.</param>
+/// <param name="ForwardedFieldAttributes">The sequence of forwarded attributes for the generated field.</param>
+/// <param name="ForwardedPropertyAttributes">The sequence of forwarded attributes for the generated property.</param>
 internal sealed record CommandInfo(
     string MethodName,
     string FieldName,
@@ -35,4 +38,6 @@ internal sealed record CommandInfo(
     CanExecuteExpressionType? CanExecuteExpressionType,
     bool AllowConcurrentExecutions,
     bool FlowExceptionsToTaskScheduler,
-    bool IncludeCancelCommand);
+    bool IncludeCancelCommand,
+    EquatableArray<AttributeInfo> ForwardedFieldAttributes,
+    EquatableArray<AttributeInfo> ForwardedPropertyAttributes);