Added ICommandGenerator diagnostics

Author: Sergio0694

Microsoft.Toolkit.Mvvm.SourceGenerators/AnalyzerReleases.Unshipped.md

@@ -14,4 +14,6 @@ MVVMTK0006 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservableObjectGenerator |
 MVVMTK0007 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservableRecipientGenerator | Error | See https://aka.ms/mvvmtoolkit
 MVVMTK0008 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservableRecipientGenerator | Error | See https://aka.ms/mvvmtoolkit
 MVVMTK0009 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | See https://aka.ms/mvvmtoolkit
-MVVMTK0010 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | See https://aka.ms/mvvmtoolkit
+MVVMTK0010 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | See https://aka.ms/mvvmtoolkit
+MVVMTK0011 | Microsoft.Toolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | See https://aka.ms/mvvmtoolkit
+MVVMTK0012 | Microsoft.Toolkit.Mvvm.SourceGenerators.ICommandGenerator | Error | See https://aka.ms/mvvmtoolkit

Microsoft.Toolkit.Mvvm.SourceGenerators/Diagnostics/DiagnosticDescriptors.cs

@@ -5,6 +5,7 @@
 using System.ComponentModel;
 using Microsoft.CodeAnalysis;
 using Microsoft.Toolkit.Mvvm.ComponentModel;
+using Microsoft.Toolkit.Mvvm.Input;
 
 namespace Microsoft.Toolkit.Mvvm.SourceGenerators.Diagnostics
 {
@@ -150,7 +151,7 @@ internal static class DiagnosticDescriptors
         public static readonly DiagnosticDescriptor MissingObservableValidatorInheritanceError = new(
             id: "MVVMTK0009",
             title: "Missing ObservableValidator inheritance",
-            messageFormat: $"The field {{0}}.{{1}} cannot be used to generate an observable property, as it has {{2}} validation attribute(s) but is declared in a type that doesn't inherit from ObservableValidator",
+            messageFormat: "The field {0}.{1} cannot be used to generate an observable property, as it has {2} validation attribute(s) but is declared in a type that doesn't inherit from ObservableValidator",
             category: typeof(ObservablePropertyGenerator).FullName,
             defaultSeverity: DiagnosticSeverity.Error,
             isEnabledByDefault: true,
@@ -172,5 +173,37 @@ internal static class DiagnosticDescriptors
             isEnabledByDefault: true,
             description: $"The {nameof(ObservablePropertyGenerator)} generator encountered an error while processing a type. Please report this issue at https://aka.ms/mvvmtoolkit.",
             helpLinkUri: "https://aka.ms/mvvmtoolkit");
+
+        /// <summary>
+        /// Gets a <see cref="DiagnosticDescriptor"/> indicating when <see cref="ICommandGenerator"/> failed to run on a given type.
+        /// <para>
+        /// Format: <c>"The generator ICommandGenerator failed to execute on type {0}"</c>.
+        /// </para>
+        /// </summary>
+        public static readonly DiagnosticDescriptor ICommandGeneratorError = new(
+            id: "MVVMTK0011",
+            title: $"Internal error for {nameof(ICommandGenerator)}",
+            messageFormat: $"The generator {nameof(ICommandGenerator)} failed to execute on type {{0}}",
+            category: typeof(ICommandGenerator).FullName,
+            defaultSeverity: DiagnosticSeverity.Error,
+            isEnabledByDefault: true,
+            description: $"The {nameof(ICommandGenerator)} generator encountered an error while processing a type. Please report this issue at https://aka.ms/mvvmtoolkit.",
+            helpLinkUri: "https://aka.ms/mvvmtoolkit");
+
+        /// <summary>
+        /// Gets a <see cref="DiagnosticDescriptor"/> indicating when an annotated method to generate a command for has an invalid signature.
+        /// <para>
+        /// Format: <c>"The method {0}.{1} cannot be used to generate a command property, as its signature isn't compatible with any of the existing relay command types"</c>.
+        /// </para>
+        /// </summary>
+        public static readonly DiagnosticDescriptor InvalidICommandMethodSignatureError = new(
+            id: "MVVMTK0012",
+            title: "Invalid ICommand method signature",
+            messageFormat: "The method {0}.{1} cannot be used to generate a command property, as its signature isn't compatible with any of the existing relay command types",
+            category: typeof(ICommandGenerator).FullName,
+            defaultSeverity: DiagnosticSeverity.Error,
+            isEnabledByDefault: true,
+            description: $"Cannot apply [{nameof(ICommandAttribute)}] to methods with a signature that doesn't match any of the existing relay command types.",
+            helpLinkUri: "https://aka.ms/mvvmtoolkit");
     }
 }

Microsoft.Toolkit.Mvvm.SourceGenerators/Input/ICommandGenerator.cs

@@ -13,9 +13,11 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.Toolkit.Mvvm.Input;
+using Microsoft.Toolkit.Mvvm.SourceGenerators.Diagnostics;
 using Microsoft.Toolkit.Mvvm.SourceGenerators.Extensions;
 using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 using static Microsoft.CodeAnalysis.SymbolDisplayTypeQualificationStyle;
+using static Microsoft.Toolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
 
 namespace Microsoft.Toolkit.Mvvm.SourceGenerators
 {
@@ -52,7 +54,7 @@ public void Execute(GeneratorExecutionContext context)
                     }
                     catch
                     {
-                        // TODO
+                        context.ReportDiagnostic(ICommandGeneratorError, classDeclaration, items.Key);
                     }
                 }
             }
@@ -136,6 +138,8 @@ private static IEnumerable<MemberDeclarationSyntax> CreateCommandMembers(Generat
                 out ITypeSymbol? commandClassTypeSymbol,
                 out ITypeSymbol? delegateTypeSymbol))
             {
+                context.ReportDiagnostic(InvalidICommandMethodSignatureError, methodSymbol, methodSymbol.ContainingType, methodSymbol);
+
                 return Array.Empty<MemberDeclarationSyntax>();
             }
 

UnitTests/UnitTests.SourceGenerators/Test_SourceGeneratorsDiagnostics.cs

@@ -221,6 +221,25 @@ public partial class SampleViewModel
             VerifyGeneratedDiagnostics<ObservablePropertyGenerator>(source, "MVVMTK0009");
         }
 
+        [TestCategory("Mvvm")]
+        [TestMethod]
+        public void InvalidICommandMethodSignatureError()
+        {
+            string source = @"
+            using Microsoft.Toolkit.Mvvm.Input;
+
+            namespace MyApp
+            {
+                public partial class SampleViewModel
+                {
+                    [ICommand]
+                    private string GreetUser() => ""Hello world!"";
+                }
+            }";
+
+            VerifyGeneratedDiagnostics<ICommandGenerator>(source, "MVVMTK0012");
+        }
+
         /// <summary>
         /// Verifies the output of a source generator.
         /// </summary>