Don't propagate symbols in RelayCommandGenerator

CommunityToolkit.Mvvm.SourceGenerators/Extensions/ISymbolExtensions.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
@@ -64,6 +65,32 @@ internal static class ISymbolExtensions
         return false;
     }
 
+    /// <summary>
+    /// Tries to get an attribute with the specified full name.
+    /// </summary>
+    /// <param name="symbol">The input <see cref="ISymbol"/> instance to check.</param>
+    /// <param name="name">The attribute name to look for.</param>
+    /// <param name="attributeData">The resulting attribute, if it was found.</param>
+    /// <returns>Whether or not <paramref name="symbol"/> has an attribute with the specified name.</returns>
+    public static bool TryGetAttributeWithFullyQualifiedName(this ISymbol symbol, string name, [NotNullWhen(true)] out AttributeData? attributeData)
+    {
+        ImmutableArray<AttributeData> attributes = symbol.GetAttributes();
+
+        foreach (AttributeData attribute in attributes)
+        {
+            if (attribute.AttributeClass?.HasFullyQualifiedName(name) == true)
+            {
+                attributeData = attribute;
+
+                return true;
+            }
+        }
+
+        attributeData = null;
+
+        return false;
+    }
+
     /// <summary>
     /// Calculates the effective accessibility for a given symbol.
     /// </summary>

CommunityToolkit.Mvvm.SourceGenerators/Input/RelayCommandGenerator.cs

@@ -23,40 +23,33 @@ public sealed partial class RelayCommandGenerator : IIncrementalGenerator
     /// <inheritdoc/>
     public void Initialize(IncrementalGeneratorInitializationContext context)
     {
-        // Get all method declarations with at least one attribute
-        IncrementalValuesProvider<IMethodSymbol> methodSymbols =
+        // Gather info for all annotated command methods (starting from method declarations with at least one attribute)
+        IncrementalValuesProvider<(HierarchyInfo Hierarchy, Result<CommandInfo?> Info)> commandInfoWithErrors =
             context.SyntaxProvider
             .CreateSyntaxProvider(
                 static (node, _) => node is MethodDeclarationSyntax { Parent: ClassDeclarationSyntax, AttributeLists.Count: > 0 },
-                static (context, _) =>
+                static (context, token) =>
                 {
                     if (!context.SemanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
                     {
                         return default;
                     }
 
-                    return (IMethodSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!;
+                    IMethodSymbol methodSymbol = (IMethodSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node, token)!;
+
+                    // Filter the methods using [RelayCommand]
+                    if (!methodSymbol.TryGetAttributeWithFullyQualifiedName("global::CommunityToolkit.Mvvm.Input.RelayCommandAttribute", out AttributeData? attribute))
+                    {
+                        return default;
+                    }
+
+                    // Produce the incremental models
+                    HierarchyInfo hierarchy = HierarchyInfo.From(methodSymbol.ContainingType);
+                    CommandInfo? commandInfo = Execute.GetInfo(methodSymbol, attribute, out ImmutableArray<Diagnostic> diagnostics);
+
+                    return (Hierarchy: hierarchy, new Result<CommandInfo?>(commandInfo, diagnostics));
                 })
-            .Where(static item => item is not null)!;
-
-        // Filter the methods using [RelayCommand]
-        IncrementalValuesProvider<(IMethodSymbol Symbol, AttributeData Attribute)> methodSymbolsWithAttributeData =
-            methodSymbols
-            .Select(static (item, _) => (
-                item,
-                Attribute: item.GetAttributes().FirstOrDefault(a => a.AttributeClass?.HasFullyQualifiedName("global::CommunityToolkit.Mvvm.Input.RelayCommandAttribute") == true)))
-            .Where(static item => item.Attribute is not null)!;
-
-        // Gather info for all annotated command methods
-        IncrementalValuesProvider<(HierarchyInfo Hierarchy, Result<CommandInfo?> Info)> commandInfoWithErrors =
-            methodSymbolsWithAttributeData
-            .Select(static (item, _) =>
-            {
-                HierarchyInfo hierarchy = HierarchyInfo.From(item.Symbol.ContainingType);
-                CommandInfo? commandInfo = Execute.GetInfo(item.Symbol, item.Attribute, out ImmutableArray<Diagnostic> diagnostics);
-
-                return (hierarchy, new Result<CommandInfo?>(commandInfo, diagnostics));
-            });
+            .Where(static item => item.Hierarchy is not null);
 
         // Output the diagnostics
         context.ReportDiagnostics(commandInfoWithErrors.Select(static (item, _) => item.Info.Errors));
@@ -66,7 +59,7 @@ public sealed partial class RelayCommandGenerator : IIncrementalGenerator
             commandInfoWithErrors
             .Where(static item => item.Info.Value is not null)
             .Select(static (item, _) => (item.Hierarchy, item.Info.Value!))
-            .WithComparers(HierarchyInfo.Comparer.Default, CommandInfo.Comparer.Default);
+            .WithComparers(HierarchyInfo.Comparer.Default, CommandInfo.Comparer.Default);      
 
         // Generate the commands
         context.RegisterSourceOutput(commandInfo, static (context, item) =>