.NET: Fix source generator bug that silently drops base class handler registrations for protocol-only partial executors (#4751)

* Fix source generator bug that silently drops base class handler registrations for protocol-only partial executors

* Fixed xml comments and variable naming.

dotnet/samples/03-workflows/Agents/CustomAgentExecutors/Program.cs

@@ -61,6 +61,12 @@ public static class Program
             {
                 Console.WriteLine($"{outputEvent}");
             }
+
+            if (evt is WorkflowErrorEvent errorEvent)
+            {
+                Console.WriteLine($"Workflow error: {errorEvent.Exception?.Message}");
+                Console.WriteLine($"Details: {errorEvent.Exception}");
+            }
         }
     }
 }
@@ -175,7 +181,9 @@ internal sealed class FeedbackEvent(FeedbackResult feedbackResult) : WorkflowEve
 /// <summary>
 /// A custom executor that uses an AI agent to provide feedback on a slogan.
 /// </summary>
-internal sealed class FeedbackExecutor : Executor<SloganResult>
+[SendsMessage(typeof(FeedbackResult))]
+[YieldsOutput(typeof(string))]
+internal sealed partial class FeedbackExecutor : Executor<SloganResult>
 {
     private readonly AIAgent _agent;
     private AgentSession? _session;

dotnet/src/Microsoft.Agents.AI.Workflows.Generators/Analysis/SemanticAnalyzer.cs

@@ -68,7 +68,7 @@ internal static class SemanticAnalyzer
         string classKey = GetClassKey(classSymbol);
         bool isPartialClass = IsPartialClass(classSymbol, cancellationToken);
         bool derivesFromExecutor = DerivesFromExecutor(classSymbol);
-        bool configureProtocol = HasConfigureProtocolDefined(classSymbol);
+        bool hasManualConfigureProtocol = HasConfigureProtocolDefined(classSymbol);
 
         // Extract class metadata
         string? @namespace = classSymbol.ContainingNamespace?.IsGlobalNamespace == true
@@ -97,7 +97,7 @@ internal static class SemanticAnalyzer
         return new MethodAnalysisResult(
             classKey, @namespace, className, genericParameters, isNested, containingTypeChain,
             baseHasConfigureProtocol, classSendTypes, classYieldTypes,
-            isPartialClass, derivesFromExecutor, configureProtocol,
+            isPartialClass, derivesFromExecutor, hasManualConfigureProtocol,
             classLocation,
             handler,
             Diagnostics: new ImmutableEquatableArray<DiagnosticInfo>(methodDiagnostics.ToImmutable()));
@@ -149,7 +149,7 @@ internal static class SemanticAnalyzer
             return AnalysisResult.WithDiagnostics(allDiagnostics.ToImmutable());
         }
 
-        if (first.HasManualConfigureRoutes)
+        if (first.HasManualConfigureProtocol)
         {
             allDiagnostics.Add(Diagnostic.Create(
                 DiagnosticDescriptors.ConfigureProtocolAlreadyDefined,
@@ -212,6 +212,7 @@ internal static class SemanticAnalyzer
         bool isPartialClass = IsPartialClass(classSymbol, cancellationToken);
         bool derivesFromExecutor = DerivesFromExecutor(classSymbol);
         bool hasManualConfigureProtocol = HasConfigureProtocolDefined(classSymbol);
+        bool baseHasConfigureProtocol = BaseHasConfigureProtocol(classSymbol);
 
         string? @namespace = classSymbol.ContainingNamespace?.IsGlobalNamespace == true
             ? null
@@ -241,6 +242,7 @@ internal static class SemanticAnalyzer
                     isPartialClass,
                     derivesFromExecutor,
                     hasManualConfigureProtocol,
+                    baseHasConfigureProtocol,
                     classLocation,
                     typeName,
                     attributeKind));
@@ -321,7 +323,7 @@ internal static class SemanticAnalyzer
             first.GenericParameters,
             first.IsNested,
             first.ContainingTypeChain,
-            BaseHasConfigureProtocol: false, // Not relevant for protocol-only
+            first.BaseHasConfigureProtocol,
             Handlers: ImmutableEquatableArray<HandlerInfo>.Empty,
             ClassSendTypes: new ImmutableEquatableArray<string>(sendTypes.ToImmutable()),
             ClassYieldTypes: new ImmutableEquatableArray<string>(yieldTypes.ToImmutable()));

dotnet/src/Microsoft.Agents.AI.Workflows.Generators/Models/ClassProtocolInfo.cs

@@ -5,7 +5,7 @@ namespace Microsoft.Agents.AI.Workflows.Generators.Models;
 /// <summary>
 /// Represents protocol type information extracted from class-level [SendsMessage] or [YieldsOutput] attributes.
 /// Used by the incremental generator pipeline to capture classes that declare protocol types
-/// but may not have [MessageHandler] methods (e.g., when ConfigureRoutes is manually implemented).
+/// but may not have [MessageHandler] methods (e.g., when ConfigureProtocol is manually implemented).
 /// </summary>
 /// <param name="ClassKey">Unique identifier for the class (fully qualified name).</param>
 /// <param name="Namespace">The namespace of the class.</param>
@@ -15,7 +15,8 @@ namespace Microsoft.Agents.AI.Workflows.Generators.Models;
 /// <param name="ContainingTypeChain">The chain of containing types for nested classes. Empty if not nested.</param>
 /// <param name="IsPartialClass">Whether the class is declared as partial.</param>
 /// <param name="DerivesFromExecutor">Whether the class derives from Executor.</param>
-/// <param name="HasManualConfigureRoutes">Whether the class has a manually defined ConfigureRoutes method.</param>
+/// <param name="HasManualConfigureProtocol">Whether the class has a manually defined ConfigureProtocol method.</param>
+/// <param name="BaseHasConfigureProtocol">Whether a base class already overrides ConfigureProtocol.</param>
 /// <param name="ClassLocation">Location info for diagnostics.</param>
 /// <param name="TypeName">The fully qualified type name from the attribute.</param>
 /// <param name="AttributeKind">Whether this is from a SendsMessage or YieldsOutput attribute.</param>
@@ -28,7 +29,8 @@ internal sealed record ClassProtocolInfo(
     string ContainingTypeChain,
     bool IsPartialClass,
     bool DerivesFromExecutor,
-    bool HasManualConfigureRoutes,
+    bool HasManualConfigureProtocol,
+    bool BaseHasConfigureProtocol,
     DiagnosticLocationInfo? ClassLocation,
     string TypeName,
     ProtocolAttributeKind AttributeKind)
@@ -38,5 +40,5 @@ internal sealed record ClassProtocolInfo(
     /// </summary>
     public static ClassProtocolInfo Empty { get; } = new(
         string.Empty, null, string.Empty, null, false, string.Empty,
-        false, false, false, null, string.Empty, ProtocolAttributeKind.Send);
+        false, false, false, false, null, string.Empty, ProtocolAttributeKind.Send);
 }

dotnet/src/Microsoft.Agents.AI.Workflows.Generators/Models/MethodAnalysisResult.cs

@@ -8,7 +8,7 @@ namespace Microsoft.Agents.AI.Workflows.Generators.Models;
 /// Uses value-equatable types to support incremental generator caching.
 /// </summary>
 /// <remarks>
-/// Class-level validation (IsPartialClass, DerivesFromExecutor, HasManualConfigureRoutes)
+/// Class-level validation (IsPartialClass, DerivesFromExecutor, HasManualConfigureProtocol)
 /// is extracted here but validated once per class in CombineMethodResults to avoid
 /// redundant validation work when a class has multiple handlers.
 /// </remarks>
@@ -29,7 +29,7 @@ internal sealed record MethodAnalysisResult(
     // Class-level facts (used for validation in CombineMethodResults)
     bool IsPartialClass,
     bool DerivesFromExecutor,
-    bool HasManualConfigureRoutes,
+    bool HasManualConfigureProtocol,
 
     // Class location for diagnostics (value-equatable)
     DiagnosticLocationInfo? ClassLocation,

dotnet/tests/Microsoft.Agents.AI.Workflows.Generators.UnitTests/ExecutorRouteGeneratorTests.cs

@@ -651,7 +651,7 @@ public class ExecutorRouteGeneratorTests
     }
 
     [Fact]
-    public void PartialClass_SendsYieldsInBothFiles_GeneratesAlOverrides()
+    public void PartialClass_SendsYieldsInBothFiles_GeneratesAllOverrides()
     {
         // File 1: Partial with one handler
         var file1 = """
@@ -700,7 +700,7 @@ public class ExecutorRouteGeneratorTests
         generated.Should().RegisterSentMessageType("string")
                       .And.RegisterSentMessageType("int")
                       .And.RegisterYieldedOutputType("string")
-                      .And.RegisterYieldedOutputType("string");
+                      .And.RegisterYieldedOutputType("int");
     }
 
     #endregion
@@ -1046,6 +1046,85 @@ public class ExecutorRouteGeneratorTests
                       .And.RegisterSentMessageType("global::TestNamespace.BroadcastMessage");
     }
 
+    [Fact]
+    public void ProtocolOnly_DerivesFromExecutorOfT_GeneratesBaseCall()
+    {
+        // A protocol-only partial executor deriving from Executor<T>
+        // has a base class that already overrides ConfigureProtocol. The generator must emit
+        // "return base.ConfigureProtocol(protocolBuilder)" so inherited handler registrations
+        // are preserved — not "return protocolBuilder" which silently drops them.
+        var source = """
+            using System;
+            using System.Threading;
+            using System.Threading.Tasks;
+            using Microsoft.Agents.AI.Workflows;
+
+            namespace TestNamespace;
+
+            public class FeedbackResult { }
+
+            [SendsMessage(typeof(FeedbackResult))]
+            [YieldsOutput(typeof(string))]
+            public partial class FeedbackExecutor : Executor<string>
+            {
+                public FeedbackExecutor() : base("feedback") { }
+
+                public override System.Threading.Tasks.ValueTask HandleAsync(string message, IWorkflowContext context, System.Threading.CancellationToken cancellationToken = default)
+                    => default;
+            }
+            """;
+
+        var result = GeneratorTestHelper.RunGenerator(source);
+
+        result.RunResult.GeneratedTrees.Should().HaveCount(1);
+        result.RunResult.Diagnostics.Should().BeEmpty();
+
+        var generated = result.RunResult.GeneratedTrees[0].ToString();
+
+        // Base class Executor<T> overrides ConfigureProtocol, so the generated override
+        // must chain to base to preserve the inherited handler registration.
+        generated.Should().Contain("return base.ConfigureProtocol(protocolBuilder)",
+            because: "Executor<T> overrides ConfigureProtocol, so base must be called to preserve its handler registration");
+        generated.Should().Contain(".SendsMessage<global::TestNamespace.FeedbackResult>()");
+        generated.Should().Contain(".YieldsOutput<string>()");
+    }
+
+    [Fact]
+    public void ProtocolOnly_DerivesDirectlyFromExecutor_DoesNotGenerateBaseCall()
+    {
+        // A protocol-only partial executor deriving directly from Executor (abstract base
+        // with no non-abstract ConfigureProtocol override) should generate "return protocolBuilder"
+        // rather than "return base.ConfigureProtocol(protocolBuilder)".
+        var source = """
+            using System;
+            using System.Threading;
+            using System.Threading.Tasks;
+            using Microsoft.Agents.AI.Workflows;
+
+            namespace TestNamespace;
+
+            public class BroadcastMessage { }
+
+            [SendsMessage(typeof(BroadcastMessage))]
+            public partial class BroadcastExecutor : Executor
+            {
+                public BroadcastExecutor() : base("broadcast") { }
+            }
+            """;
+
+        var result = GeneratorTestHelper.RunGenerator(source);
+
+        result.RunResult.GeneratedTrees.Should().HaveCount(1);
+        result.RunResult.Diagnostics.Should().BeEmpty();
+
+        var generated = result.RunResult.GeneratedTrees[0].ToString();
+
+        // Executor's ConfigureProtocol is abstract — no base call needed.
+        generated.Should().Contain("return protocolBuilder",
+            because: "Executor base class has no non-abstract ConfigureProtocol, so no base call is needed");
+        generated.Should().NotContain("base.ConfigureProtocol");
+    }
+
     #endregion
 
     #region Generic Executor Tests