Use generated saga correlation accessors and emit finder-only sagas

src/NServiceBus.Core.Analyzer.Tests.Roslyn5/ApprovalFiles/AddSagaGeneratorTests.FinderOnlySagas.approved.txt

@@ -0,0 +1,172 @@
+// == NServiceBus.Core.Analyzer/NServiceBus.Core.Analyzer.Sagas.AddSagaGenerator/HandlerRegistrations.Sagas.g.cs =======
+// <auto-generated/>
+
+#nullable enable annotations
+#nullable disable warnings
+
+// Suppress warnings about [Obsolete] member usage in generated code.
+#pragma warning disable CS0612, CS0618
+
+namespace NServiceBus
+{
+    public static partial class FinderOnlySagasHandlerRegistryExtensions
+    {
+        public sealed partial class FinderOnlySagasRootRegistry
+        {
+            public sealed partial class FinderOnlyRegistry
+            {
+                partial void AddAllSagasCore()
+                {
+                    AddFinderOnlySaga();
+                }
+
+                /// <summary>
+                /// Registers the <see cref="global::FinderOnly.FinderOnlySaga"/> saga with the endpoint configuration.
+                /// </summary>
+                public void AddFinderOnlySaga()
+                {
+                    var sagaMetadataCollection = NServiceBus.Configuration.AdvancedExtensibility.AdvancedExtensibilityExtensions.GetSettings(_configuration)
+                       .GetOrCreate<NServiceBus.Sagas.SagaMetadataCollection>();
+                    var associatedMessages = new NServiceBus.Sagas.SagaMessage[]
+                    {
+                        new NServiceBus.Sagas.SagaMessage(typeof(global::FinderOnly.StartSagaMessage), true, false),
+                    };
+                    NServiceBus.Sagas.MessagePropertyAccessor[] propertyAccessors = [
+                    ];
+                    var metadata = NServiceBus.Sagas.SagaMetadata.Create<global::FinderOnly.FinderOnlySaga, global::FinderOnly.FinderOnlySagaData>(associatedMessages, null, propertyAccessors);
+                    sagaMetadataCollection.Add(metadata);
+
+                    var settings = NServiceBus.Configuration.AdvancedExtensibility.AdvancedExtensibilityExtensions.GetSettings(_configuration);
+                    var messageHandlerRegistry = settings.GetOrCreate<NServiceBus.Unicast.MessageHandlerRegistry>();
+                    var messageMetadataRegistry = settings.GetOrCreate<NServiceBus.Unicast.Messages.MessageMetadataRegistry>();
+                    messageHandlerRegistry.AddMessageHandlerForMessage<global::FinderOnly.FinderOnlySaga, global::FinderOnly.StartSagaMessage>();
+                    messageMetadataRegistry.RegisterMessageTypeWithHierarchy(typeof(global::FinderOnly.StartSagaMessage), []);
+                }
+            }
+        }
+    }
+}
+
+// == NServiceBus.Core.Analyzer/NServiceBus.Core.Analyzer.AddHandlerAndSagasRegistrationGenerator/HandlerRegistrations.g.cs ==
+// <auto-generated/>
+
+#nullable enable annotations
+#nullable disable warnings
+
+// Suppress warnings about [Obsolete] member usage in generated code.
+#pragma warning disable CS0612, CS0618
+
+namespace NServiceBus
+{
+    /// <summary>
+    /// Provides access to handler and saga registries discovered in the <i>FinderOnlySagas</i> assembly.
+    /// </summary>
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("NService.Core.Analyzer.Tests", "1.0.0")]
+    public static partial class FinderOnlySagasHandlerRegistryExtensions
+    {
+        extension (global::NServiceBus.HandlerRegistry registry)
+        {
+            /// <summary>
+            /// Gets the root registry for handler and saga types in the <i>FinderOnlySagas</i> assembly.
+            /// </summary>
+            /// <remarks>
+            /// Use the returned registry to access namespace-specific registries and add-all methods for this assembly.
+            /// </remarks>
+            public FinderOnlySagasRootRegistry FinderOnlySagasAssembly => new(registry.Configuration);
+        }
+
+        /// <summary>
+        /// Root registry to add handlers and sagas for the entire assembly.
+        /// </summary>
+        public sealed partial class FinderOnlySagasRootRegistry(global::NServiceBus.EndpointConfiguration configuration)
+        {
+            readonly global::NServiceBus.EndpointConfiguration _configuration = configuration ?? throw new System.ArgumentNullException(nameof(configuration));
+
+            /// <summary>
+            /// Gets the registry for the <i>FinderOnly</i> namespace segment under this branch.
+            /// </summary>
+            public FinderOnlyRegistry FinderOnly => new(_configuration);
+
+            /// <summary>
+            /// Registers all handlers and sagas for this namespace segment and its child namespaces.
+            /// </summary>
+            /// <remarks>
+            /// Includes child registries: <see cref="FinderOnly"/>.
+            /// </remarks>
+            public void AddAll()
+            {
+                AddAllHandlers();
+                AddAllSagas();
+            }
+
+            /// <summary>
+            /// Registers all handlers for this namespace segment and its child namespaces.
+            /// </summary>
+            /// <remarks>
+            /// Includes child registries: <see cref="FinderOnly"/>.
+            /// </remarks>
+            public void AddAllHandlers()
+            {
+                AddAllHandlersCore();
+                FinderOnly.AddAllHandlers();
+            }
+
+            /// <summary>
+            /// Registers all sagas for this namespace segment and its child namespaces.
+            /// </summary>
+            /// <remarks>
+            /// Includes child registries: <see cref="FinderOnly"/>.
+            /// </remarks>
+            public void AddAllSagas()
+            {
+                AddAllSagasCore();
+                FinderOnly.AddAllSagas();
+            }
+
+            partial void AddAllHandlersCore();
+            partial void AddAllSagasCore();
+
+            /// <summary>
+            /// Registry for the <i>FinderOnly</i> namespace segment. Use this registry to add handlers and sagas for this branch.
+            /// </summary>
+            public sealed partial class FinderOnlyRegistry(global::NServiceBus.EndpointConfiguration configuration)
+            {
+                readonly global::NServiceBus.EndpointConfiguration _configuration = configuration ?? throw new System.ArgumentNullException(nameof(configuration));
+
+                /// <summary>
+                /// Registers all handlers and sagas for this namespace segment and its child namespaces.
+                /// </summary>
+                /// <remarks>
+                /// Includes sagas in this namespace: <see cref="AddFinderOnlySaga"/>.
+                /// </remarks>
+                public void AddAll()
+                {
+                    AddAllHandlers();
+                    AddAllSagas();
+                }
+
+                /// <summary>
+                /// Registers all handlers for this namespace segment and its child namespaces.
+                /// </summary>
+                public void AddAllHandlers()
+                {
+                    AddAllHandlersCore();
+                }
+
+                /// <summary>
+                /// Registers all sagas for this namespace segment and its child namespaces.
+                /// </summary>
+                /// <remarks>
+                /// Includes sagas in this namespace: <see cref="AddFinderOnlySaga"/>.
+                /// </remarks>
+                public void AddAllSagas()
+                {
+                    AddAllSagasCore();
+                }
+
+                partial void AddAllHandlersCore();
+                partial void AddAllSagasCore();
+            }
+        }
+    }
+}

src/NServiceBus.Core.Analyzer.Tests.Roslyn5/Sagas/AddSagaGeneratorTests.cs

@@ -7,6 +7,61 @@
 [TestFixture]
 public class AddSagaGeneratorTests
 {
+    [Test]
+    public void FinderOnlySagas()
+    {
+        var source = """
+                     using System.Threading;
+                     using System.Threading.Tasks;
+                     using NServiceBus;
+                     using NServiceBus.Persistence;
+                     using NServiceBus.Extensibility;
+                     using NServiceBus.Sagas;
+
+                     public class Test
+                     {
+                         public void Configure(EndpointConfiguration cfg)
+                         {
+                             cfg.Handlers.FinderOnlySagasAssembly.AddAll();
+                         }
+                     }
+
+                     namespace FinderOnly
+                     {
+                         [Saga]
+                         public class FinderOnlySaga : Saga<FinderOnlySagaData>,
+                             IAmStartedByMessages<StartSagaMessage>
+                         {
+                             protected override void ConfigureHowToFindSaga(SagaPropertyMapper<FinderOnlySagaData> mapper)
+                             {
+                                 mapper.ConfigureFinderMapping<StartSagaMessage, FinderOnlyFinder>();
+                             }
+
+                             public Task Handle(StartSagaMessage message, IMessageHandlerContext context) => Task.CompletedTask;
+                         }
+
+                         public class FinderOnlySagaData : ContainSagaData
+                         {
+                             public string Property { get; set; }
+                         }
+
+                         public class FinderOnlyFinder : ISagaFinder<FinderOnlySagaData, StartSagaMessage>
+                         {
+                             public Task<FinderOnlySagaData> FindBy(StartSagaMessage message, ISynchronizedStorageSession storageSession, IReadOnlyContextBag context, CancellationToken cancellationToken = default) => Task.FromResult(default(FinderOnlySagaData));
+                         }
+
+                         public class StartSagaMessage : IMessage;
+                     }
+                     """;
+
+        SourceGeneratorTest.ForIncrementalGenerator<AddSagaGenerator>()
+            .WithIncrementalGenerator<AddHandlerAndSagasRegistrationGenerator>()
+            .WithSource(source, "test.cs")
+            .Run()
+            .Approve()
+            .AssertRunsAreEqual();
+    }
+
     [Test]
     public void BasicSagas()
     {

src/NServiceBus.Core.Analyzer.Tests.Roslyn5/Sagas/AddSagaInterceptorSuppressorTests.cs

@@ -57,6 +57,60 @@ public class SampleCommand : ICommand
         Assert.That(diagnostics, Does.Not.Contain("IL2026"));
     }
 
+    [Test]
+    public void SuppressesIL2026ForFinderOnlySaga()
+    {
+        var source = """
+                     using System.Threading;
+                     using System.Threading.Tasks;
+                     using NServiceBus;
+                     using NServiceBus.Persistence;
+                     using NServiceBus.Extensibility;
+                     using NServiceBus.Sagas;
+
+                     public class Test
+                     {
+                         public void Configure(EndpointConfiguration cfg)
+                         {
+                             cfg.AddSaga<FinderOnlySaga>();
+                         }
+                     }
+
+                     public class FinderOnlySaga : Saga<FinderOnlySagaData>,
+                         IAmStartedByMessages<StartSagaMessage>
+                     {
+                         protected override void ConfigureHowToFindSaga(SagaPropertyMapper<FinderOnlySagaData> mapper)
+                         {
+                             mapper.ConfigureFinderMapping<StartSagaMessage, FinderOnlyFinder>();
+                         }
+
+                         public Task Handle(StartSagaMessage message, IMessageHandlerContext context) => Task.CompletedTask;
+                     }
+
+                     public class FinderOnlySagaData : ContainSagaData
+                     {
+                         public string Property { get; set; }
+                     }
+
+                     public class FinderOnlyFinder : ISagaFinder<FinderOnlySagaData, StartSagaMessage>
+                     {
+                         public Task<FinderOnlySagaData> FindBy(StartSagaMessage message, ISynchronizedStorageSession storageSession, IReadOnlyContextBag context, CancellationToken cancellationToken = default) => Task.FromResult(default(FinderOnlySagaData));
+                     }
+
+                     public class StartSagaMessage : IMessage;
+                     """;
+
+        var result = SourceGeneratorTest.ForIncrementalGenerator<AddSagaInterceptor>()
+            .WithSource(source, "test.cs")
+            .WithAnalyzer<MockTrimmingAnalyzer>()
+            .WithSuppressor<AddSagaInterceptorSuppressor>()
+            .Run();
+
+        var diagnostics = result.GetCompilationOutput();
+
+        Assert.That(diagnostics, Does.Not.Contain("IL2026"));
+    }
+
     [Test]
     public void DoesNotSuppressIL2026ForNonAddSagaCalls()
     {

src/NServiceBus.Core.Analyzer/Sagas/AddSagaInterceptor.Suppressor.cs

@@ -1,6 +1,7 @@
 namespace NServiceBus.Core.Analyzer.Sagas;
 
 using System.Collections.Immutable;
+using NServiceBus.Core.Analyzer.Handlers;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -45,10 +46,22 @@ public override void ReportSuppressions(SuppressionAnalysisContext context)
 
             var semanticModel = context.GetSemanticModel(sourceTree);
             var operation = semanticModel.GetOperation(node, context.CancellationToken);
-            if (operation is IInvocationOperation { TargetMethod: { } methodSymbol } && AddSagaInterceptor.Parser.IsAddSagaMethod(methodSymbol))
+            if (operation is not IInvocationOperation { TargetMethod: { } methodSymbol } || !AddSagaInterceptor.Parser.IsAddSagaMethod(methodSymbol))
             {
-                context.ReportSuppression(Suppression.Create(SuppressRUCDiagnostic, diagnostic));
+                continue;
+            }
+
+            // Only suppress when an interceptor can actually be emitted for this call site. A saga that cannot be
+            // parsed (no Saga<TSagaData> base, abstract, or otherwise unsupported) keeps the RequiresUnreferencedCode
+            // fallback warning.
+            if (methodSymbol.TypeArguments[0] is not INamedTypeSymbol sagaType ||
+                !HandlerKnownTypes.TryGet(context.Compilation, out var knownTypes) ||
+                Sagas.Parser.Parse(semanticModel, sagaType, knownTypes, context.CancellationToken) is null)
+            {
+                continue;
             }
+
+            context.ReportSuppression(Suppression.Create(SuppressRUCDiagnostic, diagnostic));
         }
     }
 

src/NServiceBus.Core.Analyzer/Sagas/Sagas.Emitter.cs

@@ -48,11 +48,13 @@ static void EmitSagaMetadataAdd(SourceWriter sourceWriter, SagaSpec details)
                 sourceWriter.WriteLine($"{propertyAccessorClassName}.Instance,");
             }
 
-            var correlationPropertyAccessorClassName = CorrelationPropertyAccessorName(details.SagaDataFullyQualifiedName, details.CorrelationPropertyMapping);
-            var correlationPropertyAccessor = $"{correlationPropertyAccessorClassName}.Instance";
-
             sourceWriter.Indentation--;
             sourceWriter.WriteLine("];");
+
+            // Finder-only sagas have no correlation property and therefore no generated correlation accessor.
+            var correlationPropertyAccessor = details.CorrelationPropertyMapping is { } correlationProperty
+                ? $"{CorrelationPropertyAccessorName(details.SagaDataFullyQualifiedName, correlationProperty)}.Instance"
+                : "null";
             sourceWriter.WriteLine($"var metadata = NServiceBus.Sagas.SagaMetadata.Create<{details.FullyQualifiedName}, {details.SagaDataFullyQualifiedName}>(associatedMessages, {correlationPropertyAccessor}, propertyAccessors);");
             sourceWriter.WriteLine("sagaMetadataCollection.Add(metadata);");
         }
@@ -137,7 +139,11 @@ static void EmitCorrelationPropertyAccessors(SourceWriter sourceWriter, Immutabl
             var uniqueMappings = new Dictionary<(string SagaDataType, string PropertyType, string PropertyName), (CorrelationPropertyMappingSpec Mapping, string SagaDataType)>();
             foreach (var saga in sagas)
             {
-                var mapping = saga.CorrelationPropertyMapping;
+                if (saga.CorrelationPropertyMapping is not { } mapping)
+                {
+                    continue;
+                }
+
                 var key = (saga.SagaDataFullyQualifiedName, mapping.PropertyType, mapping.PropertyName);
                 if (!uniqueMappings.ContainsKey(key))
                 {

src/NServiceBus.Core.Analyzer/Sagas/Sagas.Parser.cs

@@ -18,7 +18,7 @@ public static partial class Sagas
 
     public record SagaSpec : AddHandlerAndSagasRegistrationGenerator.Parser.BaseSpec
     {
-        public SagaSpec(HandlerSpec handler, string sagaDataFullyQualifiedName, CorrelationPropertyMappingSpec correlationProperty, ImmutableEquatableArray<PropertyMappingSpec> propertyMappings)
+        public SagaSpec(HandlerSpec handler, string sagaDataFullyQualifiedName, CorrelationPropertyMappingSpec? correlationProperty, ImmutableEquatableArray<PropertyMappingSpec> propertyMappings)
             : base(handler)
         {
             SagaDataFullyQualifiedName = sagaDataFullyQualifiedName;
@@ -29,7 +29,7 @@ public SagaSpec(HandlerSpec handler, string sagaDataFullyQualifiedName, Correlat
 
         public string SagaDataFullyQualifiedName { get; }
 
-        public CorrelationPropertyMappingSpec CorrelationPropertyMapping { get; }
+        public CorrelationPropertyMappingSpec? CorrelationPropertyMapping { get; }
         public ImmutableEquatableArray<PropertyMappingSpec> PropertyMappings { get; }
         public HandlerSpec Handler { get; }
     }
@@ -60,10 +60,11 @@ public static class Parser
             var sagaBaseSpec = Handlers.Parser.Parse(sagaType, BaseParser.SpecKind.Saga, knownTypes, cancellationToken);
             var sagaDataFullyQualifiedName = sagaDataType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
 
-            // Analyze ConfigureHowToFindSaga to extract mappings
+            // Analyze ConfigureHowToFindSaga to extract mappings. Finder-only sagas have no correlation property
+            // and no property mappings but are still valid sagas that must be registered.
             var (correlationProperty, propertyMappings) = ExtractPropertyMappings(sagaType, sagaSemanticModel, cancellationToken);
 
-            return correlationProperty is null ? null : new SagaSpec(sagaBaseSpec, sagaDataFullyQualifiedName, correlationProperty.Value, propertyMappings);
+            return new SagaSpec(sagaBaseSpec, sagaDataFullyQualifiedName, correlationProperty, propertyMappings);
         }
 
         static INamedTypeSymbol? GetSagaDataType(INamedTypeSymbol sagaType)