Saga identity from attribute

src/Testing/CoreTests/Persistence/Sagas/saga_id_member_determination.cs

@@ -12,18 +12,29 @@ public class saga_id_member_determination
     [InlineData(typeof(SomeSagaMessage4), nameof(SomeSagaMessage4.Id))]
     public void determine_the_member(Type messageType, string expectedMemberName)
     {
-        SagaChain.DetermineSagaIdMember(messageType, typeof(SomeSaga)).Name
+        SagaChain.DetermineSagaIdMember(messageType, typeof(SomeSaga))?.Name
             .ShouldBe(expectedMemberName);
     }
+
+    [Fact]
+    public void member_is_determined_by_attribute()
+    {
+        var method = typeof(SomeSaga).GetMethod(nameof(SomeSaga.Handle));
+
+        SagaChain.DetermineSagaIdMember(typeof(SomeSagaMessage5), typeof(SomeSaga), method)
+            !.Name.ShouldBe(nameof(SomeSagaMessage5.Hello));
+    }
 }
 
-public record SomeSagaMessage1(Guid Id, [property: SagaIdentity]Guid RandomName);
+public record SomeSagaMessage1(Guid Id, [property: SagaIdentity] Guid RandomName);
 public record SomeSagaMessage2(Guid SagaId, Guid Id);
 public record SomeSagaMessage3(Guid Id, Guid SomeSagaId, Guid SagaId);
 public record SomeSagaMessage4(Guid Id);
-
+public record SomeSagaMessage5(Guid Hello, Guid Id, Guid SagaId, Guid SomeSagaId);
 
 public class SomeSaga
 {
     public Guid Id { get; set; }
+
+    public void Handle([SagaIdentityFrom(nameof(SomeSagaMessage5.Hello))] SomeSagaMessage5 message) { }
 }

src/Wolverine/Persistence/Sagas/SagaChain.cs

@@ -1,12 +1,11 @@
-using System.Reflection;
 using JasperFx;
 using JasperFx.CodeGeneration;
 using JasperFx.CodeGeneration.Frames;
 using JasperFx.CodeGeneration.Model;
 using JasperFx.Core;
 using JasperFx.Core.Reflection;
+using System.Reflection;
 using Wolverine.Logging;
-using Wolverine.Runtime;
 using Wolverine.Runtime.Handlers;
 
 namespace Wolverine.Persistence.Sagas;
@@ -29,8 +28,17 @@ public SagaChain(WolverineOptions options, IGrouping<Type, HandlerCall> grouping
     {
         try
         {
-            SagaType = grouping.Where(x => x.HandlerType.CanBeCastTo<Saga>()).Select(x => x.HandlerType)
-                .Distinct().Single();
+            var saga = grouping.Where(x => x.HandlerType.CanBeCastTo<Saga>()).DistinctBy(x => x.HandlerType).Single();
+            SagaType = saga.HandlerType;
+            SagaMethodInfo = saga.Method;
+
+            SagaIdMember = DetermineSagaIdMember(MessageType, SagaType, saga.Method);
+
+            // Automatically audit the saga id
+            if (SagaIdMember != null && AuditedMembers.All(x => x.Member != SagaIdMember))
+            {
+                AuditedMembers.Add(new AuditedMember(SagaIdMember, SagaIdMember.Name, SagaIdMember.Name));
+            }
         }
         catch (Exception e)
         {
@@ -41,14 +49,6 @@ public SagaChain(WolverineOptions options, IGrouping<Type, HandlerCall> grouping
                 $"Command types cannot be handled by multiple saga types. Message {MessageType.FullNameInCode()} is handled by sagas {handlerTypes}",
                 e);
         }
-
-        SagaIdMember = DetermineSagaIdMember(MessageType, SagaType);
-
-        // Automatically audit the saga id
-        if (SagaIdMember != null && AuditedMembers.All(x => x.Member != SagaIdMember))
-        {
-            AuditedMembers.Add(new AuditedMember(SagaIdMember, SagaIdMember.Name, SagaIdMember.Name));
-        }
     }
 
     public override bool TryInferMessageIdentity(out PropertyInfo? property)
@@ -69,6 +69,8 @@ protected override void tryAssignStickyEndpoints(HandlerCall handlerCall, Wolver
 
     public Type SagaType { get; }
 
+    public MethodInfo? SagaMethodInfo { get; set; }
+
     public MemberInfo? SagaIdMember { get; set; }
 
     public MethodCall[] ExistingCalls { get; set; } = [];
@@ -77,13 +79,18 @@ protected override void tryAssignStickyEndpoints(HandlerCall handlerCall, Wolver
 
     public MethodCall[] NotFoundCalls { get; set; } = [];
 
-    public static MemberInfo? DetermineSagaIdMember(Type messageType, Type sagaType)
+    public static MemberInfo? DetermineSagaIdMember(Type messageType, Type sagaType, MethodInfo? sagaHandlerMethod = null)
     {
         var expectedSagaIdName = $"{sagaType.Name}Id";
 
+        var specifiedSagaIdMemberName = sagaHandlerMethod?.GetParameters()
+            .Select(x => x.GetCustomAttribute<SagaIdentityFromAttribute>())
+            .FirstOrDefault(a => a != null)?.PropertyName;
+
         var members = messageType.GetFields().OfType<MemberInfo>().Concat(messageType.GetProperties()).ToArray();
         return members.FirstOrDefault(x => x.HasAttribute<SagaIdentityAttribute>())
-               ?? members.FirstOrDefault(x => x.Name == expectedSagaIdName)
+               ?? members.FirstOrDefault(x => x.Name == (specifiedSagaIdMemberName ?? expectedSagaIdName))
+               ?? members.FirstOrDefault(x => x.Name == expectedSagaIdName.Replace("Saga", "", StringComparison.InvariantCultureIgnoreCase))
                ?? members.FirstOrDefault(x => x.Name == SagaIdMemberName) ??
                members.FirstOrDefault(x => x.Name.EqualsIgnoreCase("Id"));
     }
@@ -97,14 +104,14 @@ internal override List<Frame> DetermineFrames(GenerationRules rules, IServiceCon
         MessageVariable messageVariable)
     {
         applyCustomizations(rules, container);
-        
+
         if (AuditedMembers.Count != 0)
         {
             Middleware.Insert(0, new AuditToActivityFrame(this));
         }
 
         var frameProvider = rules.GetPersistenceProviders(this, container);
-        
+
         frameProvider.ApplyTransactionSupport(this, container);
 
         NotFoundCalls = findByNames(NotFound);
@@ -133,7 +140,7 @@ internal override List<Frame> DetermineFrames(GenerationRules rules, IServiceCon
             generateCodeForMaybeExisting(container, frameProvider, list);
         }
 
-// .Concat(handlerReturnValueFrames)
+        // .Concat(handlerReturnValueFrames)
 
         return Middleware.Concat(container.TryCreateConstructorFrames(Handlers)).Concat(list).Concat(Postprocessors).ToList();
     }
@@ -185,7 +192,7 @@ private void generateForOnlyStartingSaga(IServiceContainer container, IPersisten
         {
             return;
         }
-        
+
         var ifNotCompleted = buildFrameForConditionalInsert(sagaVariable, frameProvider, container);
         frames.Add(ifNotCompleted);
     }

src/Wolverine/Persistence/Sagas/SagaIdentityFromAttribute.cs

@@ -0,0 +1,10 @@
+namespace Wolverine.Persistence.Sagas;
+
+/// <summary>
+///     Marks a public property on a message type handler parameter as the saga state identity
+/// </summary>
+[AttributeUsage(AttributeTargets.Parameter)]
+public class SagaIdentityFromAttribute(string propertyName) : Attribute
+{
+    public string PropertyName { get => propertyName; }
+}