From 596d244beb56426d0d98415bd452f0321e233044 Mon Sep 17 00:00:00 2001
From: Chris Patterson <chris@phatboyg.com>
Date: Wed, 3 Apr 2024 15:17:13 -0500
Subject: [PATCH] Fixed #5015 - States and Events from state machine base
 classes are now properly initialized

---
 .../MassTransitStateMachine.cs                |  20 ++-
 .../SagaStateMachineTests/BaseClass_Specs.cs  | 123 ++++++++++++++++++
 2 files changed, 141 insertions(+), 2 deletions(-)
 create mode 100644 tests/MassTransit.Tests/SagaStateMachineTests/BaseClass_Specs.cs

diff --git a/src/MassTransit/SagaStateMachine/MassTransitStateMachine.cs b/src/MassTransit/SagaStateMachine/MassTransitStateMachine.cs
index 8b175afad7e..c5d97e548fc 100644
--- a/src/MassTransit/SagaStateMachine/MassTransitStateMachine.cs
+++ b/src/MassTransit/SagaStateMachine/MassTransitStateMachine.cs
@@ -1978,8 +1978,7 @@ IEnumerable<PropertyInfo> GetStateMachineProperties()
 
         bool TryGetBackingField(PropertyInfo property, out FieldInfo backingField)
         {
-            _backingFields ??= GetType()
-                .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
+            _backingFields ??= GetBackingFields(GetType())
                 .Where(field =>
                     field.Attributes.HasFlag(FieldAttributes.Private) &&
                     field.Attributes.HasFlag(FieldAttributes.InitOnly) &&
@@ -1997,6 +1996,23 @@ bool TryGetBackingField(PropertyInfo property, out FieldInfo backingField)
             return backingField != null;
         }
 
+        static IEnumerable<FieldInfo> GetBackingFields(Type type)
+        {
+            while (true)
+            {
+                foreach (var fieldInfo in type.GetFields(BindingFlags.NonPublic | BindingFlags.Instance))
+                    yield return fieldInfo;
+
+                if (type.BaseType == null)
+                    break;
+
+                if (type.BaseType.IsGenericType && type.BaseType.GetGenericTypeDefinition() == typeof(MassTransitStateMachine<>))
+                    break;
+
+                type = type.BaseType;
+            }
+        }
+
         void InitializeState(MassTransitStateMachine<TInstance> stateMachine, PropertyInfo property, StateMachineState state)
         {
             if (property.CanWrite)
diff --git a/tests/MassTransit.Tests/SagaStateMachineTests/BaseClass_Specs.cs b/tests/MassTransit.Tests/SagaStateMachineTests/BaseClass_Specs.cs
new file mode 100644
index 00000000000..fcd10695a7e
--- /dev/null
+++ b/tests/MassTransit.Tests/SagaStateMachineTests/BaseClass_Specs.cs
@@ -0,0 +1,123 @@
+namespace MassTransit.Tests.SagaStateMachineTests
+{
+    using System.Threading.Tasks;
+    using BaseStateMachineTestSubjects;
+    using MassTransit.Testing;
+    using Microsoft.Extensions.DependencyInjection;
+    using NUnit.Framework;
+
+
+    [TestFixture]
+    public class Using_a_base_state_machine
+    {
+        [Test]
+        public async Task Should_initialize_all_states_and_events()
+        {
+            await using var provider = new ServiceCollection()
+                .AddMassTransitTestHarness(x =>
+                {
+                    x.AddSagaStateMachine<HappyGoLuckyStateMachine, HappyGoLuckyState>();
+                })
+                .BuildServiceProvider(true);
+
+            var harness = await provider.StartTestHarness();
+
+            var id = NewId.NextGuid();
+
+            await harness.Bus.Publish(new HappyEvent(id));
+
+            Assert.That(await harness.Consumed.Any<HappyEvent>());
+
+            await harness.Bus.Publish(new EndItAllEvent(id));
+
+            Assert.That(await harness.Consumed.Any<EndItAllEvent>());
+        }
+    }
+
+
+    namespace BaseStateMachineTestSubjects
+    {
+        using System;
+
+
+        public class HappyEvent
+        {
+            public HappyEvent(Guid correlationId)
+            {
+                CorrelationId = correlationId;
+            }
+
+            public Guid CorrelationId { get; set; }
+        }
+
+
+        public class GoLuckyEvent
+        {
+            public GoLuckyEvent(Guid correlationId)
+            {
+                CorrelationId = correlationId;
+            }
+
+            public Guid CorrelationId { get; set; }
+        }
+
+
+        public class EndItAllEvent
+        {
+            public EndItAllEvent(Guid correlationId)
+            {
+                CorrelationId = correlationId;
+            }
+
+            public Guid CorrelationId { get; set; }
+        }
+
+
+        public class CommonStateMachine<T> :
+            MassTransitStateMachine<T>
+            where T : class, SagaStateMachineInstance
+        {
+            //
+            // ReSharper disable UnassignedGetOnlyAutoProperty
+            public State Happy { get; }
+            public State GoLucky { get; }
+
+            public Event<HappyEvent> OnHappy { get; }
+            public Event<GoLuckyEvent> OnGoLucky { get; }
+        }
+
+
+        public class HappyGoLuckyState :
+            SagaStateMachineInstance
+        {
+            public string CurrentState { get; set; }
+            public Guid CorrelationId { get; set; }
+        }
+
+
+        public class HappyGoLuckyStateMachine :
+            CommonStateMachine<HappyGoLuckyState>
+        {
+            public HappyGoLuckyStateMachine()
+            {
+                InstanceState(x => x.CurrentState);
+
+                Initially(
+                    When(OnHappy)
+                        .TransitionTo(Happy),
+                    When(OnGoLucky)
+                        .TransitionTo(GoLucky));
+
+                During(Happy, GoLucky,
+                    When(OnEndItAll)
+                        .TransitionTo(Finished));
+
+                SetCompletedWhenFinalized();
+            }
+
+            public State Finished { get; }
+
+            public Event<EndItAllEvent> OnEndItAll { get; }
+        }
+    }
+}