Resolve #916: IStartable that creates child lifetime scope during Start no longer tries to activate itself.

Author: tillig

src/Autofac/Core/Resolving/InstanceLookup.cs

@@ -96,14 +96,11 @@ private void StartStartableComponent(object instance)
                 && !ComponentRegistration.Metadata.ContainsKey(MetadataKeys.AutoActivated)
                 && ComponentRegistry.Properties.ContainsKey(MetadataKeys.StartOnActivatePropertyKey))
             {
-                try
-                {
-                    startable.Start();
-                }
-                finally
-                {
-                    ComponentRegistration.Metadata[MetadataKeys.AutoActivated] = true;
-                }
+                // Issue #916: Set the startable as "done starting" BEFORE calling Start
+                // so you don't get a StackOverflow if the component creates a child scope
+                // during Start. You don't want the startable trying to activate itself.
+                ComponentRegistration.Metadata[MetadataKeys.AutoActivated] = true;
+                startable.Start();
             }
         }
 

test/Autofac.Test/StartableTests.cs

@@ -51,6 +51,15 @@ public void WhenStartIsSpecified_StartableComponentsAreStarted()
             Assert.True(startable.StartCount > 0);
         }
 
+        [Fact]
+        public void WhenStartableCreatesChildScope_NoExceptionIsThrown()
+        {
+            // Issue #916
+            var builder = new ContainerBuilder();
+            builder.RegisterType<StartableCreatesLifetimeScope>().As<IStartable>().SingleInstance();
+            var container = builder.Build();
+        }
+
         [Theory]
         [InlineData(true)]
         [InlineData(false)]
@@ -139,6 +148,36 @@ public void Start()
             }
         }
 
+        // Issue #916
+        private class StartableCreatesLifetimeScope : IStartable
+        {
+            private readonly ILifetimeScope _scope;
+
+            public StartableCreatesLifetimeScope(ILifetimeScope scope)
+            {
+                this._scope = scope;
+            }
+
+            public void Start()
+            {
+                using (var nested = this._scope.BeginLifetimeScope("tag", b => { }))
+                {
+                }
+
+                using (var nested = this._scope.BeginLifetimeScope(b => { }))
+                {
+                }
+
+                using (var nested = this._scope.BeginLifetimeScope("tag"))
+                {
+                }
+
+                using (var nested = this._scope.BeginLifetimeScope())
+                {
+                }
+            }
+        }
+
         private class StartableDependency : IStartableDependency
         {
             private static int _count = 0;