Decorators in flowing scope could cause stackoverflow exception. Fixes #998

Author: dotnetjunkie

src/SimpleInjector.Tests.Unit/FlowingScopeTests.cs

@@ -411,6 +411,19 @@ public void Scoped_instances_resolved_from_different_scopes_within_the_context_o
             Assert.AreNotSame(instance.Service1, instance.Service2);
         }
 
+        // #998
+        [TestMethod]
+        public void Verify_OnCollectionComponent_InjectedWithATransientDecorator_Succeeds()
+        {
+            var container = new Container();
+            container.Options.DefaultScopedLifestyle = ScopedLifestyle.Flowing;
+            container.Register<IPlugin, PluginImpl>();
+            container.RegisterDecorator<IPlugin, PluginDecorator>();
+            container.Collection.Register<IX>(typeof(XDependingOn<IPlugin>));
+            
+            container.Verify();
+        }
+
         public class ResolvingFromScopesInCtor<TService> where TService : class
         {
             public TService Service1 { get; }
@@ -444,5 +457,10 @@ public ScopedCommandHandlerProxy(Func<Scope, ICommandHandler<T>> decorateeFactor
                 this.DecorateeFactory = decorateeFactory;
             }
         }
+
+        public sealed class PluginDecorator : IPlugin
+        {
+            public PluginDecorator(IPlugin plugin) { }
+        }
     }
 }

src/SimpleInjector/InstanceProducer.cs

@@ -536,12 +536,20 @@ private static bool ContainsScopedComponentsInGraph(InstanceProducer producer)
                 producer.BuildExpression();
             }
 
-            return
-                producer.Lifestyle is SingletonLifestyle ? false :
-                producer.Lifestyle is ScopedLifestyle ? true :
-                producer.GetRelationships().Any(r => ContainsScopedComponentsInGraph(r.Dependency));
+            return ContainsScopedComponentsInGraphRecursive(producer);
         }
 
+        // We suppress building expressions for dependencies, because in the case of a decorator, the list of
+        // relationships will contain the decoratee, which will have its IsExpressionCreated set to false,
+        // even after BuildExpression() is called on the decorator. Calling BuildExpression on the decoratee
+        // will cause its producer to change and the decorator to be applied... again. This would cause the
+        // generation of an endless stream of new decorators and will lead to a stackoverflow exception.
+        // This is why BuildExpression is not called here.
+        private static bool ContainsScopedComponentsInGraphRecursive(InstanceProducer producer) => 
+            producer.Lifestyle is SingletonLifestyle ? false :
+            producer.Lifestyle is ScopedLifestyle ? true :
+            producer.GetRelationships().Any(r => ContainsScopedComponentsInGraphRecursive(r.Dependency));
+
         private Action<Scope>[] GetVerifiers()
         {
             lock (this.locker)