Fix a bug in the original #1102 fix, which incorrectly relied on the target component's first service being unique to that component

Author: nblumhardt

src/Autofac/RegistrationExtensions.cs

@@ -69,6 +69,11 @@ public static IRegistrationBuilder<T, SimpleActivatorData, SingleRegistrationSty
 
         rb.SingleInstance();
 
+        // https://github.com/autofac/Autofac/issues/1102
+        // Single instance registrations with any custom activation phases (i.e. activation handlers) need to be auto-activated,
+        // so that other behavior (such as OnRelease) that expects 'normal' object lifetime behavior works as expected.
+        rb.RegistrationData.AddService(new AutoActivateService());
+
         rb.RegistrationData.DeferredCallback = builder.RegisterCallback(cr =>
         {
             if (rb.RegistrationData.Lifetime is not RootScopeLifetime ||
@@ -79,21 +84,6 @@ public static IRegistrationBuilder<T, SimpleActivatorData, SingleRegistrationSty
 
             activator.DisposeInstance = rb.RegistrationData.Ownership == InstanceOwnership.OwnedByLifetimeScope;
 
-            // https://github.com/autofac/Autofac/issues/1102
-            // Single instance registrations with any custom activation phases (i.e. activation handlers) need to be auto-activated,
-            // so that other behavior (such as OnRelease) that expects 'normal' object lifetime behavior works as expected.
-            if (rb.ResolvePipeline.Middleware.Any(s => s.Phase == PipelinePhase.Activation))
-            {
-                var autoStartService = rb.RegistrationData.Services.First();
-
-                var activationRegistration = new RegistrationBuilder<T, SimpleActivatorData, SingleRegistrationStyle>(
-                    new AutoActivateService(),
-                    new SimpleActivatorData(new DelegateActivator(typeof(T), (c, p) => c.ResolveService(autoStartService))),
-                    new SingleRegistrationStyle());
-
-                RegistrationBuilder.RegisterSingleComponent(cr, activationRegistration);
-            }
-
             RegistrationBuilder.RegisterSingleComponent(cr, rb);
         });
 

test/Autofac.Specification.Test/Features/StartableTests.cs

@@ -177,6 +177,17 @@ public void AutoActivate_DoesNotHideDefaultSelfService()
         Assert.True(container.IsRegistered<MyComponent2>());
     }
 
+    [Fact]
+    public void AutoActivate_RegisterInstanceActivationWorksWhenDefaultServiceOverloaded()
+    {
+        var instanceCount = 0;
+        var builder = new ContainerBuilder();
+        builder.RegisterInstance(new MyComponent2()).As<object>().OnActivated(_ => instanceCount++);
+        builder.RegisterType<object>();
+        builder.Build();
+        Assert.Equal(1, instanceCount);
+    }
+
     private class ComponentTakesStartableDependency : IStartable
     {
         public ComponentTakesStartableDependency(StartableTakesDependency dependency, bool expectStarted)