The AnyConcreteTypeNotAlreadyRegisteredSource throws an exception when tries to Resolve unregistered Meta<T> types

[nemesv]

If the AnyConcreteTypeNotAlreadyRegisteredSource is used then resolving any non registered Meta types throws an exception.

Here is some testcases demonstating the problem

    [TestFixture]
    public class AnyConcreteTypeNotAlreadyRegisteredSourceTest
    {
        public class ScreenAppender : ILogAppender { }
        public interface ILogAppender { }

        //passes
        [Test]
        public void Test()
        {
            var builder = new ContainerBuilder();
            builder.Register(c => new ScreenAppender())
                   .As<ILogAppender>()
                   .WithMetadata("AppenderName", "screen");
            builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource());
            var container = builder.Build();
            var meta = container.Resolve<IEnumerable<Meta<ILogAppender>>>();
            Assert.AreEqual(1, meta.Count());
        }

        //passes
        [Test]
        public void Test2()
        {
            var builder = new ContainerBuilder();
            var container = builder.Build();
            var meta = container.Resolve<IEnumerable<Meta<ILogAppender>>>();
            Assert.AreEqual(0, meta.Count());
        }

        //fails
        [Test]
        public void Test3()
        {
            var builder = new ContainerBuilder();
            builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource());
            var container = builder.Build();
            var meta = container.Resolve<IEnumerable<Meta<ILogAppender>>>();
            Assert.AreEqual(1, meta.Count());
        }
    }

The thrid test throws the following exeption

Autofac.Core.DependencyResolutionException : None of the constructors found with 'Public binding flags' on type Autofac.Features.Metadata.Meta1[ClassLibrary.AnyConcreteTypeNotAlreadyRegisteredSourceTest+ILogAppender]
can be invoked with the available services and parameters:
Cannot resolve parameter 'ILogAppender value' of constructor 'Void .ctor(ILogAppender, System.Collections.Generic.IDictionary`2[System.String,System.Object])'.

See this question on SO for more context : http://stackoverflow.com/questions/21743262/autofac-mvc-5-registerwebapifilterprovider-causes-unresolveable-ioverridefilter

[tillig]

This appears to affect all generated relationship sources - Owned<T>, Meta<T>, and Lazy<T> are all affected. It looks like Func<T> gets ignored by virtue of it being a delegate (which we already check for and reject in ACTNARS).

An ideal solution would not hardcode all the relationships in ACTNARS but would instead somehow not provide stuff that's already provided. Hmmm.

[tillig]

It's almost like the registration lookup process needs to behave like an event, like when a lookup takes place in a registration source, not only would you return a (potentially empty) list of registrations, but also something to indicate "stop processing, it's been handled." That way the MetaRegistrationSource or other sources would be able to say, "I'm the system of record for Meta<T> and there is no registration for the thing you asked for, full stop."

I'll have to think about how to deal with that. In the meantime, I'll add the unit test (skipped for now) to the repo so we can work through it.

[tillig]

OK, I think I figured it out.

For generic types we need to not only check to see if the whole generic is registered, but also see if we can handle the thing in the generic. I'm working through tests now.

That said, I think the bottom test will still fail:

        [Test]
        public void Test3()
        {
            var builder = new ContainerBuilder();
            builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource());
            var container = builder.Build();
            var meta = container.Resolve<IEnumerable<Meta<ILogAppender>>>();
            Assert.AreEqual(1, meta.Count());
        }

If no ILogAppender is registered, you won't get any elements back in the IEnumerable<Meta<ILogAppender>> resolution. ACTNARS doesn't search for concrete types that implement ILogger, it just creates concrete types. So IEnumerable<Meta<ScreenAppender>> would get you a single element back, but IEnumerable<Meta<ILogAppender>> would not.

Here's a test I have passing with the updated code:

       [Fact]
        public void DoesNotInterfereWithMetadata()
        {
            // Issue #495: Meta<T> not correctly handled with ACTNARS.
            var cb = new ContainerBuilder();
            cb.RegisterType<RegisteredType>().WithMetadata("value", 1);
            cb.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource());
            var container = cb.Build();

            var regType = container.Resolve<Meta<RegisteredType>>();
            Assert.Equal(1, regType.Metadata["value"]);

            var nonRegType = container.Resolve<Meta<NotRegisteredType>>();
            Assert.False(nonRegType.Metadata.ContainsKey("value"));

            var interfaceMeta = container.Resolve<IEnumerable<Meta<IInterfaceType>>>();
            Assert.Equal(0, interfaceMeta.Count());

            var classMeta = container.Resolve<IEnumerable<Meta<NotRegisteredType>>>();
            Assert.Equal(1, classMeta.Count());
        }

[tillig]

The fix for this is in v4.2.0-354 on the MyGet feed and will eventually be pushed to NuGet as 4.2.0.

[nemesv]

Cool! Thanks for the fix!

[tillig]

Published as 4.2.0 to NuGet.