Accessing the implementation of INuGetPackageInstaller

[ap0llo]

Hi,

I'm currently working on a module that provides a custom implementation of IPackageInstaller.
My implementation is supposed to be a wrapper around the NuGet package installer (NuGetPackageInstaller from Cake.NuGet).

Since NuGetPackageInstaller is internal but implements INuGetPackageInstaller, I declared a dependency to INuGetPackageInstaller by adding a constructor parameter and expected that the DI container would be able to resolve the dependency.

My code looks something like this (I reduced it to the bare minimum to show the issue):

public class MyCustomPackageInstaller
{
    public MyCustomPackageInstaller(INuGetPackageInstaller nugetPackageInstaller)
    { } 
}

public class MyModule : ICakeModule
{
    public void Register(ICakeContainerRegistrar registrar)
    {
        registrar.RegisterType<MyCustomPackageInstaller>().As<IPackageInstaller>().Singleton();
    }
}

I'm loading both modules in the my project's Main():

return new CakeHost()
    .UseModule<NuGetModule>()
    .UseModule<MyModule>()
    .Run(args);

In NuGetModule.cs, I found the correct registration

registrar.RegisterType<NuGetPackageInstaller>().As<INuGetPackageInstaller>().As<IPackageInstaller>().Singleton();

I expected this to work but get an error indicating that INuGetPackageInstaller cannot be resolved.

I assume it has something to do with the two calls to As<T>() which seems to only register the type as IPackageInstaller.
If I pull the internal type out of Cake.NuGet and explicitly register it in my module, it could get it to work:

var implementationType = typeof(INuGetPackageInstaller).Assembly.GetTypes().Single(x => x.FullName == "Cake.NuGet.NuGetPackageInstaller");
registrar.RegisterType(implementationType).As<INuGetPackageInstaller>().Singleton();

Obviously this is not a solution I want to keep, since I'm relying on internals of the Cake.NuGet package.

So my questions is, should the DI container be able to resolve INuGetPackageInstaller or is the current behaviour as intended?

[ap0llo]

I investigated a little further and it seems that there is a different between the scripting runner and Cake Frosting.
A implementation of INuGetPackageInstaller can be injected when loading the module in a Cake Scripting project, but not in a Frosting project.

As far as I can tell, the implementation of ICakeContainerRegistrar respectively ICakeRegistrationBuilder is different.

In a scripting project, calling As<T>() multiple times seems to add multiple services to the DI container, whereas in Cake Frosting, As<T>() overwrites the previous registration by just updating the ServiceType property:

cake/src/Cake.Frosting/Internal/ServiceRegistration.cs

Line 23 in 9828d7b

public ICakeRegistrationBuilder As(Type type)

public ICakeRegistrationBuilder As(Type type)
{
    ServiceType = type; // <- this discards the previous registration
    return this;
}