What is the difference between AddLamar() and UseLamar()?

I expected both of these tests to pass but the first one doesn’t. What am I missing?

[Fact]
public void ServiceCollection_AddLamar()
{
    var services = new ServiceCollection();
    services.AddLamar();
    var provider = services.BuildServiceProvider();

    using (var scope = provider.CreateScope())
    {
        Assert.IsType<Container>(scope);
    }
}

[Fact]
public void HostBuilder_UseLamar()
{
    var hostBuilder = new HostBuilder();
    hostBuilder.UseLamar();
    var host = hostBuilder.Build();

    using (var scope = host.Services.CreateScope())
    {
        Assert.IsType<Container>(scope);
    }
}

I can live with using HostBuilder but just don’t understand why the difference.

[jeremydmiller]

@RyanThomas73 You’re treading into “I take pull requests” territory here. I’m happy to take a PR if you want this, but nobody else is asking for this feature.

[RyanThomas73]

@jeremydmiller The point of being able to use the the BuildServiceProvider() is that the requirement of passing it into a lamar container constructor is misleading from an isolation / decoupling standpoint. Lamar’s service registry implements IServiceCollection but this is misleading, as the implementation can only be correctly used when combined with the lamar container.

IServiceCollection serviceCollection = SharedLibraryOrHelperToSetupDefaultServiceCollection();

// Working with an IServiceCollection here I would expect it to work as an IServiceCollection without 
// requiring the consumer of SharedLibraryOrHelperToSetupDefaultServiceCollection() to know or care
// that this service collection is implemented using Lamar and requires them to consume is a special way for it to work.
var serviceProvider = serviceCollection.BuildServiceProvider();