[Feature] CommunityToolkit.Extensions.DependencyInjection package

[Sergio0694]

We built a source generator (with analyzers) to help with dependency injection registration in the Microsoft Store, and we would like to open source this work into the Windows Community Toolkit Labs for Windows. This small library has the following advantages:

• Makes the service registration completely trim/AOT-friendly
• Provides built-time diagnostics on registration errors

This is how you can use the library:

public sealed partial class App
{
    [Singleton(typeof(Logger), typeof(ILogger))]
    [Singleton(typeof(SomeService1), typeof(ISomeService1))]
    [Singleton(typeof(SomeService2), typeof(ISomeService2))]
    [Singleton(typeof(SomeService3), typeof(ISomeService3), typeof(IAnotherInterface))]
    [Singleton(typeof(StandaloneService))]
    [Transient(typeof(SomeViewModel))]
    // More services here...
    internal static partial void ConfigureServices(IServiceCollection services);
}

This will generate an implementation of that ConfigureServices method with registration calls for all declared services, and fully pre-generated reflection-free stubs to instantiate every service as well. That is, this will work just fine with AOT/trimming as well.

API overview

The following attributes are included:

namespace CommunityToolkit.Extensions.DependencyInjection;

[AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
[Conditional("SERVICES_CONFIGURATION_METADATA")]
public sealed class SingletonAttribute : Attribute
{
    public SingletonAttribute(Type implementationType, params Type[] serviceTypes);

    public Type ImplementationType { get; }
    public Type[] ServiceTypes { get; }
}

[AttributeUsage(AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
[Conditional("SERVICES_CONFIGURATION_METADATA")]
public sealed class TransientAttribute : Attribute
{
    public TransientAttribute(Type implementationType, params Type[] serviceTypes);

    public Type ImplementationType { get; }
    public Type[] ServiceTypes { get; }
}

We could of course also add [Scoped] if necessary.

[dongle-the-gadget]

What if we need to supply our own values?

[Sergio0694]

What do you mean "our own values", can you make an example?

[dongle-the-gadget]

I mean, providing our own implementation, for instance
col.AddSingleton<InterfaceA, ImplementationA>(_ => new ImplementationA("something"));

[AbdAlghaniAlbiek]

Then if you need inject these services inside ViewModels will be the same classic way (App.services.GetRequiredService<>()) OR it will be automatically using some "Attributes" like this:

[SomeAttribute]
public partial class ViewModel 
{
    [CustomAttribute]
    private ISomeService1;

    [CustomAttribute]
    private ISomeService2;
}

[Mrxx99]

Wouldn't this make more sense in the MVVM toolkit instead of the windows toolkit, so it can be used not only with WinUI?

[michael-hawker]

I think that'd be where it would end up ultimately, we just don't have a similar '.NET Community Toolkit Labs' setup, so @Sergio0694 just wanted to use our infrastructure here for prototyping, feedback, and fine-tuning before figuring out where it goes. Right Sergio?

[Sergio0694]

I'm confused as to what the issue is. The package can already be used everywhere, it doesn't depend on WinUI at all (eg. we're using in on UWP in the Microsoft Store). It's just in the Labs for Windows repo for convenience, but the package just targets .NET Standard 2.0, so you can literally use it on whatever framework you want with no limitations 🙂

[MitchRazga]

I would be very interested in this experiment. Sergio and the team have an excellent track record for delivering high-quality and performant source generators. However, I am curious to know how this would distinguish itself or offer any advantages compared to other popular solutions, such as Jab and StrongInject

[Arlodotexe]

This experiment is now available in Labs, here.

[dongle-the-gadget]

@Sergio0694 I installed version 0.1.230830 and it seems that the generator would create code that passes in the IServiceCollection into ServiceProviderServiceExtensions.GetRequiredService as an argument, which doesn't work (as the method only accepts an IServiceProvider)

Note that this bug doesn't reproduce if the IServiceCollection argument is named services.

Minimal sample to trigger this bug

using CommunityToolkit.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;

namespace TKDIBugRepo;

static partial class Program
{
    static void Main()
    {

    }

    [Singleton(typeof(Foo))]
    [Singleton(typeof(Test))]
    static partial void ConfigureServices(IServiceCollection collection);
}

public class Foo
{ }

public class Test
{
    private readonly Foo _foo;

    public Test(Foo foo)
        => _foo = foo;
}

Generated code

// <auto-generated/>
#pragma warning disable
#nullable enable
 
namespace TKDIBugRepo
{
    /// <inheritdoc/>
    partial class Program
    {
        /// <inheritdoc/>
        [global::System.CodeDom.Compiler.GeneratedCode("CommunityToolkit.Extensions.DependencyInjection.SourceGenerators.ServiceProviderGenerator", "1.0.0.0")]
        [global::System.Diagnostics.DebuggerNonUserCode]
        [global::System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
        static partial void ConfigureServices(global::Microsoft.Extensions.DependencyInjection.IServiceCollection collection)
        {
            global::Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddSingleton(collection, typeof(global::TKDIBugRepo.Foo), new global::TKDIBugRepo.Foo());
            global::Microsoft.Extensions.DependencyInjection.ServiceCollectionServiceExtensions.AddSingleton(collection, typeof(global::TKDIBugRepo.Test), static services => new global::TKDIBugRepo.Test(
                global::Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService<global::TKDIBugRepo.Foo>(collection)));
        }
    }
}

Suggestion for fix

Replace info.Method.ServiceCollectionParameterName with services?

Labs-Windows/components/Extensions.DependencyInjection/CommunityToolkit.Extensions.DependencyInjection.SourceGenerators/ServiceProviderGenerator.Execute.cs

Line 195 in dff647f

.AddArgumentListArguments(Argument(IdentifierName(info.Method.ServiceCollectionParameterName))))

[antoniovalentini]

Hey @Sergio0694, the new package is not in the official feed yet, right? Any ETA for when (or if) this will happen?
Let us know if we can help as a community in any way. Thanks for your hard work 🙏

[shmuelie]

Requesting support for registering more than one implementation of an interface, something like

public class Something(IEnumerable<IService> service) { }

[SingletonGroup(typeof(Impl1), typeof(IService))]
[SingletonGroup(typeof(Impl2), typeof(IService))]
[Singleton(typeof(Something))]
internal static partial void ConfigureServices(IServiceCollection services);

[shmuelie]

Requesting support for Keyed Services:

public class SomethingA([FromKeyedServices("key1")]IService service) { }
public class SomethingB(IEnumerable<IService> service) { }

[Singleton("key1", typeof(Impl1), typeof(IService))]
[Singleton("key2", typeof(Impl2), typeof(IService))]
[Singleton(typeof(SomethingA))]
[Singleton(typeof(SomethingB))]
internal static partial void ConfigureServices(IServiceCollection services);

Asking for the services as enumerable without a key should use KeyedService.AnyKey