Interop between ReactiveUI.SourceGenerators ([IViewFor]) and Splat.DependencyInjection.SourceGenerator

[8alex62]

Hi everyone, I created this discussion because I use both ReactiveUI.SourceGenerators and Splat.DependencyInjection.SourceGenerator in one of my personal projects, and I noticed a behavior that I can't quite wrap my head around, so I'm looking for answers to understand the pros and cons.
Please be aware that I'm quite junior on the subject 😁.

Summary

When I register a View/ViewModel pair via the [IViewFor<TViewModel>] attribute from ReactiveUI.SourceGenerators and I register the ViewModel's dependencies via Splat.DependencyInjection.SourceGenerator (SplatRegistrations.Register* + SetupIOC()), the ViewModel's constructor parameters are not injected when the VM is resolved through the generated registration.
The only way I have found to make it work is to fall back to a Service Locator pattern inside the ViewModel's constructor, which defeats most of the point of having constructor injection generated by Splat.DI.SourceGenerator.

Context / Environment

• OS: Windows 11
• App type: Avalonia UI 11.3.13
• ReactiveUI.Avalonia 11.4.12
• ReactiveUI.SourceGenerators 2.6.1
• Splat.DependencyInjection.SourceGenerator 2.2.2

Repro

View (registered via the IViewFor source generator), as shown in the ReactiveUI.SourceGenerators README:

[IViewFor<MyCustomViewModel>(RegistrationType = SplatRegistrationType.PerRequest, ViewModelRegistrationType = SplatRegistrationType.LazySingleton)]
public partial class MyCustomView : UserControl
{
    public MyCustomView()
    {
        InitializeComponent();
    }
}

ViewModel with a constructor dependency:

public partial class MyCustomViewModel : ViewModelBase
{
    private readonly IMyService _myService;
    public MyCustomViewModel(IMyService myService)
    {
        _myService = myService;
    }
}

Service registration via Splat.DI.SourceGenerator:

public static AppBuilder BuildAvaloniaApp()
    => AppBuilder.Configure<App>()
        .UsePlatformDetect()
        .WithInterFont()
        .LogToTrace()
        .UseReactiveUI(rxui =>
        {
            rxui.WithRegistration(resolver =>
            {
                Splat.SplatRegistrations.RegisterLazySingleton<IMyService, MyService>();
                Splat.SplatRegistrations.SetupIOC();
                resolver.RegisterViewsForViewModelsSourceGenerated();
            });
        });

Observed behaviour

When the View is resolved (and therefore the VM is instantiated through the registration generated by [IViewFor]), IMyService is not injected into MyCustomViewModel, even though IMyService is correctly registered and SplatRegistrations.SetupIOC() is called.

So I need to use a workaround:

public MyCustomViewModel(IMyService myService)
{
    _myService = myService
        ?? Locator.Current.GetService<IMyService>()
        ?? throw new ArgumentNullException(nameof(myService));
}

With this Service Locator fallback in the constructor, everything works. But:

• it bypasses the whole point of Splat.DI.SourceGenerator's generated constructor resolution.
• it forces every VM to know about Locator.Current.

So I'm wondering: is this intended behaviour? If so, what's the reasoning behind it, and what would be the recommended way to combine both generators? Or did I just miss something in the setup?

Happy to provide a minimal repro repo if it helps. Thanks!