ResolveServiceProviderFactory should work with Minimal Hosting

[shirhatti]

Tools like EF migration rely on Program.CreateDefaultBuilder() at build-time to build the service container and resolve services (like DbContext).

https://github.com/dotnet/runtime/blob/main/src/libraries/Microsoft.Extensions.HostFactoryResolver/src/HostFactoryResolver.cs

[javiercn]

@shirhatti also Microsoft.AspNetCore.Mvc.Testing depends on that

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. Because it's not immediately obvious that this is a bug in our framework, we would like to keep this around to collect more feedback, which can later help us determine the impact of it. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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[DamianEdwards]

I'm wondering if we could use a startup hook to enable this somehow, rather than boilerplate code that must be in the app for it to work. Alternatively, could we use a source generator that's enabled by the invoking tool (e.g. dotnet ef) to generate the required pattern or hook somehow.

[davidfowl]

I had an idea that we could use a diagnostic source for this but that won't work since this pattern basically wants a public API that is callable.

EF - https://github.com/dotnet/efcore/blob/ac2bb48b10ecf1289b568a94b7a35e8075c6d787/src/EFCore.Design/Design/Internal/AppServiceProviderFactory.cs#L49-L59
Testing -

aspnetcore/src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

Lines 339 to 347 in fdd687b

	protected virtual IHostBuilder CreateHostBuilder()
	{
	var hostBuilder = HostFactoryResolver.ResolveHostBuilderFactory<IHostBuilder>(typeof(TEntryPoint).Assembly)?.Invoke(Array.Empty<string>());
	if (hostBuilder != null)
	{
	hostBuilder.UseEnvironment(Environments.Development);
	}
	return hostBuilder;
	}

These rely on a callable entrypoint.

[davidfowl]

Actually we might still be able to do this.

[davidfowl]

This is fixed by

• Fire diagnostic source events from IHostBuilder.Build runtime#53757
• Follow up on HostFactoryResolver changes runtime#54052
• Scope events to the execution of the entry point runtime#54090

WebApplicationFactory support

• Support the new top level statements with WebApplicationFactory #33462