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

[ghost]

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.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[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