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namespace Microsoft.AspNetCore.Http.Abstractions

Nit: This should just be Microsoft.AspNetCore.Http.

without listening on an HTTP server.

Would this just prevent the IServer/GenericWebHostService from starting, or would it essentially prevent the entire host and any hosted services from starting?

Also, could this also be used to implement things like EF Core tooling?

I'm not saying we'd actually do that since dotnet ef already exists, but I wonder if we should pick a more generic name and assembly if "publishers" can do more than publish OpenAPI documents. An IApiPublisher interface in Microsoft.AspNetCore.Http seems too OpenAPI specific considering what this is capable of.

Given the shape of the API, I wonder if we could add an IPublisher interface to the Microsoft.Extensions.Hosting.Abstractions assembly and support it in all of our "generic" hosts including the ones returned by HostApplicationBuilder and new HostBuilder() putting it on equal footing with IHostedService.

Would this just prevent the IServer/GenericWebHostService from starting, or would it essentially prevent the entire host and any hosted services from starting?

The former. This just prevents the IServer/GenericWebHostService from starting. The actual mechanism that discovers and executes the IApiPublisher implementations is a hosted service itself.

Also, could this also be used to implement things like EF Core tooling?

I'm not totally familiar with how the EF Core tooling works but this can be used to replace anything that relies on HostFactoryResolver + no-op IServer implementation for its core behavior at the moment.

An IApiPublisher interface in Microsoft.AspNetCore.Http seems too OpenAPI specific considering what this is capable of.

FWIW, I put the type in the abstractions assembly in the shared framework instead of the Microsoft.AspNetCore.OpenApi package since it's generally applicable.

Given the shape of the API, I wonder if we could add an IPublisher interface to the Microsoft.Extensions.Hosting.Abstractions assembly and support it in all of our "generic" hosts including the ones returned by HostApplicationBuilder and new HostBuilder() putting it on equal footing with IHostedService.

I haven't gone this far down with abstracting this API. I can see this make sense for certain builders where there is a "live" mode for the application (like running an HTTP server and listening on ports) and a "static" mode but I haven't reasoned through how that shape would look for all host types.

API Review Notes:

• More discussion about whether the publisher could move to the generic Host.cs
  • Still unresolved, but also considered moving it into the OpenApi package using hosted services.
• Why does ApiPublisherContext.Services exist? Can't you constructor inject it?
• Do we need ApiPublisherContext?
• What about taking the HttpRequest as an extension method to IOpenApiDocumentProvider

  namespace Microsoft.AspNetCore.OpenApi;
  
  public interface IOpenApiDocumentProvider
  {
    Task<OpenApiDocument> GetOpenApiDocumentAsync(string serverUri = null, CancellationToken cancellationToken = default)
  }
  
  public static class OpenApiDocumentProviderExtensions
  {
    Task<OpenApiDocument> GetOpenApiDocumentAsync(this IOpenApiDocumentProvider documentProvider, HttpRequest httpRequest, CancellationToken cancellationToken = default)
  }

• It turns out, we don't need to take the serverUri at all

API Approved! (No publisher!)

// Assembly: Microsoft.AspNetCore.OpenApi

namespace Microsoft.AspNetCore.OpenApi;

public interface IOpenApiDocumentProvider
{
    Task<OpenApiDocument> GetOpenApiDocumentAsync(CancellationToken cancellationToken = default)
}

Closing as this was addressed in #61463