Minimal hosting

[halter73]

Description

We're looking to collect feedback on our new "minimal hosting" API which we will present at BUILD. This adds quite a few types like WebApplication and WebApplicationBuilder as minimal alternative to Host and WebHost.

We are also planning to update the dotnet new empty/dotnet new web template for preview4 to use the new WebApplication type.

For this preview only, this does add temporarily a new Configuration : IConfigurationRoot, IConfigurationBuilder type to the Microsoft.AspNetCore.Builder namespace. I plan to submit a proper API proposal for to introduce this type to the Microsoft.Extensions.Configuration shortly.

Customer Impact

This is entirely new API, so the only impact is giving customers an early preview version of this new minimal hosting API to try out. It does not change any of the existing Hosts so there's no impact to existing apps.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

This change merely adds new API to an existing Microsoft.AspNetCore assembly.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

namespace Microsoft.AspNetCore.Builder
{
    public sealed class WebApplicationBuilder
    {
        public IWebHostEnvironment Environment { get; }
        public IServiceCollection Services { get; }
        public Configuration Configuration { get; }
        public ILoggingBuilder Logging { get; }

        // Ability to configure existing web host and host
        public ConfigureWebHostBuilder WebHost { get; }
        public ConfigureHostBuilder Host { get; }

        public WebApplication Build();
    }

    public sealed class Configuration : IConfigurationRoot, IConfigurationBuilder { }

    // The .Build() methods are explicitly implemented interface method that throw NotSupportedExceptions
    public sealed class ConfigureHostBuilder : IHostBuilder { }
    public sealed class ConfigureWebHostBuilder : IWebHostBuilder { }

    public sealed class WebApplication : IHost, IApplicationBuilder, IEndpointRouteBuilder, IAsyncDisposable
    {
        // Top level properties to access common services
        public ILogger Logger { get; }
        public ICollection<string> Urls { get; }
        public IHostApplicationLifetime Lifetime { get; }
        public IServiceProvider Services { get; }
        public IConfiguration Configuration { get; }
        public IWebHostEnvironment Environment { get; }

        // Factory methods
        public static WebApplication Create(string[]? args = null);
        public static WebApplicationBuilder CreateBuilder(string[]? args = null);

        // Methods used to start the host
        public void Run(string? url = nul);
        public Task RunAsync(string? url = null);
        public Task StartAsync(CancellationToken cancellationToken = default);
        public Task StopAsync(CancellationToken cancellationToken = default);

        public ValueTask DisposeAsync();
    }
}

Addresses #30354

See https://github.com/featherhttp/framework to see the original versions of all of the newly added types.

The new Configuration type should be in Microsoft.Extensions as noted in the issue. I plan to open an API proposal to do this tomorrow. I think we'll leave it in the ASP.NET Core shared runtime temporarily for preview4.

[halter73]

@Pilchie This is up for API review Monday, but we really want this in preview4. Should we try to merge this today (pending approvals ofc), or wait for API review?

[Pilchie]

We can retarget it to the Preview 4 branch and still merge on Monday after API review.

[ghost]

Hello human! Please make sure you've included the Shiproom Template in a comment or (preferably) the PR description. Also, make sure this PR is not marked as a draft and is ready-to-merge.

[BrennanConroy]

FYI, working to unblock the code check with #31982

[LadyNaggaga]

LGTM - Let's move forward so we can get in the hands of the customers for feedback.

[halter73]

/azp run

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