Improve HostBuilder and WebApplicationBuilder Configuration integration

[halter73]

Today WebApplicationBuilder has some hacky logic to synchronize the WebApplicationBuilder.Configuration ConfigurationManager and the HostBuilder's app IConfiguration in case any custom configuration sources have been added via HostFactoryResolver. This logic can be found here.

The synchronization is not perfect and can lead to bugs like dotnet/aspnetcore#38185. We should look into adding an API to HostBuilder to share IConfigurationBuilder(s) with the WebApplicationBuilder.

Tagging subscribers to this area: @eerhardt, @maryamariyan
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Issue Details

---

Today WebApplicationBuilder has some hacky logic to synchronize the WebApplicationBuilder.Configuration ConfigurationManager and the HostBuilder's app IConfiguration in case any custom configuration sources have been added via HostFactoryResolver. This logic can be found here.

The synchronization is not perfect and can lead to bugs like dotnet/aspnetcore#38185. We should look into adding an API to HostBuilder to share an IConfigurationBuilder with the WebApplicationBuilder.

Author:	halter73
Assignees:	-
Labels:	api-suggestion, area-Extensions-Hosting
Milestone:	-

[eerhardt]

@halter73 - Do you have an idea of what the API would look like? Can you update the issue to use the API proposal template?

https://github.com/dotnet/runtime/issues/new?assignees=&labels=api-suggestion&template=02_api_proposal.yml&title=%5BAPI+Proposal%5D%3A+

[halter73]

Here's an API proposal that's an alternative to IHostBuilder. It would be a better base for WebApplicationBuilder then the IHostBuilder interface, but I think it all-around a more convenient API than IHostBuilder because it relies less on multi-stage config (instead leveraging ConfigurationManager) and callbacks that are run during build.

diff --git a/src/libraries/Microsoft.Extensions.Hosting/ref/Microsoft.Extensions.Hosting.cs b/src/libraries/Microsoft.Extensions.Hosting/ref/Microsoft.Extensions.Hosting.cs
index 742dde5a32a..0434b96536f 100644
--- a/src/libraries/Microsoft.Extensions.Hosting/ref/Microsoft.Extensions.Hosting.cs
+++ b/src/libraries/Microsoft.Extensions.Hosting/ref/Microsoft.Extensions.Hosting.cs
@@ -25,9 +25,31 @@ public partial class ConsoleLifetimeOptions
     }
     public static partial class Host
     {
+        public static Microsoft.Extensions.Hosting.HostApplicationBuilder CreateApplicationBuilder() { throw null; }
+        public static Microsoft.Extensions.Hosting.HostApplicationBuilder CreateApplicationBuilder(string[] args) { throw null; }
         public static Microsoft.Extensions.Hosting.IHostBuilder CreateDefaultBuilder() { throw null; }
         public static Microsoft.Extensions.Hosting.IHostBuilder CreateDefaultBuilder(string[] args) { throw null; }
     }
+    public partial class HostApplicationBuilder
+    {
+        public HostApplicationBuilder(Microsoft.Extensions.Hosting.HostApplicationOptions options) { }
+        public Microsoft.Extensions.Configuration.ConfigurationManager Configuration { get { throw null; } }
+        public Microsoft.Extensions.Hosting.IHostEnvironment Environment { get { throw null; } }
+        public Microsoft.Extensions.Logging.ILoggingBuilder Logging { get { throw null; } }
+        public Microsoft.Extensions.DependencyInjection.IServiceCollection Services { get { throw null; } }
+        public Microsoft.Extensions.Hosting.IHost Build() { throw null; }
+        public Microsoft.Extensions.Hosting.IHost Build<TContainerBuilder>(Microsoft.Extensions.DependencyInjection.IServiceProviderFactory<TContainerBuilder> serviceProviderFactory) { throw null; }
+    }
+    public partial class HostApplicationOptions
+    {
+        public HostApplicationOptions() { }
+        public string ApplicationName { get { throw null; } set { } }
+        public string[] Args { get { throw null; } set { } }
+        public string ContentRootPath { get { throw null; } set { } }
+        public bool DisableDefaults { get { throw null; } set { } }
+        public string EnvironmentName { get { throw null; } set { } }
+        public Microsoft.Extensions.Configuration.ConfigurationManager InitialConfiguration { get { throw null; } set { } }
+    }
     public partial class HostBuilder : Microsoft.Extensions.Hosting.IHostBuilder
     {
         public HostBuilder() { }

Sample Usage

var builder = Host.CreateApplicationBuilder(args);

builder.Configuration.AddJsonFile("myconfig.json");
Console.WriteLine($"MyConfigVariable = ${builder.Configuration["MyConfigVariable"]}");

builder.Services.AddHostedService<MyHostedService>();

var minConsoleLogLevel = builder.Environment.IsDevelopment() ? LogLevel.Trace : LogLevel.Warning;
builder.Logging.AddFilter<ConsoleLoggerProvider>(level => level >= minConsoleLogLevel);

builder.Build().Run();

Equivalent HostBuilder Sample

var builder = Host.CreateDefaultBuilder(args)
    .ConfigureAppConfiguration(hostConfig =>
    {
        hostConfig.AddJsonFile("myconfig.json");
    })
    .ConfigureServices((context, services) =>
    {
        Console.WriteLine($"MyConfigVariable = ${context.Configuration["MyConfigVariable"]}");
        services.AddHostedService<MyHostedService>();
    })
    .ConfigureLogging((context, logging) =>
    {
        var minConsoleLogLevel = context.HostingEnvironment.IsDevelopment() ? LogLevel.Trace : LogLevel.Warning;
        logging.AddFilter<ConsoleLoggerProvider>(level => level >= minConsoleLogLevel);
    });

builder.Build().Run();

I've started experimenting with this API here. And you can see how it might be consumed from WebApplicationBuilder here. It seems like we can share a fair amount of logic with the existing HostBuilder and share the same Host. I'm going to close #61635 because it's resolved by the same API.

The name of the new types are HostApplicationBuilder and HostApplicationOptions to somewhat align with similar concepts in ASP.NET (WebApplicationBuilder and WebApplicationOptions). I welcome better name recommendations.

[ladeak]

I have been looking at the implementation of WebApplicationBuilder from Asp.Net Core, to see how the sync can be done.

I would like to apply the same logic for Console Apps using GenericHost. What I see is that I would need to copy multiple times the sources back and forth between the Generic Host's configuration builder and ConfigurationManager.