feature: expand Microsoft.Extensions.Hosting support to allow work to be done prior to Run*Async() (#409)

Author: hellfirehd

README.md

@@ -129,3 +129,5 @@ The library also includes other utilities for interaction with the console. Thes
     ```
 
 And more! See the [documentation](https://natemcmaster.github.io/CommandLineUtils/) for more API, such as `IConsole`, `IReporter`, and others.
+
+

src/Hosting.CommandLine/HostBuilderExtensions.cs

@@ -145,5 +145,49 @@ public static async Task<int> RunCommandLineApplicationAsync(
 
             return state.ExitCode;
         }
+
+        /// <summary>
+        ///     Configures an instance of <typeparamref name="TApp" /> using <see cref="CommandLineApplication" /> to provide
+        ///     command line parsing on the given <paramref name="args" />.
+        /// </summary>
+        /// <typeparam name="TApp">The type of the command line application implementation</typeparam>
+        /// <param name="hostBuilder">This instance</param>
+        /// <param name="args">The command line arguments</param>
+        /// <param name="configure">The delegate to configure the application</param>
+        /// <returns><see cref="IHostBuilder"/></returns>
+        public static IHostBuilder UseCommandLineApplication<TApp>(
+            this IHostBuilder hostBuilder,
+            string[] args,
+            Action<CommandLineApplication<TApp>> configure = null)
+            where TApp : class
+        {
+            configure ??= app => { };
+            var state = new CommandLineState(args);
+            hostBuilder.Properties[typeof(CommandLineState)] = state;
+            hostBuilder.ConfigureServices(
+                (context, services)
+                    =>
+                {
+                    services
+                        .TryAddSingleton<StoreExceptionHandler>();
+                    services
+                        .TryAddSingleton<IUnhandledExceptionHandler>(provider => provider.GetRequiredService<StoreExceptionHandler>());
+                    services
+                        .AddSingleton<IHostLifetime, CommandLineLifetime>()
+                        .TryAddSingleton(PhysicalConsole.Singleton);
+                    services
+                        .AddSingleton(provider =>
+                        {
+                            state.SetConsole(provider.GetService<IConsole>());
+                            return state;
+                        })
+                        .AddSingleton<CommandLineContext>(state)
+                        .AddSingleton<ICommandLineService, CommandLineService<TApp>>();
+                    services
+                        .AddSingleton(configure);
+                });
+
+            return hostBuilder;
+        }
     }
 }

src/Hosting.CommandLine/HostExtensions.cs

@@ -0,0 +1,44 @@
+// Copyright (c) Nate McMaster.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace Microsoft.Extensions.Hosting
+{
+    using System;
+    using System.Runtime.ExceptionServices;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using McMaster.Extensions.CommandLineUtils;
+    using McMaster.Extensions.Hosting.CommandLine.Internal;
+    using Microsoft.Extensions.DependencyInjection;
+
+    /// <summary>
+    /// Extension methods for <see cref="IHost" /> support.
+    /// </summary>
+    public static class HostExtensions
+    {
+        /// <summary>
+        /// Runs an instance of <typeparamref name="TApp" /> using the <see cref="CommandLineApplication" /> previously configured in
+        /// <see cref="HostBuilderExtensions.UseCommandLineApplication{TApp}(IHostBuilder, string[], Action{CommandLineApplication{TApp}})"/>.
+        /// </summary>
+        /// <typeparam name="TApp">The type of the command line application implementation</typeparam>
+        /// <param name="host">This instance</param>
+        /// <param name="cancellationToken">A cancellation token</param>
+        public static async Task<int> RunCommandLineApplicationAsync<TApp>(
+            this IHost host,
+            CancellationToken cancellationToken = default)
+            where TApp : class
+        {
+            var exceptionHandler = host.Services.GetService<StoreExceptionHandler>();
+            var state = host.Services.GetRequiredService<CommandLineState>();
+
+            await host.RunAsync(cancellationToken);
+
+            if (exceptionHandler?.StoredException != null)
+            {
+                ExceptionDispatchInfo.Capture(exceptionHandler.StoredException).Throw();
+            }
+
+            return state.ExitCode;
+        }
+    }
+}

src/Hosting.CommandLine/PublicAPI.Unshipped.txt

@@ -1 +1,4 @@
 #nullable enable
+static Microsoft.Extensions.Hosting.HostBuilderExtensions.UseCommandLineApplication<TApp>(this Microsoft.Extensions.Hosting.IHostBuilder! hostBuilder, string![]! args, System.Action<McMaster.Extensions.CommandLineUtils.CommandLineApplication<TApp!>!>! configure = null) -> Microsoft.Extensions.Hosting.IHostBuilder!
+Microsoft.Extensions.Hosting.HostExtensions
+static Microsoft.Extensions.Hosting.HostExtensions.RunCommandLineApplicationAsync<TApp>(this Microsoft.Extensions.Hosting.IHost! host, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<int>!