Add overload of UseTypeActivator(...) that accepts an instance of IServiceProvider

CliFx.Tests/CliFx.Tests.csproj

@@ -14,6 +14,7 @@
     <PackageReference Include="FluentAssertions" Version="6.7.0" />
     <PackageReference Include="GitHubActionsTestLogger" Version="2.0.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.2.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.2.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" PrivateAssets="all" />

CliFx.Tests/TypeActivationSpecs.cs

@@ -4,6 +4,7 @@ using System.Threading.Tasks;
 using CliFx.Infrastructure;
 using CliFx.Tests.Utils;
 using FluentAssertions;
+using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -87,7 +88,7 @@ public class Command : ICommand
     }
 
     [Fact]
-    public async Task Delegate_type_activator_can_initialize_a_type_using_a_custom_function()
+    public async Task Custom_type_activator_can_initialize_a_type_using_a_given_function()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(
@@ -110,7 +111,7 @@ public class Command : ICommand
         var application = new CliApplicationBuilder()
             .AddCommand(commandType)
             .UseConsole(FakeConsole)
-            .UseTypeActivator(type => Activator.CreateInstance(type, "hello world")!)
+            .UseTypeActivator(type => Activator.CreateInstance(type, "Hello world")!)
             .Build();
 
         // Act
@@ -123,11 +124,55 @@ public class Command : ICommand
 
         // Assert
         exitCode.Should().Be(0);
-        stdOut.Trim().Should().Be("hello world");
+        stdOut.Trim().Should().Be("Hello world");
     }
 
     [Fact]
-    public async Task Delegate_type_activator_fails_if_the_underlying_function_returns_null()
+    public async Task Custom_type_activator_can_initialize_a_type_using_a_service_provider()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
+[Command]
+public class Command : ICommand
+{
+    private readonly string _foo;
+
+    public Command(string foo) => _foo = foo;
+
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        console.Output.WriteLine(_foo);
+        return default;
+    }
+}");
+
+        var serviceProvider = new ServiceCollection()
+            .AddSingleton(commandType, Activator.CreateInstance(commandType, "Hello world")!)
+            .BuildServiceProvider();
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .UseTypeActivator(serviceProvider)
+            .Build();
+
+        // Act
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
+
+        var stdOut = FakeConsole.ReadOutputString();
+
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().Be("Hello world");
+    }
+
+    [Fact]
+    public async Task Custom_type_activator_fails_if_the_underlying_function_returns_null()
     {
         // Arrange
         var commandType = DynamicCommandBuilder.Compile(

CliFx/CliApplicationBuilder.cs

@@ -182,6 +182,12 @@ public partial class CliApplicationBuilder
     public CliApplicationBuilder UseTypeActivator(Func<Type, object> typeActivator) =>
         UseTypeActivator(new DelegateTypeActivator(typeActivator));
 
+    /// <summary>
+    /// Configures the application to use the specified service provider for activating types.
+    /// </summary>
+    public CliApplicationBuilder UseTypeActivator(IServiceProvider serviceProvider) =>
+        UseTypeActivator(serviceProvider.GetService);
+
     /// <summary>
     /// Creates a configured instance of <see cref="CliApplication"/>.
     /// </summary>