refactor(host): migrate BootstrapHttpClient from options to dependency injection

Directory.Packages.props

@@ -15,6 +15,7 @@
     <PackageVersion Include="AutoFixture.AutoNSubstitute" Version="4.18.1" />
     <PackageVersion Include="AutoFixture.Xunit3" Version="4.19.0" />
     <PackageVersion Include="BenchmarkDotNet" Version="0.15.6" />
+    <PackageVersion Include="Microsoft.Extensions.Http" Version="10.0.0" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
     <!-- Source Gen Libraries -->
     <PackageVersion Include="Microsoft.CSharp" Version="4.7.0" />

src/AwsLambda.Host/AwsLambda.Host.csproj

@@ -18,6 +18,7 @@
     <PackageReference Include="Amazon.Lambda.Serialization.SystemTextJson" />
     <PackageReference Include="Microsoft.Extensions.Hosting" />
     <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" />
+    <PackageReference Include="Microsoft.Extensions.Http" />
   </ItemGroup>
   <ItemGroup>
     <None Include="build\AwsLambda.Host.targets" Pack="true" PackagePath="build" Visible="true" />

src/AwsLambda.Host/Builder/Extensions/LambdaHttpClientServiceCollectionExtensions.cs

@@ -0,0 +1,107 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+namespace AwsLambda.Host.Builder.Extensions;
+
+/// <summary>
+/// Extension methods for configuring the Lambda bootstrap HTTP client in an
+/// <see cref="IServiceCollection" />.
+/// </summary>
+public static class LambdaHttpClientServiceCollectionExtensions
+{
+    extension(IServiceCollection services)
+    {
+        /// <summary>Adds a custom HTTP client instance for the Lambda bootstrap runtime API.</summary>
+        /// <typeparam name="T">The type of <see cref="HttpClient" /> to register.</typeparam>
+        /// <param name="client">The pre-configured <see cref="HttpClient" /> instance.</param>
+        /// <returns>The <see cref="IServiceCollection" /> for chaining.</returns>
+        /// <remarks>
+        ///     Registers a keyed singleton <see cref="HttpClient" /> that will be used by the Lambda
+        ///     bootstrap to communicate with the Lambda runtime API. This overload is useful for testing
+        ///     scenarios where you want to inject a mock or fake HTTP client.
+        /// </remarks>
+        public IServiceCollection AddLambdaBootstrapHttpClient<T>(T client)
+            where T : HttpClient
+        {
+            ArgumentNullException.ThrowIfNull(services);
+
+            services.AddKeyedSingleton<HttpClient>(typeof(ILambdaBootstrapOrchestrator), client);
+
+            return services;
+        }
+
+        /// <summary>
+        /// Adds a factory for creating a custom HTTP client for the Lambda bootstrap runtime API.
+        /// </summary>
+        /// <param name="factory">
+        /// A factory function that creates the <see cref="HttpClient" /> instance. The function
+        /// receives the <see cref="IServiceProvider" /> and service key.
+        /// </param>
+        /// <returns>The <see cref="IServiceCollection" /> for chaining.</returns>
+        /// <remarks>
+        ///     <para>
+        ///         Registers a keyed singleton <see cref="HttpClient" /> factory that will be used by the
+        ///         Lambda bootstrap to communicate with the Lambda runtime API. This overload provides
+        ///         access to the dependency injection container, allowing you to resolve other services
+        ///         when constructing the HTTP client.
+        ///     </para>
+        /// </remarks>
+        public IServiceCollection AddLambdaBootstrapHttpClient(
+            Func<IServiceProvider, object?, HttpClient> factory
+        )
+        {
+            ArgumentNullException.ThrowIfNull(services);
+
+            services.AddKeyedSingleton<HttpClient>(typeof(ILambdaBootstrapOrchestrator), factory);
+
+            return services;
+        }
+
+        /// <summary>
+        /// Attempts to add a custom HTTP client instance for the Lambda bootstrap runtime API if one is
+        /// not already registered.
+        /// </summary>
+        /// <typeparam name="T">The type of <see cref="HttpClient" /> to register.</typeparam>
+        /// <param name="client">The pre-configured <see cref="HttpClient" /> instance.</param>
+        /// <remarks>
+        ///     Registers a keyed singleton <see cref="HttpClient" /> that will be used by the Lambda
+        ///     bootstrap to communicate with the Lambda runtime API, but only if a keyed HTTP client has
+        ///     not already been registered. This overload is useful for testing scenarios where you want
+        ///     to inject a mock or fake HTTP client without overwriting user-supplied configurations.
+        /// </remarks>
+        public void TryAddLambdaBootstrapHttpClient<T>(T client)
+            where T : HttpClient
+        {
+            ArgumentNullException.ThrowIfNull(services);
+
+            services.TryAddKeyedSingleton<HttpClient>(typeof(ILambdaBootstrapOrchestrator), client);
+        }
+
+        /// <summary>
+        /// Attempts to add a factory for creating a custom HTTP client for the Lambda bootstrap runtime
+        /// API if one is not already registered.
+        /// </summary>
+        /// <param name="factory">
+        /// A factory function that creates the <see cref="HttpClient" /> instance. The function
+        /// receives the <see cref="IServiceProvider" /> and service key.
+        /// </param>
+        /// <remarks>
+        ///     <para>
+        ///         Registers a keyed singleton <see cref="HttpClient" /> factory that will be used by the
+        ///         Lambda bootstrap to communicate with the Lambda runtime API, but only if a keyed HTTP
+        ///         client has not already been registered.
+        ///     </para>
+        /// </remarks>
+        public void TryAddLambdaBootstrapHttpClient(
+            Func<IServiceProvider, object?, HttpClient> factory
+        )
+        {
+            ArgumentNullException.ThrowIfNull(services);
+
+            services.TryAddKeyedSingleton<HttpClient>(
+                typeof(ILambdaBootstrapOrchestrator),
+                factory
+            );
+        }
+    }
+}

src/AwsLambda.Host/Core/Options/LambdaHostOptions.cs

@@ -1,4 +1,5 @@
 using Amazon.Lambda.RuntimeSupport.Bootstrap;
+using AwsLambda.Host.Builder.Extensions;
 
 namespace AwsLambda.Host.Options;
 
@@ -8,9 +9,17 @@
     /// <summary>Gets or sets an optional custom HTTP client for the Lambda bootstrap.</summary>
     /// <remarks>
     ///     When null, the bootstrap will create its own HTTP client for communicating with the Lambda
-    ///     runtime API. Provide a custom client to control connection pooling, timeout settings, or other
-    ///     HTTP-level behaviors.
+    ///     runtime API. This property will be overridden by keyed service registrations from
+    ///     <see cref="LambdaHttpClientServiceCollectionExtensions.AddLambdaBootstrapHttpClient" /> or
+    ///     <see cref="LambdaHttpClientServiceCollectionExtensions.TryAddLambdaBootstrapHttpClient" />
+    ///     extension methods.
     /// </remarks>
+    [Obsolete(
+        "This property will be removed in version 2.0.0. Use "
+            + "AddLambdaBootstrapHttpClient() or TryAddLambdaBootstrapHttpClient() extension methods "
+            + "instead.",
+        false
+    )]
     public HttpClient? BootstrapHttpClient { get; set; } = null;
 
     /// <summary>Gets or sets the options for configuring the Lambda bootstrap behavior.</summary>

src/AwsLambda.Host/Runtime/LambdaBootstrapAdapter.cs

@@ -1,5 +1,6 @@
 using Amazon.Lambda.Core;
 using Amazon.Lambda.RuntimeSupport;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 
 namespace AwsLambda.Host.Runtime;
@@ -10,12 +11,23 @@
 /// </summary>
 internal sealed class LambdaBootstrapAdapter : ILambdaBootstrapOrchestrator
 {
+    private readonly HttpClient? _httpClient;
     private readonly LambdaHostOptions _settings;
 
-    public LambdaBootstrapAdapter(IOptions<LambdaHostOptions> lambdaHostSettings)
+    public LambdaBootstrapAdapter(
+        IOptions<LambdaHostOptions> lambdaHostSettings,
+        [FromKeyedServices(typeof(ILambdaBootstrapOrchestrator))] HttpClient? httpClient = null
+    )
     {
         ArgumentNullException.ThrowIfNull(lambdaHostSettings);
 
+        // TODO: Remove this check once ILambdaBootstrapOrchestrator.BootstrapHttpClient is removed.
+        // until ILambdaBootstrapOrchestrator.BootstrapHttpClient is removed, we need to check for
+        // it if the keyed service is NOT present.
+#pragma warning disable CS0618 // Type or member is obsolete
+        _httpClient = httpClient ?? lambdaHostSettings.Value.BootstrapHttpClient;
+#pragma warning restore CS0618 // Type or member is obsolete
+
         _settings = lambdaHostSettings.Value;
     }
 
@@ -32,10 +44,10 @@
         using var wrappedHandler = HandlerWrapper.GetHandlerWrapper(handler);
 
         // Create the bootstrap based on configuration.
-        using var bootstrap = _settings.BootstrapHttpClient is null
+        using var bootstrap = _httpClient is null
             ? new LambdaBootstrap(wrappedHandler, _settings.BootstrapOptions, convertedInitializer)
             : new LambdaBootstrap(
-                _settings.BootstrapHttpClient,
+                _httpClient,
                 wrappedHandler,
                 _settings.BootstrapOptions,
                 convertedInitializer