Make it easier to add hosting services

Fixes https://github.com/aspnet/Hosting/issues/145

src/Microsoft.AspNet.Hosting/ConfigureHostingEnvironment.cs

@@ -17,7 +17,7 @@ namespace Microsoft.AspNet.Hosting
 
         public void Configure(IHostingEnvironment hostingEnv)
         {
-            hostingEnv.EnvironmentName = _config.Get(EnvironmentKey) ?? hostingEnv.EnvironmentName;
+            hostingEnv.EnvironmentName = _config?.Get(EnvironmentKey) ?? hostingEnv.EnvironmentName;
         }
     }
 }

src/Microsoft.AspNet.Hosting/HostingServices.cs

@@ -14,44 +14,66 @@ namespace Microsoft.AspNet.Hosting
 {
     public static class HostingServices
     {
-        private static IServiceCollection Import(IServiceProvider fallbackProvider)
+        private static IServiceCollection Import(IServiceProvider fallbackProvider, Action<IServiceCollection> configureHostServices)
         {
             var services = new ServiceCollection();
+            if (configureHostServices != null)
+            {
+                configureHostServices(services);
+            }
             var manifest = fallbackProvider.GetRequiredService<IServiceManifest>();
             foreach (var service in manifest.Services)
             {
                 services.AddTransient(service, sp => fallbackProvider.GetService(service));
             }
+            services.AddSingleton<IServiceManifest>(sp => new HostingManifest(services));
             return services;
         }
 
-        public static IServiceCollection Create(IConfiguration configuration = null)
+        public static IServiceCollection Create()
         {
-            return Create(CallContextServiceLocator.Locator.ServiceProvider, configuration);
+            return Create(CallContextServiceLocator.Locator.ServiceProvider, configureHostServices: null, configuration: null);
         }
 
-        public static IServiceCollection Create(IServiceProvider fallbackServices, IConfiguration configuration = null)
+        public static IServiceCollection Create(IServiceProvider fallbackServices)
         {
-            configuration = configuration ?? new Configuration();
-            var services = Import(fallbackServices);
+            return Create(fallbackServices, configureHostServices: null, configuration: null);
+        }
+
+        public static IServiceCollection Create(IServiceProvider fallbackServices, Action<IServiceCollection> configureHostServices)
+        {
+            return Create(fallbackServices, configureHostServices, configuration: null);
+        }
+
+        public static IServiceCollection Create(Action<IServiceCollection> configureHostServices, IConfiguration configuration)
+        {
+            return Create(CallContextServiceLocator.Locator.ServiceProvider, configureHostServices, configuration);
+        }
+
+        public static IServiceCollection Create(IServiceProvider fallbackServices, IConfiguration configuration)
+        {
+            return Create(CallContextServiceLocator.Locator.ServiceProvider, configureHostServices: null, configuration: configuration);
+        }
+
+        public static IServiceCollection Create(IServiceProvider fallbackServices, Action<IServiceCollection> configureHostServices, IConfiguration configuration)
+        {
+            var services = Import(fallbackServices, configureHostServices);
             services.AddHosting(configuration);
-            services.AddSingleton<IServiceManifest>(sp => new HostingManifest(fallbackServices));
             return services;
         }
 
         // Manifest exposes the fallback manifest in addition to ITypeActivator, IHostingEnvironment, and ILoggerFactory
         private class HostingManifest : IServiceManifest
         {
-            public HostingManifest(IServiceProvider fallback)
+            public HostingManifest(IServiceCollection hostServices)
             {
-                var manifest = fallback.GetRequiredService<IServiceManifest>();
                 Services = new Type[] {
                     typeof(ITypeActivator),
                     typeof(IHostingEnvironment),
                     typeof(ILoggerFactory),
                     typeof(IHttpContextAccessor),
                     typeof(IApplicationLifetime)
-                }.Concat(manifest.Services).Distinct();
+                }.Concat(hostServices.Select(s => s.ServiceType)).Distinct();
             }
 
             public IEnumerable<Type> Services { get; private set; }

src/Microsoft.AspNet.Hosting/HostingServicesCollectionExtensions.cs

@@ -11,7 +11,12 @@ namespace Microsoft.Framework.DependencyInjection
 {
     public static class HostingServicesExtensions
     {
-        public static IServiceCollection AddHosting(this IServiceCollection services, IConfiguration configuration = null)
+        public static IServiceCollection AddHosting(this IServiceCollection services)
+        {
+            return services.AddHosting(configuration: null);
+        }
+
+        public static IServiceCollection AddHosting(this IServiceCollection services, IConfiguration configuration)
         {
             services.TryAdd(ServiceDescriptor.Transient<IHostingEngine, HostingEngine>());
             services.TryAdd(ServiceDescriptor.Transient<IServerLoader, ServerLoader>());

src/Microsoft.AspNet.TestHost/TestServer.cs

@@ -47,12 +47,22 @@ namespace Microsoft.AspNet.TestHost
 
         public static TestServer Create(Action<IApplicationBuilder> app)
         {
-            return Create(CallContextServiceLocator.Locator.ServiceProvider, app);
+            return Create(CallContextServiceLocator.Locator.ServiceProvider, app, configureHostServices: null);
+        }
+
+        public static TestServer Create(Action<IApplicationBuilder> app, Action<IServiceCollection> configureHostServices)
+        {
+            return Create(CallContextServiceLocator.Locator.ServiceProvider, app, configureHostServices);
         }
 
         public static TestServer Create(IServiceProvider serviceProvider, Action<IApplicationBuilder> app)
         {
-            var appServices = HostingServices.Create(serviceProvider).BuildServiceProvider();
+            return Create(serviceProvider, app, configureHostServices: null);
+        }
+
+        public static TestServer Create(IServiceProvider serviceProvider, Action<IApplicationBuilder> app, Action<IServiceCollection> configureHostServices)
+        {
+            var appServices = HostingServices.Create(serviceProvider, configureHostServices).BuildServiceProvider();
             var config = new Configuration();
             return new TestServer(config, appServices, app);
         }

test/Microsoft.AspNet.Hosting.Tests/HostingServicesFacts.cs

@@ -52,6 +52,73 @@ namespace Microsoft.AspNet.Hosting.Tests
             Assert.Null(provider.GetService<IFakeScopedService>()); // Make sure we don't leak non manifest services
         }
 
+        [Fact]
+        public void CreateCanAddAdditionalServices()
+        {
+            // Arrange
+            var fallbackServices = new ServiceCollection();
+            fallbackServices.AddTransient<IFakeService, FakeService>();
+            fallbackServices.AddTransient<IFakeScopedService, FakeService>(); // Don't register in manifest
+
+            fallbackServices.AddInstance<IServiceManifest>(new ServiceManifest(
+                new Type[] {
+                    typeof(IFakeService),
+                }));
+
+            var instance = new FakeService();
+            var factoryInstance = new FakeFactoryService(instance);
+
+            var services = HostingServices.Create(fallbackServices.BuildServiceProvider(),
+                additionalHostServices =>
+                {
+                    additionalHostServices.AddSingleton<IFakeSingletonService, FakeService>();
+                    additionalHostServices.AddInstance<IFakeServiceInstance>(instance);
+                    additionalHostServices.AddSingleton<IFactoryService>(serviceProvider => factoryInstance);
+                });
+
+            // Act
+            var provider = services.BuildServiceProvider();
+            var singleton = provider.GetRequiredService<IFakeSingletonService>();
+            var transient = provider.GetRequiredService<IFakeService>();
+            var factory = provider.GetRequiredService<IFactoryService>();
+            var manifest = provider.GetRequiredService<IServiceManifest>();
+
+            // Assert
+            Assert.Same(singleton, provider.GetRequiredService<IFakeSingletonService>());
+            Assert.NotSame(transient, provider.GetRequiredService<IFakeService>());
+            Assert.Same(instance, provider.GetRequiredService<IFakeServiceInstance>());
+            Assert.Same(factoryInstance, factory);
+            Assert.Same(factory.FakeService, instance);
+            Assert.Null(provider.GetService<INonexistentService>());
+            Assert.Null(provider.GetService<IFakeScopedService>()); // Make sure we don't leak non manifest services
+            Assert.Contains(typeof(IFakeSingletonService), manifest.Services);
+            Assert.Contains(typeof(IFakeServiceInstance), manifest.Services);
+            Assert.Contains(typeof(IFactoryService), manifest.Services);
+        }
+
+        [Fact]
+        public void CreateAdditionalServicesDoNotOverrideFallback()
+        {
+            // Arrange
+            var fallbackServices = new ServiceCollection();
+            fallbackServices.AddTransient<IFakeService, FakeService>();
+
+            fallbackServices.AddInstance<IServiceManifest>(new ServiceManifest(
+                new Type[] {
+                    typeof(IFakeService),
+                }));
+
+            var services = HostingServices.Create(fallbackServices.BuildServiceProvider(), 
+                additionalHostServices => additionalHostServices.AddSingleton<IFakeService, FakeService>());
+
+            // Act
+            var provider = services.BuildServiceProvider();
+            var stillTransient = provider.GetRequiredService<IFakeService>();
+
+            // Assert
+            Assert.NotSame(stillTransient, provider.GetRequiredService<IFakeService>());
+        }
+
         [Fact]
         public void CanHideImportedServices()
         {

test/Microsoft.AspNet.Hosting.Tests/Microsoft.AspNet.Hosting.Tests.kproj

@@ -12,7 +12,7 @@
   </PropertyGroup>
   <PropertyGroup>
     <SchemaVersion>2.0</SchemaVersion>
-    <DevelopmentServerPort>23533</DevelopmentServerPort>
+    <DevelopmentServerPort>18007</DevelopmentServerPort>
   </PropertyGroup>
   <Import Project="$(VSToolsPath)\AspNet\Microsoft.Web.AspNet.targets" Condition="'$(VSToolsPath)' != ''" />
 </Project>

test/Microsoft.AspNet.TestHost.Tests/TestServerTests.cs

@@ -10,6 +10,7 @@ using Microsoft.AspNet.Builder;
 using Microsoft.AspNet.Hosting;
 using Microsoft.AspNet.Http;
 using Microsoft.Framework.DependencyInjection;
+using Microsoft.Framework.Logging;
 using Xunit;
 
 namespace Microsoft.AspNet.TestHost
@@ -36,10 +37,25 @@ namespace Microsoft.AspNet.TestHost
             Assert.Throws<InvalidOperationException>(() => TestServer.Create(services, new Startup().Configuration));
         }
 
+        [Fact]
+        public async Task CanAccessLogger()
+        {
+            TestServer server = TestServer.Create(app =>
+            {
+                app.Run(context =>
+                {
+                    var logger = app.ApplicationServices.GetRequiredService<ILogger<HttpContext>>();
+                    return context.Response.WriteAsync("FoundLogger:" + (logger != null));
+                });
+            });
+
+            string result = await server.CreateClient().GetStringAsync("/path");
+            Assert.Equal("FoundLogger:True", result);
+        }
+
         [Fact]
         public async Task CanAccessHttpContext()
         {
-            var services = new ServiceCollection().BuildServiceProvider();
             TestServer server = TestServer.Create(app =>
             {
                 app.Run(context =>
@@ -53,6 +69,35 @@ namespace Microsoft.AspNet.TestHost
             Assert.Equal("HasContext:True", result);
         }
 
+        public class ContextHolder
+        {
+            public ContextHolder(IHttpContextAccessor accessor)
+            {
+                Accessor = accessor;
+            }
+
+            public IHttpContextAccessor Accessor { get; set; }
+        }
+
+        [Fact]
+        public async Task CanAddNewHostServices()
+        {
+            TestServer server = TestServer.Create(app =>
+            {
+                var a = app.ApplicationServices.GetRequiredService<IHttpContextAccessor>();
+
+                app.Run(context =>
+                {
+                    var b = app.ApplicationServices.GetRequiredService<IHttpContextAccessor>();
+                    var accessor = app.ApplicationServices.GetRequiredService<ContextHolder>();
+                    return context.Response.WriteAsync("HasContext:" + (accessor.Accessor.HttpContext != null));
+                });
+            }, newHostServices => newHostServices.AddSingleton<ContextHolder>());
+
+            string result = await server.CreateClient().GetStringAsync("/path");
+            Assert.Equal("HasContext:True", result);
+        }
+
         [Fact]
         public async Task CreateInvokesApp()
         {