From dae55edfec80090dd2aa7ba0f66f3e5009303151 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mladen=20Macanovi=C4=87?= <mladen.macanovic@gmail.com>
Date: Fri, 6 Mar 2020 14:38:49 +0100
Subject: [PATCH] Add IComponentActivator

---
 .../Components/src/ComponentFactory.cs        |  8 +++-
 .../src/DefaultComponentActivator.cs          | 19 ++++++++++
 .../Components/src/IComponentActivator.cs     | 20 ++++++++++
 .../Components/test/ComponentFactoryTest.cs   | 37 +++++++++++++++++++
 .../ComponentServiceCollectionExtensions.cs   |  1 +
 ...MvcViewFeaturesMvcCoreBuilderExtensions.cs |  3 +-
 6 files changed, 86 insertions(+), 2 deletions(-)
 create mode 100644 src/Components/Components/src/DefaultComponentActivator.cs
 create mode 100644 src/Components/Components/src/IComponentActivator.cs

diff --git a/src/Components/Components/src/ComponentFactory.cs b/src/Components/Components/src/ComponentFactory.cs
index bf5de30d2a..3ba141834b 100644
--- a/src/Components/Components/src/ComponentFactory.cs
+++ b/src/Components/Components/src/ComponentFactory.cs
@@ -6,6 +6,7 @@ using System.Collections.Concurrent;
 using System.Linq;
 using System.Reflection;
 using Microsoft.AspNetCore.Components.Reflection;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Components
 {
@@ -25,7 +26,12 @@ namespace Microsoft.AspNetCore.Components
 
         public IComponent InstantiateComponent(IServiceProvider serviceProvider, Type componentType)
         {
-            var instance = Activator.CreateInstance(componentType);
+            var activator = serviceProvider.GetService<IComponentActivator>();
+
+            var instance = activator != null
+                ? activator.CreateInstance(componentType)
+                : Activator.CreateInstance(componentType);
+
             if (!(instance is IComponent component))
             {
                 throw new ArgumentException($"The type {componentType.FullName} does not implement {nameof(IComponent)}.", nameof(componentType));
diff --git a/src/Components/Components/src/DefaultComponentActivator.cs b/src/Components/Components/src/DefaultComponentActivator.cs
new file mode 100644
index 0000000000..4f93188f2f
--- /dev/null
+++ b/src/Components/Components/src/DefaultComponentActivator.cs
@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNetCore.Components
+{
+    /// <summary>
+    /// Default implementation of component activator.
+    /// </summary>
+    public class DefaultComponentActivator : IComponentActivator
+    {
+        /// <inheritdoc />
+        public IComponent? CreateInstance(Type componentType)
+        {
+            return Activator.CreateInstance(componentType) as IComponent;
+        }
+    }
+}
diff --git a/src/Components/Components/src/IComponentActivator.cs b/src/Components/Components/src/IComponentActivator.cs
new file mode 100644
index 0000000000..e98e111a05
--- /dev/null
+++ b/src/Components/Components/src/IComponentActivator.cs
@@ -0,0 +1,20 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNetCore.Components
+{
+    /// <summary>
+    /// Represents an activator that can be used to instantiate components.
+    /// </summary>
+    public interface IComponentActivator
+    {
+        /// <summary>
+        /// Creates an component of the specified type using that type's default constructor.
+        /// </summary>
+        /// <param name="componentType">The type of component to create.</param>
+        /// <returns>A reference to the newly created component.</returns>
+        IComponent? CreateInstance(Type componentType);
+    }
+}
diff --git a/src/Components/Components/test/ComponentFactoryTest.cs b/src/Components/Components/test/ComponentFactoryTest.cs
index 4dd4de56e0..662351bd6f 100644
--- a/src/Components/Components/test/ComponentFactoryTest.cs
+++ b/src/Components/Components/test/ComponentFactoryTest.cs
@@ -27,6 +27,32 @@ namespace Microsoft.AspNetCore.Components
             Assert.IsType<EmptyComponent>(instance);
         }
 
+        [Fact]
+        public void InstantiateComponent_CreatesInstance_WithActivator()
+        {
+            // Arrange
+            var componentType = typeof(EmptyComponent);
+            var factory = new ComponentFactory();
+
+            // Act
+            var instance = factory.InstantiateComponent(GetServiceProviderWithActivator(), componentType);
+
+            // Assert
+            Assert.NotNull(instance);
+            Assert.IsType<EmptyComponent>(instance);
+        }
+
+        [Fact]
+        public void InstantiateComponent_CreatesInstance_WithActivator_NonComponent()
+        {
+            // Arrange
+            var componentType = typeof(NonComponent);
+            var factory = new ComponentFactory();
+
+            // Assert
+            Assert.Throws<ArgumentException>(()=>factory.InstantiateComponent(GetServiceProviderWithActivator(), componentType));
+        }
+
         [Fact]
         public void InstantiateComponent_AssignsPropertiesWithInjectAttribute()
         {
@@ -96,6 +122,15 @@ namespace Microsoft.AspNetCore.Components
                 .BuildServiceProvider();
         }
 
+        private static IServiceProvider GetServiceProviderWithActivator()
+        {
+            return new ServiceCollection()
+                .AddTransient<TestService1>()
+                .AddTransient<TestService2>()
+                .AddSingleton<IComponentActivator, DefaultComponentActivator>()
+                .BuildServiceProvider();
+        }
+
         private class EmptyComponent : IComponent
         {
             public void Attach(RenderHandle renderHandle)
@@ -162,6 +197,8 @@ namespace Microsoft.AspNetCore.Components
             public TestService2 Property5 { get; set; }
         }
 
+        private class NonComponent { }
+
         public class TestService1 { }
         public class TestService2 { }
     }
diff --git a/src/Components/Server/src/DependencyInjection/ComponentServiceCollectionExtensions.cs b/src/Components/Server/src/DependencyInjection/ComponentServiceCollectionExtensions.cs
index cd65b7fdc4..b8e66a4e5e 100644
--- a/src/Components/Server/src/DependencyInjection/ComponentServiceCollectionExtensions.cs
+++ b/src/Components/Server/src/DependencyInjection/ComponentServiceCollectionExtensions.cs
@@ -74,6 +74,7 @@ namespace Microsoft.Extensions.DependencyInjection
             services.AddScoped<IJSRuntime, RemoteJSRuntime>();
             services.AddScoped<INavigationInterception, RemoteNavigationInterception>();
             services.AddScoped<AuthenticationStateProvider, ServerAuthenticationStateProvider>();
+            services.AddScoped<IComponentActivator, DefaultComponentActivator>();
 
             services.TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<CircuitOptions>, CircuitOptionsJSInteropDetailedErrorsConfiguration>());
 
diff --git a/src/Mvc/Mvc.ViewFeatures/src/DependencyInjection/MvcViewFeaturesMvcCoreBuilderExtensions.cs b/src/Mvc/Mvc.ViewFeatures/src/DependencyInjection/MvcViewFeaturesMvcCoreBuilderExtensions.cs
index 84ffe50ce1..34b57eb374 100644
--- a/src/Mvc/Mvc.ViewFeatures/src/DependencyInjection/MvcViewFeaturesMvcCoreBuilderExtensions.cs
+++ b/src/Mvc/Mvc.ViewFeatures/src/DependencyInjection/MvcViewFeaturesMvcCoreBuilderExtensions.cs
@@ -212,12 +212,13 @@ namespace Microsoft.Extensions.DependencyInjection
             services.TryAddScoped<NavigationManager, HttpNavigationManager>();
             services.TryAddScoped<IJSRuntime, UnsupportedJavaScriptRuntime>();
             services.TryAddScoped<INavigationInterception, UnsupportedNavigationInterception>();
-
+            
             services.TryAddTransient<ControllerSaveTempDataPropertyFilter>();
 
             // This does caching so it should stay singleton
             services.TryAddSingleton<ITempDataProvider, CookieTempDataProvider>();
             services.TryAddSingleton<TempDataSerializer, DefaultTempDataSerializer>();
+            services.TryAddSingleton<IComponentActivator, DefaultComponentActivator>();
 
             //
             // Antiforgery