CR: Add ctor overload accepting IComponentActivator

src/Components/Components/ref/Microsoft.AspNetCore.Components.netcoreapp.cs

@@ -477,6 +477,7 @@ namespace Microsoft.AspNetCore.Components.RenderTree
     public abstract partial class Renderer : System.IDisposable
     {
         public Renderer(System.IServiceProvider serviceProvider, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory) { }
+        public Renderer(System.IServiceProvider serviceProvider, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory, Microsoft.AspNetCore.Components.IComponentActivator componentActivator) { }
         public abstract Microsoft.AspNetCore.Components.Dispatcher Dispatcher { get; }
         protected internal Microsoft.AspNetCore.Components.ElementReferenceContext? ElementReferenceContext { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute] protected set { } }
         public event System.UnhandledExceptionEventHandler UnhandledSynchronizationException { add { } remove { } }

src/Components/Components/src/RenderTree/Renderer.cs

@@ -59,6 +59,18 @@ namespace Microsoft.AspNetCore.Components.RenderTree
         /// <param name="serviceProvider">The <see cref="IServiceProvider"/> to be used when initializing components.</param>
         /// <param name="loggerFactory">The <see cref="ILoggerFactory"/>.</param>
         public Renderer(IServiceProvider serviceProvider, ILoggerFactory loggerFactory)
+            : this(serviceProvider, loggerFactory, GetComponentActivatorOrDefault(serviceProvider))
+        {
+            // This overload is provided for back-compatibility
+        }
+
+        /// <summary>
+        /// Constructs an instance of <see cref="Renderer"/>.
+        /// </summary>
+        /// <param name="serviceProvider">The <see cref="IServiceProvider"/> to be used when initializing components.</param>
+        /// <param name="loggerFactory">The <see cref="ILoggerFactory"/>.</param>
+        /// <param name="componentActivator">The <see cref="IComponentActivator"/>.</param>
+        public Renderer(IServiceProvider serviceProvider, ILoggerFactory loggerFactory, IComponentActivator componentActivator)
         {
             if (serviceProvider is null)
             {
@@ -70,14 +82,22 @@ namespace Microsoft.AspNetCore.Components.RenderTree
                 throw new ArgumentNullException(nameof(loggerFactory));
             }
 
+            if (componentActivator is null)
+            {
+                throw new ArgumentNullException(nameof(componentActivator));
+            }
+
             _serviceProvider = serviceProvider;
             _logger = loggerFactory.CreateLogger<Renderer>();
-
-            var componentActivator = serviceProvider.GetService<IComponentActivator>()
-                ?? DefaultComponentActivator.Instance;
             _componentFactory = new ComponentFactory(componentActivator);
         }
 
+        private static IComponentActivator GetComponentActivatorOrDefault(IServiceProvider serviceProvider)
+        {
+            return serviceProvider.GetService<IComponentActivator>()
+                ?? DefaultComponentActivator.Instance;
+        }
+
         /// <summary>
         /// Gets the <see cref="Microsoft.AspNetCore.Components.Dispatcher" /> associated with this <see cref="Renderer" />.
         /// </summary>

src/Components/Components/test/RendererTest.cs

@@ -3734,7 +3734,24 @@ namespace Microsoft.AspNetCore.Components.Test
         }
 
         [Fact]
-        public void CanUseCustomComponentActivator()
+        public void CanUseCustomComponentActivatorFromConstructorParameter()
+        {
+            // Arrange
+            var serviceProvider = new TestServiceProvider();
+            var componentActivator = new TestComponentActivator<MessageComponent>();
+            var renderer = new TestRenderer(serviceProvider, componentActivator);
+
+            // Act: Ask for TestComponent
+            var suppliedComponent = renderer.InstantiateComponent<TestComponent>();
+
+            // Assert: We actually receive MessageComponent
+            Assert.IsType<MessageComponent>(suppliedComponent);
+            Assert.Collection(componentActivator.RequestedComponentTypes,
+                requestedType => Assert.Equal(typeof(TestComponent), requestedType));
+        }
+
+        [Fact]
+        public void CanUseCustomComponentActivatorFromServiceProvider()
         {
             // Arrange
             var serviceProvider = new TestServiceProvider();

src/Components/Shared/test/TestRenderer.cs

@@ -29,6 +29,12 @@ namespace Microsoft.AspNetCore.Components.Test.Helpers
             Dispatcher = Dispatcher.CreateDefault();
         }
 
+        public TestRenderer(IServiceProvider serviceProvider, IComponentActivator componentActivator)
+            : base(serviceProvider, NullLoggerFactory.Instance, componentActivator)
+        {
+            Dispatcher = Dispatcher.CreateDefault();
+        }
+
         public override Dispatcher Dispatcher { get; }
 
         public Action OnExceptionHandled { get; set; }