Removed the TypeActivator from TagHelper creation.

- We now new up TagHelper's, requiring them to have parameterless constructors.
- Added test to validate throwing.
- Removed existing tests that expected the constructor injection behavior.

#1303

Author: N. Taylor Mullen

src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs

@@ -25,7 +25,6 @@ public abstract class RazorPage : IRazorPage
         private readonly Stack<TextWriter> _writerScopes;
         private TextWriter _originalWriter;
         private IUrlHelper _urlHelper;
-        private ITypeActivator _typeActivator;
         private ITagHelperActivator _tagHelperActivator;
         private bool _renderedBody;
 
@@ -114,19 +113,6 @@ public dynamic ViewBag
         /// <inheritdoc />
         public abstract Task ExecuteAsync();
 
-        private ITypeActivator TypeActivator
-        {
-            get
-            {
-                if(_typeActivator == null)
-                {
-                    _typeActivator = ViewContext.HttpContext.RequestServices.GetService<ITypeActivator>();
-                }
-
-                return _typeActivator;
-            }
-        }
-
         private ITagHelperActivator TagHelperActivator
         {
             get
@@ -139,19 +125,17 @@ private ITagHelperActivator TagHelperActivator
                 return _tagHelperActivator;
             }
         }
-
         /// <summary>
         /// Creates and activates a <see cref="ITagHelper"/>.
         /// </summary>
         /// <typeparam name="TTagHelper">A <see cref="ITagHelper"/> type.</typeparam>
         /// <returns>The activated <see cref="ITagHelper"/>.</returns>
         /// <remarks>
-        /// If the <see cref= "ITagHelper" /> implements <see cref="ICanHasViewContext"/> the 
-        /// <see cref="ICanHasViewContext.Contextualize(ViewContext)"/> method is called with <see cref="ViewContext"/>.
+        /// <typeparamref name="TTagHelper"/> must have a parameterless constructor.
         /// </remarks>
-        public TTagHelper CreateTagHelper<TTagHelper>() where TTagHelper : ITagHelper
+        public TTagHelper CreateTagHelper<TTagHelper>() where TTagHelper : ITagHelper, new()
         {
-            var tagHelper = TypeActivator.CreateInstance<TTagHelper>(ViewContext.HttpContext.RequestServices);
+            var tagHelper = new TTagHelper();
 
             TagHelperActivator.Activate(tagHelper, ViewContext);
 

test/Microsoft.AspNet.Mvc.Razor.Test/RazorPageCreateTagHelperTest.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Globalization;
 using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
@@ -31,43 +32,16 @@ public void CreateTagHelper_CreatesProvidedTagHelperType()
         }
 
         [Fact]
-        public void CreateTagHelper_ActivatesProvidedTagHelperType_Constructor()
+        public void CreateTagHelper_ActivatesProvidedTagHelperType()
         {
             // Arrange
             var instance = CreateTestRazorPage();
 
             // Act
-            var tagHelper = instance.CreateTagHelper<ConstructorServiceTagHelper>();
-
-            // Assert
-            Assert.NotNull(tagHelper.PassedInService);
-        }
-
-        [Fact]
-        public void CreateTagHelper_ActivatesProvidedTagHelperType_Property()
-        {
-            // Arrange
-            var instance = CreateTestRazorPage();
-
-            // Act
-            var tagHelper = instance.CreateTagHelper<ActivateAttributeServiceTagHelper>();
-
-            // Assert
-            Assert.NotNull(tagHelper.ActivatedService);
-        }
-
-        [Fact]
-        public void CreateTagHelper_ActivatesProvidedTagHelperType_PropertyAndConstructor()
-        {
-            // Arrange
-            var instance = CreateTestRazorPage();
-
-            // Act
-            var tagHelper = instance.CreateTagHelper<AttributeConstructorServiceTagHelper>();
+            var tagHelper = instance.CreateTagHelper<ServiceTagHelper>();
 
             // Assert
             Assert.NotNull(tagHelper.ActivatedService);
-            Assert.NotNull(tagHelper.PassedInService);
         }
 
         [Fact]
@@ -94,7 +68,7 @@ public void CreateTagHelper_ProvidesTagHelperTypeWithViewContextAndActivates()
 
             // Assert
             Assert.NotNull(tagHelper.ViewContext);
-            Assert.NotNull(tagHelper.PassedInService);
+            Assert.NotNull(tagHelper.ActivatedService);
         }
 
         private static TestRazorPage CreateTestRazorPage()
@@ -138,35 +112,12 @@ private class NoServiceTagHelper : TagHelper
         {
         }
 
-        private class ConstructorServiceTagHelper : TagHelper
-        {
-            public MyService PassedInService { get; set; }
-
-            public ConstructorServiceTagHelper(MyService service)
-            {
-                PassedInService = service;
-            }
-        }
-
-        private class ActivateAttributeServiceTagHelper : TagHelper
+        private class ServiceTagHelper : TagHelper
         {
             [Activate]
             public MyService ActivatedService { get; set; }
         }
 
-        private class AttributeConstructorServiceTagHelper : TagHelper
-        {
-            [Activate]
-            public MyService ActivatedService { get; set; }
-
-            public MyService PassedInService { get; set; }
-
-            public AttributeConstructorServiceTagHelper(MyService service)
-            {
-                PassedInService = service;
-            }
-        }
-
         private class ViewContextTagHelper : TagHelper
         {
             [Activate]
@@ -175,12 +126,8 @@ private class ViewContextTagHelper : TagHelper
 
         private class ViewContextServiceTagHelper : ViewContextTagHelper
         {
-            public MyService PassedInService { get; set; }
-
-            public ViewContextServiceTagHelper(MyService service)
-            {
-                PassedInService = service;
-            }
+            [Activate]
+            public MyService ActivatedService { get; set; }
         }
 
         private class MyService