Part of #2151 - Remove [Activate] from ViewComponents

This change removes [Activate] from ViewComponents. Accessing context
should be done through [ViewComponentContext]. Accessing services should
be done though constructor injection.

src/Microsoft.AspNet.Mvc.Core/ViewComponents/DefaultViewComponentActivator.cs

@@ -3,40 +3,38 @@
 
 using System;
 using System.Collections.Concurrent;
-using System.Collections.Generic;
 using System.Reflection;
-using Microsoft.AspNet.Mvc.Rendering;
-using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Mvc.ViewComponents
 {
     /// <summary>
-    /// Represents the <see cref="IViewComponentActivator"/> that is registered by default.
+    /// A default implemented of <see cref="IViewComponentActivator"/>.
     /// </summary>
     public class DefaultViewComponentActivator : IViewComponentActivator
     {
-        private readonly Func<Type, PropertyActivator<ViewContext>[]> _getPropertiesToActivate;
-        private readonly IDictionary<Type, Func<ViewContext, object>> _valueAccessorLookup;
-        private readonly ConcurrentDictionary<Type, PropertyActivator<ViewContext>[]> _injectActions;
+        private readonly Func<Type, PropertyActivator<ViewComponentContext>[]> _getPropertiesToActivate;
+        private readonly ConcurrentDictionary<Type, PropertyActivator<ViewComponentContext>[]> _injectActions;
 
         /// <summary>
         /// Initializes a new instance of <see cref="DefaultViewComponentActivator"/> class.
         /// </summary>
         public DefaultViewComponentActivator()
         {
-            _valueAccessorLookup = CreateValueAccessorLookup();
-            _injectActions = new ConcurrentDictionary<Type, PropertyActivator<ViewContext>[]>();
+            _injectActions = new ConcurrentDictionary<Type, PropertyActivator<ViewComponentContext>[]>();
             _getPropertiesToActivate = type =>
-                PropertyActivator<ViewContext>.GetPropertiesToActivate(
-                    type, typeof(ActivateAttribute), CreateActivateInfo);
+                PropertyActivator<ViewComponentContext>.GetPropertiesToActivate(
+                    type,
+                    typeof(ViewComponentContextAttribute),
+                    CreateActivateInfo);
         }
 
         /// <inheritdoc />
-        public virtual void Activate([NotNull] object viewComponent, [NotNull] ViewContext context)
+        public virtual void Activate([NotNull] object viewComponent, [NotNull] ViewComponentContext context)
         {
-            var propertiesToActivate = _injectActions.GetOrAdd(viewComponent.GetType(),
-                                                               _getPropertiesToActivate);
+            var propertiesToActivate = _injectActions.GetOrAdd(
+                viewComponent.GetType(),
+                _getPropertiesToActivate);
 
             for (var i = 0; i < propertiesToActivate.Length; i++)
             {
@@ -45,44 +43,9 @@ public virtual void Activate([NotNull] object viewComponent, [NotNull] ViewConte
             }
         }
 
-        /// <summary>
-        /// Creates a lookup dictionary for the values to be activated.
-        /// </summary>
-        /// <returns>Returns a readonly dictionary of the values corresponding to the types.</returns>
-        protected virtual IDictionary<Type, Func<ViewContext, object>> CreateValueAccessorLookup()
-        {
-            return new Dictionary<Type, Func<ViewContext, object>>
-            {
-                { typeof(ViewContext), (context) => context },
-                {
-                    typeof(ViewDataDictionary),
-                    (context) =>
-                    {
-                        return new ViewDataDictionary(context.ViewData);
-                    }
-                }
-            };
-        }
-
-        private PropertyActivator<ViewContext> CreateActivateInfo(PropertyInfo property)
+        private PropertyActivator<ViewComponentContext> CreateActivateInfo(PropertyInfo property)
         {
-            Func<ViewContext, object> valueAccessor;
-            if (!_valueAccessorLookup.TryGetValue(property.PropertyType, out valueAccessor))
-            {
-                valueAccessor = (viewContext) =>
-                {
-                    var serviceProvider = viewContext.HttpContext.RequestServices;
-                    var service = serviceProvider.GetRequiredService(property.PropertyType);
-                    if (typeof(ICanHasViewContext).IsAssignableFrom(property.PropertyType))
-                    {
-                        ((ICanHasViewContext)service).Contextualize(viewContext);
-                    }
-
-                    return service;
-                };
-            }
-
-            return new PropertyActivator<ViewContext>(property, valueAccessor);
+            return new PropertyActivator<ViewComponentContext>(property, context => context);
         }
     }
 }

src/Microsoft.AspNet.Mvc.Core/ViewComponents/DefaultViewComponentInvoker.cs

@@ -80,7 +80,7 @@ private object CreateComponent([NotNull] ViewComponentContext context)
             var component = _typeActivatorCache.CreateInstance<object>(
                 _serviceProvider, 
                 context.ViewComponentDescriptor.Type);
-            _viewComponentActivator.Activate(component, context.ViewContext);
+            _viewComponentActivator.Activate(component, context);
             return component;
         }
 

src/Microsoft.AspNet.Mvc.Core/ViewComponents/IViewComponentActivator.cs

@@ -12,7 +12,9 @@ public interface IViewComponentActivator
         /// When implemented in a type, activates an instantiated ViewComponent.
         /// </summary>
         /// <param name="viewComponent">The ViewComponent to activate.</param>
-        /// <param name="context">The <see cref="ViewContext"/> for the executing <see cref="ViewComponent"/>.</param>
-        void Activate(object viewComponent, ViewContext context);
+        /// <param name="context">
+        /// The <see cref="ViewComponentContext"/> for the executing <see cref="ViewComponent"/>.
+        /// </param>
+        void Activate(object viewComponent, ViewComponentContext context);
     }
 }

src/Microsoft.AspNet.Mvc.Core/ViewComponents/ViewComponent.cs

@@ -6,7 +6,9 @@
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Mvc.ModelBinding;
 using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.Mvc.ViewComponents;
 using Microsoft.AspNet.Routing;
+using Microsoft.Framework.DependencyInjection;
 using Microsoft.Framework.Internal;
 using Newtonsoft.Json;
 
@@ -18,9 +20,10 @@ namespace Microsoft.AspNet.Mvc
     [ViewComponent]
     public abstract class ViewComponent
     {
+        private IUrlHelper _url;
         private dynamic _viewBag;
-        private ViewContext _viewContext;
-        private ViewDataDictionary _viewData;
+        private ViewComponentContext _viewComponentContext;
+        private ICompositeViewEngine _viewEngine;
 
         /// <summary>
         /// Gets the <see cref="HttpContext"/>.
@@ -96,63 +99,94 @@ public ModelStateDictionary ModelState
         /// <summary>
         /// Gets or sets the <see cref="IUrlHelper"/>.
         /// </summary>
-        [Activate]
-        public IUrlHelper Url { get; set; }
+        public IUrlHelper Url
+        {
+            get
+            {
+                if (_url == null)
+                {
+                    // May be null in unit-testing scenarios.
+                    var services = ViewComponentContext?.ViewContext?.HttpContext?.RequestServices;
+                    _url = services?.GetRequiredService<IUrlHelper>();
+                }
 
-        /// <summary>
-        /// Gets or sets the <see cref="ViewContext"/>.
-        /// </summary>
-        [Activate]
-        public ViewContext ViewContext
+                return _url;
+            }
+
+            [param: NotNull]
+            set
+            {
+                _url = value;
+            }
+        }
+
+        [ViewComponentContext]
+        public ViewComponentContext ViewComponentContext
         {
             get
             {
-                if (_viewContext == null)
+                if (_viewComponentContext == null)
                 {
-                    // This should run only for the ViewComponent unit test scenarios
-                    _viewContext = new ViewContext();
+                    _viewComponentContext = new ViewComponentContext();
                 }
 
-                return _viewContext;
+                return _viewComponentContext;
             }
 
             [param: NotNull]
             set
             {
-                _viewContext = value;
+                _viewComponentContext = value;
             }
         }
 
         /// <summary>
-        /// Gets or sets the <see cref="ViewDataDictionary"/>.
+        /// Gets the <see cref="ViewContext"/>.
         /// </summary>
         [Activate]
+        public ViewContext ViewContext
+        {
+            get
+            {
+                return ViewComponentContext?.ViewContext;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the <see cref="ViewDataDictionary"/>.
+        /// </summary>
         public ViewDataDictionary ViewData
         {
             get
             {
-                if (_viewData == null)
+                return ViewComponentContext?.ViewData;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the <see cref="ICompositeViewEngine"/>.
+        /// </summary>
+        public ICompositeViewEngine ViewEngine
+        {
+            get
+            {
+                if (_viewEngine == null)
                 {
-                    // This should run only for the ViewComponent unit test scenarios
-                    _viewData = new ViewDataDictionary(ViewContext.ViewData);
+                    // May be null in unit-testing scenarios.
+                    var services = ViewComponentContext.ViewContext?.HttpContext?.RequestServices;
+                    _viewEngine = services?.GetRequiredService<ICompositeViewEngine>();
                 }
 
-                return _viewData;
+                return _viewEngine;
             }
 
             [param: NotNull]
             set
             {
-                _viewData = value;
+                _viewEngine = value;
             }
         }
 
-        /// <summary>
-        /// Gets or sets the <see cref="ICompositeViewEngine"/>.
-        /// </summary>
-        [Activate]
-        public ICompositeViewEngine ViewEngine { get; set; }
-
         /// <summary>
         /// Returns a result which will render HTML encoded text.
         /// </summary>

src/Microsoft.AspNet.Mvc.Core/ViewComponents/ViewComponentContext.cs

@@ -12,6 +12,22 @@ namespace Microsoft.AspNet.Mvc
     /// </summary>
     public class ViewComponentContext
     {
+        /// <summary>
+        /// Creates a new <see cref="ViewComponentContext"/>.
+        /// </summary>
+        /// <remarks>
+        /// The default constructor is provided for unit test purposes only.
+        /// </remarks>
+        public ViewComponentContext()
+        {
+            ViewComponentDescriptor = new ViewComponentDescriptor();
+            Arguments = new object[0];
+            ViewContext = new ViewContext();
+            Writer = TextWriter.Null;
+
+            ViewData = ViewContext.ViewData;
+        }
+
         /// <summary>
         /// Creates a new <see cref="ViewComponentContext"/>.
         /// </summary>
@@ -31,30 +47,54 @@ public ViewComponentContext(
             Arguments = arguments;
             ViewContext = viewContext;
             Writer = writer;
+
+            ViewData = ViewContext.ViewData;
         }
 
         /// <summary>
-        /// Gets the View Component arguments. 
+        /// Gets or sets the View Component arguments. 
         /// </summary>
-        public object[] Arguments { get; }
+        /// <remarks>
+        /// The property setter is provided for unit test purposes only.
+        /// </remarks>
+        public object[] Arguments { get; set; }
+
+        /// <summary>
+        /// Gets or sets the <see cref="ViewComponentDescriptor"/> for the View Component being invoked.
+        /// </summary>
+        /// <remarks>
+        /// The property setter is provided for unit test purposes only.
+        /// </remarks>
+        public ViewComponentDescriptor ViewComponentDescriptor { get; set; }
 
         /// <summary>
-        /// Gets the <see cref="ViewComponentDescriptor"/> for the View Component being invoked.
+        /// Gets or sets the <see cref="ViewContext"/>.
         /// </summary>
-        public ViewComponentDescriptor ViewComponentDescriptor { get; }
+        /// <remarks>
+        /// The property setter is provided for unit test purposes only.
+        /// </remarks>
+        public ViewContext ViewContext { get; set; }
 
         /// <summary>
-        /// Gets the <see cref="ViewContext"/>.
+        /// Gets or sets the <see cref="ViewDataDictionary"/>.
         /// </summary>
-        public ViewContext ViewContext { get; }
+        /// <remarks>
+        /// The property setter is provided for unit test purposes only.
+        /// </remarks>
+        public ViewDataDictionary ViewData { get; set; }
 
         /// <summary>
-        /// Gets the <see cref="TextWriter"/> for writing output.
+        /// Gets or sets the <see cref="TextWriter"/> for writing output.
         /// </summary>
         /// <remarks>
+        /// <para>
+        /// The property setter is provided for unit test purposes only.
+        /// </para>
+        /// <para>
         /// <see cref="IViewComponentHelper.Invoke(string, object[])"/> or a similar overload is used to invoke the
         /// View Component, then <see cref="Writer"/> will be different than <see cref="ViewContext.Writer"/>.
+        /// </para>
         /// </remarks>
-        public TextWriter Writer { get; }
+        public TextWriter Writer { get; set; }
     }
 }

src/Microsoft.AspNet.Mvc.Core/ViewComponents/ViewComponentContextAttribute.cs

@@ -0,0 +1,12 @@
+// 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.AspNet.Mvc.ViewComponents
+{
+    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+    public class ViewComponentContextAttribute : Attribute
+    {
+    }
+}