Add buttonTagHelper and submitTagHelper for formaction

src/Microsoft.AspNetCore.Mvc.TagHelpers/ButtonTagHelper.cs

@@ -0,0 +1,185 @@
+// 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;
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Mvc.Rendering;
+using Microsoft.AspNetCore.Mvc.Routing;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using Microsoft.AspNetCore.Routing;
+
+namespace Microsoft.AspNetCore.Mvc.TagHelpers
+{
+    /// <summary>
+    /// <see cref="ITagHelper"/> implementation targeting &lt;button&gt; elements.
+    /// </summary>
+    [HtmlTargetElement("button", Attributes = ActionAttributeName)]
+    [HtmlTargetElement("button", Attributes = ControllerAttributeName)]
+    [HtmlTargetElement("button", Attributes = AreaAttributeName)]
+    [HtmlTargetElement("button", Attributes = RouteAttributeName)]
+    [HtmlTargetElement("button", Attributes = RouteValuesDictionaryName)]
+    [HtmlTargetElement("button", Attributes = RouteValuesPrefix + "*")]
+    public class ButtonTagHelper : TagHelper
+    {
+        private const string ActionAttributeName = "asp-action";
+        private const string ControllerAttributeName = "asp-controller";
+        private const string AreaAttributeName = "asp-area";
+        private const string RouteAttributeName = "asp-route";
+        private const string RouteValuesDictionaryName = "asp-all-route-data";
+        private const string RouteValuesPrefix = "asp-route-";
+        private const string FormAction = "formaction";
+        private IDictionary<string, string> _routeValues;
+
+        /// <summary>
+        /// Creates a new <see cref="ButtonTagHelper"/>.
+        /// </summary>
+        /// <param name="urlHelperFactory">The <see cref="IUrlHelperFactory"/>.</param>
+        public ButtonTagHelper(IUrlHelperFactory urlHelperFactory)
+        {
+            UrlHelperFactory = urlHelperFactory;
+        }
+
+        /// <inheritdoc />
+        public override int Order => -1000;
+
+        /// <summary>
+        /// Gets or sets the <see cref="Rendering.ViewContext"/> for the current request.
+        /// </summary>
+        [HtmlAttributeNotBound]
+        [ViewContext]
+        public ViewContext ViewContext { get; set; }
+
+        protected IUrlHelperFactory UrlHelperFactory { get; }
+
+        /// <summary>
+        /// The name of the action method.
+        /// </summary>
+        [HtmlAttributeName(ActionAttributeName)]
+        public string Action { get; set; }
+
+        /// <summary>
+        /// The name of the controller.
+        /// </summary>
+        [HtmlAttributeName(ControllerAttributeName)]
+        public string Controller { get; set; }
+
+        /// <summary>
+        /// The name of the area.
+        /// </summary>
+        [HtmlAttributeName(AreaAttributeName)]
+        public string Area { get; set; }
+
+        /// <summary>
+        /// Name of the route.
+        /// </summary>
+        /// <remarks>
+        /// Must be <c>null</c> if <see cref="Action"/> or <see cref="Controller"/> is non-<c>null</c>.
+        /// </remarks>
+        [HtmlAttributeName(RouteAttributeName)]
+        public string Route { get; set; }
+
+        /// <summary>
+        /// Additional parameters for the route.
+        /// </summary>
+        [HtmlAttributeName(RouteValuesDictionaryName, DictionaryAttributePrefix = RouteValuesPrefix)]
+        public IDictionary<string, string> RouteValues
+        {
+            get
+            {
+                if (_routeValues == null)
+                {
+                    _routeValues = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+                }
+
+                return _routeValues;
+            }
+            set
+            {
+                _routeValues = value;
+            }
+        }
+
+        /// <inheritdoc />
+        /// <remarks>Does nothing if user provides an <c>formaction</c> attribute.</remarks>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if <c>formaction</c> attribute is provided and <see cref="Action"/>, <see cref="Controller"/>,
+        /// or <see cref="Route"/> are non-<c>null</c> or if the user provided <c>asp-route-*</c> attributes.
+        /// Also thrown if <see cref="Route"/> and one or both of <see cref="Action"/> and <see cref="Controller"/>
+        /// are non-<c>null</c>
+        /// </exception>
+        public override void Process(TagHelperContext context, TagHelperOutput output)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (output == null)
+            {
+                throw new ArgumentNullException(nameof(output));
+            }
+
+            // If "formaction" is already set, it means the user is attempting to use a normal button.
+            if (output.Attributes.ContainsName(FormAction))
+            {
+                if (Action != null || Controller != null || Area != null || Route != null || RouteValues.Count != 0)
+                {
+                    // User specified a formaction and one of the bound attributes; can't determine the formaction attribute.
+                    throw new InvalidOperationException(
+                        Resources.FormatButtonTagHelper_CannotOverrideFormAction(
+                            "<button>",
+                            ActionAttributeName,
+                            ControllerAttributeName,
+                            AreaAttributeName,
+                            RouteAttributeName,
+                            RouteValuesPrefix,
+                            FormAction));
+                }
+            }
+            else
+            {
+                RouteValueDictionary routeValues = null;
+                if (_routeValues != null && _routeValues.Count > 0)
+                {
+                    routeValues = new RouteValueDictionary(_routeValues);
+                }
+
+                if (Area != null)
+                {
+                    if (routeValues == null)
+                    {
+                        routeValues = new RouteValueDictionary();
+                    }
+
+                    // Unconditionally replace any value from asp-route-area. 
+                    routeValues["area"] = Area;
+                }
+
+                if (Route == null)
+                {
+                    var urlHelper = UrlHelperFactory.GetUrlHelper(ViewContext);
+                    var url = urlHelper.Action(Action, Controller, routeValues);
+                    output.Attributes.SetAttribute(FormAction, url);
+                }
+                else if (Action != null || Controller != null)
+                {
+                    // Route and Action or Controller were specified. Can't determine the formaction attribute.
+                    throw new InvalidOperationException(
+                        Resources.FormatButtonTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified(
+                            "<button>",
+                            RouteAttributeName,
+                            ActionAttributeName,
+                            ControllerAttributeName,
+                            FormAction));
+                }
+                else
+                {
+                    var urlHelper = UrlHelperFactory.GetUrlHelper(ViewContext);
+                    var url = urlHelper.RouteUrl(Route, routeValues);
+                    output.Attributes.SetAttribute(FormAction, url);
+                }
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.TagHelpers/Resources.resx

@@ -147,4 +147,16 @@
   <data name="PropertyOfTypeCannotBeNull" xml:space="preserve">
     <value>The '{0}' property of '{1}' must not be null.</value>
   </data>
+  <data name="ButtonTagHelper_CannotOverrideFormAction" xml:space="preserve">
+    <value>Cannot override the '{6}' attribute for {0}. A {0} with a specified '{6}' must not have attributes starting with '{5}' or an '{1}', '{2}', '{3}', or '{4}' attribute.</value>
+  </data>
+  <data name="ButtonTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified" xml:space="preserve">
+    <value>Cannot determine a '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
+  </data>
+  <data name="SubmitTagHelper_CannotDetermineFormActionRouteActionOrControllerSpecified" xml:space="preserve">
+    <value>Cannot determine a '{4}' attribute for {0}. An {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
+  </data>
+  <data name="SubmitTagHelper_CannotOverrideFormAction" xml:space="preserve">
+    <value>Cannot override the '{6}' attribute for {0}. An {0} with a specified '{6}' must not have attributes starting with '{5}' or an '{1}', '{2}', '{3}', or '{4}' attribute.</value>
+  </data>
 </root>