[Fixes #1489] Support for named route in form tag helper

src/Microsoft.AspNet.Mvc.TagHelpers/FormTagHelper.cs

@@ -17,6 +17,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         private const string ActionAttributeName = "asp-action";
         private const string AntiForgeryAttributeName = "asp-anti-forgery";
         private const string ControllerAttributeName = "asp-controller";
+        private const string RouteAttributeName = "asp-route";
         private const string RouteAttributePrefix = "asp-route-";
         private const string HtmlActionAttributeName = "action";
 
@@ -47,6 +48,15 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         [HtmlAttributeName(AntiForgeryAttributeName)]
         public bool? AntiForgery { 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; }
+
         /// <inheritdoc />
         /// <remarks>
         /// Does nothing if user provides an <c>action</c> attribute and <see cref="AntiForgery"/> is <c>null</c> or
@@ -64,7 +74,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             // If "action" is already set, it means the user is attempting to use a normal <form>.
             if (output.Attributes.ContainsKey(HtmlActionAttributeName))
             {
-                if (Action != null || Controller != null || routePrefixedAttributes.Any())
+                if (Action != null || Controller != null || Route != null || routePrefixedAttributes.Any())
                 {
                     // User also specified bound attributes we cannot use.
                     throw new InvalidOperationException(
@@ -73,6 +83,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
                             HtmlActionAttributeName,
                             ActionAttributeName,
                             ControllerAttributeName,
+                            RouteAttributeName,
                             RouteAttributePrefix));
                 }
 
@@ -82,13 +93,38 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             }
             else
             {
+                TagBuilder tagBuilder;
                 var routeValues = GetRouteValues(output, routePrefixedAttributes);
-                var tagBuilder = Generator.GenerateForm(ViewContext,
+                if (Route == null)
-                                                        Action,
+                {
-                                                        Controller,
+                    tagBuilder = Generator.GenerateForm(
-                                                        routeValues,
+                        ViewContext,
-                                                        method: null,
+                        Action,
-                                                        htmlAttributes: null);
+                        Controller,
+                        routeValues,
+                        method: null,
+                        htmlAttributes: null);
+                }
+                else if (Action != null || Controller != null)
+                {
+                    // Route and Action or Controller were specified. Can't determine the action attribute.
+                    throw new InvalidOperationException(
+                        Resources.FormatFormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified(
+                            "<form>",
+                            RouteAttributeName,
+                            ActionAttributeName,
+                            ControllerAttributeName,
+                            HtmlActionAttributeName));
+                }
+                else
+                {
+                    tagBuilder = Generator.GenerateRouteForm(
+                        ViewContext,
+                        Route,
+                        routeValues,
+                        method: null,
+                        htmlAttributes: null);
+                }
 
                 if (tagBuilder != null)
                 {

src/Microsoft.AspNet.Mvc.TagHelpers/Properties/Resources.Designer.cs

@@ -43,7 +43,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{4}' or an '{2}' or '{3}' attribute.
+        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{5}' or an '{2}' or '{3}' or '{4}' attribute.
         /// </summary>
         internal static string FormTagHelper_CannotOverrideAction
         {
@@ -51,11 +51,11 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
         }
 
         /// <summary>
-        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{4}' or an '{2}' or '{3}' attribute.
+        /// Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{5}' or an '{2}' or '{3}' or '{4}' attribute.
         /// </summary>
-        internal static string FormatFormTagHelper_CannotOverrideAction(object p0, object p1, object p2, object p3, object p4)
+        internal static string FormatFormTagHelper_CannotOverrideAction(object p0, object p1, object p2, object p3, object p4, object p5)
         {
-            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotOverrideAction"), p0, p1, p2, p3, p4);
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotOverrideAction"), p0, p1, p2, p3, p4, p5);
         }
 
         /// <summary>
@@ -138,6 +138,22 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             return string.Format(CultureInfo.CurrentCulture, GetString("TagHelperOutput_AttributeDoesNotExist"), p0, p1);
         }
 
+        /// <summary>
+        /// Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
+        /// </summary>
+        internal static string FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified
+        {
+            get { return GetString("FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified"); }
+        }
+
+        /// <summary>
+        /// Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.
+        /// </summary>
+        internal static string FormatFormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified(object p0, object p1, object p2, object p3, object p4)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified"), p0, p1, p2, p3, p4);
+        }
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

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

@@ -124,7 +124,7 @@
     <value>Cannot override the '{8}' attribute for {0}. An {0} with a specified '{8}' must not have attributes starting with '{7}' or an '{1}', '{2}', '{3}', '{4}', '{5}', or '{6}' attribute.</value>
   </data>
   <data name="FormTagHelper_CannotOverrideAction" xml:space="preserve">
-    <value>Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{4}' or an '{2}' or '{3}' attribute.</value>
+    <value>Cannot override the '{1}' attribute for {0}. A {0} with a specified '{1}' must not have attributes starting with '{5}' or an '{2}' or '{3}' or '{4}' attribute.</value>
   </data>
   <data name="InputTagHelper_InvalidExpressionResult" xml:space="preserve">
     <value>Unexpected '{1}' expression result type '{2}' for {0}. '{1}' must be of type '{3}' if '{4}' is '{5}'.</value>
@@ -141,4 +141,7 @@
   <data name="TagHelperOutput_AttributeDoesNotExist" xml:space="preserve">
     <value>The attribute '{0}' does not exist in the {1}.</value>
   </data>
+  <data name="FormTagHelper_CannotDetermineActionWithRouteAndActionOrControllerSpecified" xml:space="preserve">
+    <value>Cannot determine an '{4}' attribute for {0}. A {0} with a specified '{1}' must not have an '{2}' or '{3}' attribute.</value>
+  </data>
 </root>

test/Microsoft.AspNet.Mvc.TagHelpers.Test/FormTagHelperTest.cs

@@ -252,11 +252,65 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal("form", output.TagName);
             Assert.False(output.SelfClosing);
             Assert.Empty(output.Attributes);
+            Assert.Empty(output.PreElement.GetContent());
             Assert.Empty(output.PreContent.GetContent());
             Assert.True(output.Content.IsEmpty);
             Assert.Empty(output.PostContent.GetContent());
         }
 
+        [Fact]
+        public async Task ProcessAsync_CallsIntoGenerateRouteFormWithExpectedParameters()
+        {
+            // Arrange
+            var viewContext = CreateViewContext();
+            var context = new TagHelperContext(
+                allAttributes: new Dictionary<string, object>(),
+                items: new Dictionary<object, object>(),
+                uniqueId: "test",
+                getChildContentAsync: () =>
+                {
+                    var tagHelperContent = new DefaultTagHelperContent();
+                    tagHelperContent.SetContent("Something");
+                    return Task.FromResult<TagHelperContent>(tagHelperContent);
+                });
+            var output = new TagHelperOutput(
+                "form",
+                attributes: new Dictionary<string, object>
+                {
+                    { "asp-route-foo", "bar" }
+                });
+            var generator = new Mock<IHtmlGenerator>(MockBehavior.Strict);
+            generator
+                .Setup(mock => mock.GenerateRouteForm(
+                    viewContext,
+                    "Default",
+                    It.Is<Dictionary<string, object>>(m => string.Equals(m["foo"], "bar")),
+                    null,
+                    null))
+                .Returns(new TagBuilder("form", new CommonTestEncoder()))
+                .Verifiable();
+            var formTagHelper = new FormTagHelper
+            {
+                AntiForgery = false,
+                Route = "Default",
+                Generator = generator.Object,
+                ViewContext = viewContext,
+            };
+
+            // Act & Assert
+            await formTagHelper.ProcessAsync(context, output);
+            generator.Verify();
+
+            Assert.Equal("form", output.TagName);
+            Assert.False(output.SelfClosing);
+            Assert.Empty(output.Attributes);
+            Assert.Empty(output.PreElement.GetContent());
+            Assert.Empty(output.PreContent.GetContent());
+            Assert.True(output.Content.IsEmpty);
+            Assert.Empty(output.PostContent.GetContent());
+            Assert.Empty(output.PostElement.GetContent());
+        }
+
         [Theory]
         [InlineData(true, "<input />")]
         [InlineData(false, "")]
@@ -333,7 +387,7 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
 
             var expectedErrorMessage = "Cannot override the 'action' attribute for <form>. A <form> with a specified " +
                                        "'action' must not have attributes starting with 'asp-route-' or an " +
-                                       "'asp-action' or 'asp-controller' attribute.";
+                                       "'asp-action' or 'asp-controller' or 'asp-route' attribute.";
 
             // Act & Assert
             var ex = await Assert.ThrowsAsync<InvalidOperationException>(
@@ -342,6 +396,30 @@ namespace Microsoft.AspNet.Mvc.TagHelpers
             Assert.Equal(expectedErrorMessage, ex.Message);
         }
 
+        [Theory]
+        [InlineData("Action")]
+        [InlineData("Controller")]
+        public async Task ProcessAsync_ThrowsIfRouteAndActionOrControllerProvided(string propertyName)
+        {
+            // Arrange
+            var formTagHelper = new FormTagHelper
+            {
+                Route = "Default",
+            };
+            typeof(FormTagHelper).GetProperty(propertyName).SetValue(formTagHelper, "Home");
+            var output = new TagHelperOutput(
+                "form",
+                attributes: new Dictionary<string, object>());
+            var expectedErrorMessage = "Cannot determine an 'action' attribute for <form>. A <form> with a specified " +
+                "'asp-route' must not have an 'asp-action' or 'asp-controller' attribute.";
+
+            // Act & Assert
+            var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+                () => formTagHelper.ProcessAsync(context: null, output: output));
+
+            Assert.Equal(expectedErrorMessage, ex.Message);
+        }
+
         private static ViewContext CreateViewContext()
         {
             var actionContext = new ActionContext(