Add HtmlAttributeNameAttribute for TagHelpers.

- Added the ability to override the HTML attribute name for TagHelper properties.
- Tested functionality of overriding the attribute name target and inheriting the attribute name.

#121

src/Microsoft.AspNet.Razor.Runtime/Properties/Resources.Designer.cs

@@ -94,6 +94,22 @@ namespace Microsoft.AspNet.Razor.Runtime
             return string.Format(CultureInfo.CurrentCulture, GetString("TagNameAttribute_AdditionalTagsCannotContainNull"), p0);
         }
 
+        /// <summary>
+        /// The value cannot be null or empty.
+        /// </summary>
+        internal static string ArgumentCannotBeNullOrEmpty
+        {
+            get { return GetString("ArgumentCannotBeNullOrEmpty"); }
+        }
+
+        /// <summary>
+        /// The value cannot be null or empty.
+        /// </summary>
+        internal static string FormatArgumentCannotBeNullOrEmpty()
+        {
+            return GetString("ArgumentCannotBeNullOrEmpty");
+        }
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

src/Microsoft.AspNet.Razor.Runtime/Resources.resx

@@ -134,4 +134,7 @@
   <data name="TagNameAttribute_AdditionalTagsCannotContainNull" xml:space="preserve">
     <value>Parameter {0} must not contain null tag names.</value>
   </data>
+  <data name="ArgumentCannotBeNullOrEmpty" xml:space="preserve">
+    <value>The value cannot be null or empty.</value>
+  </data>
 </root>

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/HtmlAttributeNameAttribute.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Open Technologies, Inc. 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.Razor.Runtime.TagHelpers
+{
+    /// <summary>
+    /// Used to override an <see cref="ITagHelper"/> property's HTML attribute name.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
+    public sealed class HtmlAttributeNameAttribute : Attribute
+    {
+        /// <summary>
+        /// Instantiates a new instance of the <see cref="HtmlAttributeNameAttribute"/> class.
+        /// </summary>
+        /// <param name="name">HTML attribute name for the associated property.</param>
+        public HtmlAttributeNameAttribute(string name)
+        {
+            if (string.IsNullOrEmpty(name))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(name));
+            }
+
+            Name = name;
+        }
+
+        /// <summary>
+        /// HTML attribute name of the associated property.
+        /// </summary>
+        public string Name { get; private set; }
+    }
+}

src/Microsoft.AspNet.Razor.Runtime/TagHelpers/TagHelperDescriptorFactory.cs

@@ -68,11 +68,14 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             return attributeDescriptors;
         }
 
-        // TODO: Make the HTML attribute name support names from a AttributeNameAttribute: 
-        // https://github.com/aspnet/Razor/issues/121
         private static TagHelperAttributeDescriptor ToAttributeDescriptor(PropertyInfo property)
         {
-            return new TagHelperAttributeDescriptor(property.Name, property);
+            var attributeNameAttribute = property.GetCustomAttribute<HtmlAttributeNameAttribute>(inherit: false);
+            var attributeName = attributeNameAttribute != null ? 
+                                attributeNameAttribute.Name : 
+                                property.Name;
+
+            return new TagHelperAttributeDescriptor(attributeName, property);
         }
 
         private static ContentBehavior GetContentBehavior(Type type)

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/CompleteTagHelperDescriptorComparer.cs

@@ -8,7 +8,7 @@ using Microsoft.Internal.Web.Utils;
 
 namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
-    public class CompleteTagHelperDescriptorComparer : TagHelperDescriptorComparer
+    public class CompleteTagHelperDescriptorComparer : TagHelperDescriptorComparer, IEqualityComparer<TagHelperDescriptor>
     {
         public new static readonly CompleteTagHelperDescriptorComparer Default =
             new CompleteTagHelperDescriptorComparer();
@@ -17,14 +17,14 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         {
         }
 
-        public new bool Equals(TagHelperDescriptor descriptorX, TagHelperDescriptor descriptorY)
+        bool IEqualityComparer<TagHelperDescriptor>.Equals(TagHelperDescriptor descriptorX, TagHelperDescriptor descriptorY)
         {
             return base.Equals(descriptorX, descriptorY) &&
                    descriptorX.Attributes.SequenceEqual(descriptorY.Attributes,
                                                         CompleteTagHelperAttributeDescriptorComparer.Default);
         }
 
-        public new int GetHashCode(TagHelperDescriptor descriptor)
+        int IEqualityComparer<TagHelperDescriptor>.GetHashCode(TagHelperDescriptor descriptor)
         {
             return HashCodeCombiner.Start()
                                    .Add(base.GetHashCode())

test/Microsoft.AspNet.Razor.Runtime.Test/TagHelpers/TagHelperDescriptorFactoryTest.cs

@@ -8,6 +8,85 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 {
     public class TagHelperDescriptorFactoryTest
     {
+        [Fact]
+        public void CreateDescriptor_OverridesAttributeNameFromAttribute()
+        {
+            // Arrange
+            var validProperty1 = typeof(OverriddenAttributeTagHelper).GetProperty(
+                nameof(OverriddenAttributeTagHelper.ValidAttribute1));
+            var validProperty2 = typeof(OverriddenAttributeTagHelper).GetProperty(
+                nameof(OverriddenAttributeTagHelper.ValidAttribute2));
+            var expectedDescriptors = new[] {
+                new TagHelperDescriptor(
+                    "OverriddenAttribute",
+                    typeof(OverriddenAttributeTagHelper).FullName,
+                    ContentBehavior.None,
+                    new[] {
+                        new TagHelperAttributeDescriptor("SomethingElse", validProperty1),
+                        new TagHelperAttributeDescriptor("Something-Else", validProperty2)
+                    })
+            };
+
+            // Act
+            var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(OverriddenAttributeTagHelper));
+
+            // Assert
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
+        }
+
+        [Fact]
+        public void CreateDescriptor_DoesNotInheritOverridenAttributeName()
+        {
+            // Arrange
+            var validProperty1 = typeof(InheritedOverriddenAttributeTagHelper).GetProperty(
+                nameof(InheritedOverriddenAttributeTagHelper.ValidAttribute1));
+            var validProperty2 = typeof(InheritedOverriddenAttributeTagHelper).GetProperty(
+                nameof(InheritedOverriddenAttributeTagHelper.ValidAttribute2));
+            var expectedDescriptors = new[] {
+                new TagHelperDescriptor(
+                    "InheritedOverriddenAttribute",
+                    typeof(InheritedOverriddenAttributeTagHelper).FullName,
+                    ContentBehavior.None,
+                    new[] {
+                        new TagHelperAttributeDescriptor(nameof(InheritedOverriddenAttributeTagHelper.ValidAttribute1),
+                                                         validProperty1),
+                        new TagHelperAttributeDescriptor("Something-Else", validProperty2)
+                    })
+            };
+
+            // Act
+            var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(InheritedOverriddenAttributeTagHelper));
+
+            // Assert
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
+        }
+
+        [Fact]
+        public void CreateDescriptor_AllowsOverridenAttributeNameOnUnimplementedVirtual()
+        {
+            // Arrange
+            var validProperty1 = typeof(InheritedNotOverriddenAttributeTagHelper).GetProperty(
+                nameof(InheritedNotOverriddenAttributeTagHelper.ValidAttribute1));
+            var validProperty2 = typeof(InheritedNotOverriddenAttributeTagHelper).GetProperty(
+                nameof(InheritedNotOverriddenAttributeTagHelper.ValidAttribute2));
+            var expectedDescriptors = new[] {
+                new TagHelperDescriptor(
+                    "InheritedNotOverriddenAttribute",
+                    typeof(InheritedNotOverriddenAttributeTagHelper).FullName,
+                    ContentBehavior.None,
+                    new[] {
+                        new TagHelperAttributeDescriptor("SomethingElse", validProperty1),
+                        new TagHelperAttributeDescriptor("Something-Else", validProperty2)
+                    })
+            };
+
+            // Act
+            var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(InheritedNotOverriddenAttributeTagHelper));
+
+            // Assert
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
+        }
+
         [Fact]
         public void CreateDescriptor_BuildsDescriptorsFromSimpleTypes()
         {
@@ -19,7 +98,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -41,7 +120,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -62,7 +141,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -84,7 +163,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -107,7 +186,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -124,7 +203,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -142,7 +221,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -171,7 +250,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(MultiTagTagHelper));
 
             // Assert
-            Assert.Equal(descriptors, expectedDescriptors, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -192,7 +271,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
 
             // Assert
             var descriptor = Assert.Single(descriptors);
-            Assert.Equal(descriptor, expectedDescriptor, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptor, descriptor, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -208,7 +287,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(DuplicateTagNameTagHelper));
 
             // Assert
-            Assert.Equal(descriptors, expectedDescriptors, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -225,7 +304,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(OverrideNameTagHelper));
 
             // Assert
-            Assert.Equal(descriptors, expectedDescriptors, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [Fact]
@@ -242,7 +321,7 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
             var descriptors = TagHelperDescriptorFactory.CreateDescriptors(typeof(MultipleAttributeTagHelper));
 
             // Assert
-            Assert.Equal(descriptors, expectedDescriptors, CompleteTagHelperDescriptorComparer.Default);
+            Assert.Equal(expectedDescriptors, descriptors, CompleteTagHelperDescriptorComparer.Default);
         }
 
         [ContentBehavior(ContentBehavior.Append)]
@@ -283,5 +362,23 @@ namespace Microsoft.AspNet.Razor.Runtime.TagHelpers
         private class InheritedSingleAttributeTagHelper : SingleAttributeTagHelper
         {
         }
+
+        private class OverriddenAttributeTagHelper
+        {
+            [HtmlAttributeName("SomethingElse")]
+            public virtual string ValidAttribute1 { get; set; }
+
+            [HtmlAttributeName("Something-Else")]
+            public string ValidAttribute2 { get; set; }
+        }
+
+        private class InheritedOverriddenAttributeTagHelper : OverriddenAttributeTagHelper
+        {
+            public override string ValidAttribute1 { get; set; }
+        }
+
+        private class InheritedNotOverriddenAttributeTagHelper : OverriddenAttributeTagHelper
+        {
+        }
     }
 }