Move TagHelperBinding out of Legacy.

- Added additional properties to the class to make it more production ready.

#1092

src/Microsoft.AspNetCore.Razor.Language/TagHelperBinder.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Microsoft.AspNetCore.Razor.Language.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
@@ -97,7 +96,12 @@ public TagHelperBinding GetBinding(
                 return null;
             }
 
-            var tagMappingResult = new TagHelperBinding(applicableDescriptorMappings);
+            var tagMappingResult = new TagHelperBinding(
+                tagName,
+                attributes,
+                parentTagName,
+                applicableDescriptorMappings,
+                _tagHelperPrefix);
 
             return tagMappingResult;
         }

src/Microsoft.AspNetCore.Razor.Language/TagHelperBinding.cs

@@ -0,0 +1,43 @@
+// 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.Collections.Generic;
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    public sealed class TagHelperBinding
+    {
+        private IReadOnlyDictionary<TagHelperDescriptor, IEnumerable<TagMatchingRule>> _mappings;
+
+        internal TagHelperBinding(
+            string tagName,
+            IEnumerable<KeyValuePair<string, string>> attributes,
+            string parentTagName,
+            IReadOnlyDictionary<TagHelperDescriptor, IEnumerable<TagMatchingRule>> mappings,
+            string tagHelperPrefix)
+        {
+            TagName = tagName;
+            Attributes = attributes;
+            ParentTagName = parentTagName;
+            TagHelperPrefix = tagHelperPrefix;
+
+            _mappings = mappings;
+            Descriptors = _mappings.Keys;
+        }
+
+        public IEnumerable<TagHelperDescriptor> Descriptors { get; }
+
+        public string TagName { get; }
+
+        public string ParentTagName { get; }
+
+        public IEnumerable<KeyValuePair<string, string>> Attributes { get; }
+
+        public string TagHelperPrefix { get; }
+
+        public IEnumerable<TagMatchingRule> GetBoundRules(TagHelperDescriptor descriptor)
+        {
+            return _mappings[descriptor];
+        }
+    }
+}

test/Microsoft.AspNetCore.Razor.Language.Test/TagHelperBinderTest.cs

@@ -10,6 +10,35 @@ namespace Microsoft.AspNetCore.Razor.Language
 {
     public class TagHelperBinderTest
     {
+        [Fact]
+        public void GetBinding_ReturnsBindingWithInformation()
+        {
+            // Arrange
+            var divTagHelper = TagHelperDescriptorBuilder.Create("DivTagHelper", "SomeAssembly")
+                .TagMatchingRule(rule => rule.RequireTagName("div"))
+                .Build();
+            var expectedDescriptors = new[] { divTagHelper };
+            var expectedAttributes = new[]
+            {
+                new KeyValuePair<string, string>("class", "something")
+            };
+            var tagHelperBinder = new TagHelperBinder("th:", expectedDescriptors);
+
+            // Act
+            var bindingResult = tagHelperBinder.GetBinding(
+                tagName: "th:div",
+                attributes: expectedAttributes,
+                parentTagName: "body");
+
+            // Assert
+            Assert.Equal(expectedDescriptors, bindingResult.Descriptors, TagHelperDescriptorComparer.CaseSensitive);
+            Assert.Equal("th:div", bindingResult.TagName);
+            Assert.Equal("body", bindingResult.ParentTagName);
+            Assert.Equal(expectedAttributes, bindingResult.Attributes);
+            Assert.Equal("th:", bindingResult.TagHelperPrefix);
+            Assert.Equal(divTagHelper.TagMatchingRules, bindingResult.GetBoundRules(divTagHelper), TagMatchingRuleComparer.CaseSensitive);
+        }
+
         public static TheoryData RequiredParentData
         {
             get
@@ -107,7 +136,7 @@ public static TheoryData RequiredAttributeData
                     .TagMatchingRule(rule =>
                         rule
                         .RequireTagName("input")
-                        .RequireAttribute(attribute => 
+                        .RequireAttribute(attribute =>
                             attribute
                             .Name("nodashprefix")
                             .NameComparisonMode(RequiredAttributeDescriptor.NameComparisonMode.PrefixMatch)))
@@ -129,7 +158,7 @@ public static TheoryData RequiredAttributeData
                     .TagMatchingRule(rule =>
                         rule
                         .RequireTagName(TagHelperMatchingConventions.ElementCatchAllName)
-                        .RequireAttribute(attribute => 
+                        .RequireAttribute(attribute =>
                             attribute
                             .Name("prefix-")
                             .NameComparisonMode(RequiredAttributeDescriptor.NameComparisonMode.PrefixMatch)))
@@ -406,7 +435,7 @@ public void GetDescriptors_DuplicateDescriptorsAreNotPartOfTagHelperDescriptorPo
             // Arrange
             var divDescriptor = TagHelperDescriptorBuilder.Create("foo1", "SomeAssembly")
                 .TagMatchingRule(rule => rule.RequireTagName("div"))
-                .Build(); 
+                .Build();
             var descriptors = new TagHelperDescriptor[] { divDescriptor, divDescriptor };
             var tagHelperBinder = new TagHelperBinder(null, descriptors);