Add TagHelper directive and match info to CodeDocument

src/Microsoft.AspNetCore.Razor.Evolution/RazorCodeDocumentExtensions.cs

@@ -11,6 +11,26 @@ namespace Microsoft.AspNetCore.Razor.Evolution
     {
         private static object TagHelperPrefixKey = new object();
 
+        public static TagHelperDocumentContext GetTagHelperContext(this RazorCodeDocument document)
+        {
+            if (document == null)
+            {
+                throw new ArgumentNullException(nameof(document));
+            }
+
+            return (TagHelperDocumentContext)document.Items[typeof(TagHelperDocumentContext)];
+        }
+
+        public static void SetTagHelperContext(this RazorCodeDocument document, TagHelperDocumentContext context)
+        {
+            if (document == null)
+            {
+                throw new ArgumentNullException(nameof(document));
+            }
+
+            document.Items[typeof(TagHelperDocumentContext)] = context;
+        }
+
         public static string GetTagHelperPrefix(this RazorCodeDocument document)
         {
             if (document == null)

src/Microsoft.AspNetCore.Razor.Evolution/TagHelperBinderSyntaxTreePass.cs

@@ -55,6 +55,9 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             var tagHelperPrefix = ProcessTagHelperPrefix(directives, codeDocument, errorSink);
             var root = syntaxTree.Root;
 
+            var context = TagHelperDocumentContext.Create(tagHelperPrefix, descriptors);
+            codeDocument.SetTagHelperContext(context);
+
             if (descriptors.Count == 0)
             {
                 if (errorSink.Errors.Count == 0 && errorList.Count == 0)

src/Microsoft.AspNetCore.Razor.Evolution/TagHelperDocumentContext.cs

@@ -0,0 +1,46 @@
+// 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 System.Linq;
+
+namespace Microsoft.AspNetCore.Razor.Evolution
+{
+    /// <summary>
+    /// The binding information for Tag Helpers resulted to a <see cref="RazorCodeDocument"/>. Represents the
+    /// Tag Helper information after processing by directives.
+    /// </summary>
+    public abstract class TagHelperDocumentContext
+    {
+        public static TagHelperDocumentContext Create(string prefix, IEnumerable<TagHelperDescriptor> tagHelpers)
+        {
+            if (tagHelpers == null)
+            {
+                throw new ArgumentNullException(nameof(tagHelpers));
+            }
+
+            return new DefaultTagHelperDocumentContext(prefix, tagHelpers.ToArray());
+        }
+
+        public abstract string Prefix { get; }
+
+        public abstract IReadOnlyList<TagHelperDescriptor> TagHelpers { get; }
+
+        private class DefaultTagHelperDocumentContext : TagHelperDocumentContext
+        {
+            private readonly string _prefix;
+            private readonly TagHelperDescriptor[] _tagHelpers;
+
+            public DefaultTagHelperDocumentContext(string prefix, TagHelperDescriptor[] tagHelpers)
+            {
+                _prefix = prefix;
+                _tagHelpers = tagHelpers;
+            }
+
+            public override string Prefix => _prefix;
+
+            public override IReadOnlyList<TagHelperDescriptor> TagHelpers => _tagHelpers;
+        }
+    }
+}

test/Microsoft.AspNetCore.Razor.Evolution.Test/RazorCodeDocumentExtensionsTest.cs

@@ -116,5 +116,36 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Assert
             Assert.Same(expected, codeDocument.Items[typeof(RazorCSharpDocument)]);
         }
+
+        [Fact]
+        public void GetTagHelperContext_ReturnsTagHelperContext()
+        {
+            // Arrange
+            var codeDocument = TestRazorCodeDocument.CreateEmpty();
+
+            var expected = TagHelperDocumentContext.Create(null, new TagHelperDescriptor[0]);
+            codeDocument.Items[typeof(TagHelperDocumentContext)] = expected;
+
+            // Act
+            var actual = codeDocument.GetTagHelperContext();
+
+            // Assert
+            Assert.Same(expected, actual);
+        }
+
+        [Fact]
+        public void SetTagHelperContext_SetsTagHelperContext()
+        {
+            // Arrange
+            var codeDocument = TestRazorCodeDocument.CreateEmpty();
+
+            var expected = TagHelperDocumentContext.Create(null, new TagHelperDescriptor[0]);
+
+            // Act
+            codeDocument.SetTagHelperContext(expected);
+
+            // Assert
+            Assert.Same(expected, codeDocument.Items[typeof(TagHelperDocumentContext)]);
+        }
     }
 }

test/Microsoft.AspNetCore.Razor.Evolution.Test/TagHelperBinderSyntaxTreePassTest.cs

@@ -228,6 +228,34 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             Assert.Same(originalTree, outputTree);
         }
 
+        [Fact]
+        public void Execute_SetsTagHelperDocumentContext()
+        {
+            // Arrange
+            var engine = RazorEngine.Create(builder =>
+            {
+                builder.Features.Add(new TestTagHelperFeature());
+            });
+
+            var pass = new TagHelperBinderSyntaxTreePass()
+            {
+                Engine = engine,
+            };
+
+            // No taghelper directives here so nothing is resolved.
+            var sourceDocument = TestRazorSourceDocument.Create("Hello, world");
+            var codeDocument = RazorCodeDocument.Create(sourceDocument);
+            var originalTree = RazorSyntaxTree.Parse(sourceDocument);
+
+            // Act
+            var outputTree = pass.Execute(codeDocument, originalTree);
+
+            // Assert
+            var context = codeDocument.GetTagHelperContext();
+            Assert.Null(context.Prefix);
+            Assert.Empty(context.TagHelpers);
+        }
+
         [Fact]
         public void Execute_AddsErrorWhenNoTagHelpersAreFoundInAssembly()
         {