Quick fixes from MVC

We're close to hooking up new Razor to MVC. This is a set of enabling
'quick fix' changes to resolve some blockers to using Razor.Evolution in
the product.

Main issues:
 - Types not public enough - anything in the .Legacy namespace is still
   slated from 'improvement'
 - Wrong references. We don't want .Workspaces in MVC, so moving the heavy
   lifting of TagHelper discovery to CodeAnalysis.Razor.

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

@@ -90,7 +90,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 _namespace.AddAfter<UsingStatementIRNode>(node);
             }
 
-            internal override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+            public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
             {
                 _class.Insert(0, node);
             }

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

@@ -92,7 +92,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 VisitDefault(node);
             }
 
-            internal override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+            public override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
             {
                 // As a special case the TagHelperIRNode (which must be the parent) is the one that carries
                 // the location. The execute node won't have one, but the instrumentation goes around the call

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

@@ -201,7 +201,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 Context.Writer.WriteEndMethodInvocation(endLine: false);
             }
 
-            internal override void VisitTagHelper(TagHelperIRNode node)
+            public override void VisitTagHelper(TagHelperIRNode node)
             {
                 var initialTagHelperRenderingContext = Context.TagHelperRenderingContext;
                 Context.TagHelperRenderingContext = new TagHelperRenderingContext();
@@ -209,12 +209,12 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 Context.TagHelperRenderingContext = initialTagHelperRenderingContext;
             }
 
-            internal override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+            public override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
             {
                 VisitDefault(node);
             }
 
-            internal override void VisitCreateTagHelper(CreateTagHelperIRNode node)
+            public override void VisitCreateTagHelper(CreateTagHelperIRNode node)
             {
                 var tagHelperVariableName = GetTagHelperVariableName(node.TagHelperTypeName);
 
@@ -226,7 +226,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     .WriteEndMethodInvocation();
             }
 
-            internal override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+            public override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
             {
                 var tagHelperVariableName = GetTagHelperVariableName(node.TagHelperTypeName);
                 var tagHelperRenderingContext = Context.TagHelperRenderingContext;
@@ -312,7 +312,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 }
             }
 
-            internal override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+            public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
             {
                 foreach (var tagHelperTypeName in node.UsedTagHelperTypeNames)
                 {

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

@@ -269,7 +269,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 Context.Writer.WriteEndMethodInvocation(endLine: false);
             }
 
-            internal override void VisitTagHelper(TagHelperIRNode node)
+            public override void VisitTagHelper(TagHelperIRNode node)
             {
                 var initialTagHelperRenderingContext = Context.TagHelperRenderingContext;
                 Context.TagHelperRenderingContext = new TagHelperRenderingContext();
@@ -277,7 +277,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 Context.TagHelperRenderingContext = initialTagHelperRenderingContext;
             }
 
-            internal override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+            public override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
             {
                 // Call into the tag helper scope manager to start a new tag helper scope.
                 // Also capture the value as the current execution context.
@@ -311,7 +311,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 Context.Writer.WriteEndMethodInvocation();
             }
 
-            internal override void VisitCreateTagHelper(CreateTagHelperIRNode node)
+            public override void VisitCreateTagHelper(CreateTagHelperIRNode node)
             {
                 var tagHelperVariableName = GetTagHelperVariableName(node.TagHelperTypeName);
 
@@ -328,7 +328,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     tagHelperVariableName);
             }
 
-            internal override void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
+            public override void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
             {
                 Context.Writer
                     .WriteStartInstanceMethodInvocation(
@@ -338,7 +338,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     .WriteEndMethodInvocation();
             }
 
-            internal override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+            public override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
             {
                 var attributeValueStyleParameter = $"global::{typeof(HtmlAttributeValueStyle).FullName}.{node.ValueStyle}";
                 var isConditionalAttributeValue = node.Children.Any(child => child is CSharpAttributeValueIRNode);
@@ -409,7 +409,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 }
             }
 
-            internal override void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
+            public override void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
             {
                 var tagHelperVariableName = GetTagHelperVariableName(node.TagHelperTypeName);
                 var propertyValueAccessor = GetTagHelperPropertyAccessor(tagHelperVariableName, node.AttributeName, node.Descriptor);
@@ -426,7 +426,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     .WriteEndMethodInvocation();
             }
 
-            internal override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+            public override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
             {
                 var tagHelperVariableName = GetTagHelperVariableName(node.TagHelperTypeName);
                 var tagHelperRenderingContext = Context.TagHelperRenderingContext;
@@ -528,7 +528,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     .WriteEndMethodInvocation();
             }
 
-            internal override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+            public override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
             {
                 Context.Writer
                     .Write("await ")
@@ -568,7 +568,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                         "End" /* ORIGINAL: ScopeManagerEndMethodName */);
             }
 
-            internal override void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
+            public override void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
             {
                 Context.Writer
                     .Write("private static readonly global::")
@@ -596,7 +596,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 }
             }
 
-            internal override void VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
+            public override void VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
             {
                 Context.Writer
                     .Write("private static readonly global::")
@@ -613,7 +613,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     .WriteEndMethodInvocation();
             }
 
-            internal override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+            public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
             {
                 Context.Writer.WriteLineHiddenDirective();
 

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

@@ -0,0 +1,12 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution
+{
+    public interface ITagHelperFeature : IRazorEngineFeature
+    {
+        ITagHelperDescriptorResolver Resolver { get; }
+    }
+}

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/AddPreallocatedTagHelperHtmlAttributeIRNode.cs

@@ -6,7 +6,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class AddPreallocatedTagHelperHtmlAttributeIRNode : RazorIRNode
+    public class AddPreallocatedTagHelperHtmlAttributeIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = EmptyArray;
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/AddTagHelperHtmlAttributeIRNode.cs

@@ -7,7 +7,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class AddTagHelperHtmlAttributeIRNode : RazorIRNode
+    public class AddTagHelperHtmlAttributeIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/CreateTagHelperIRNode.cs

@@ -7,7 +7,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class CreateTagHelperIRNode : RazorIRNode
+    public class CreateTagHelperIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = EmptyArray;
 
@@ -17,7 +17,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 
         public string TagHelperTypeName { get; set; }
 
-        internal TagHelperDescriptor Descriptor { get; set; }
+        public TagHelperDescriptor Descriptor { get; set; }
 
         public override void Accept(RazorIRNodeVisitor visitor)
         {

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/DeclarePreallocatedTagHelperAttributeIRNode.cs

@@ -6,7 +6,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class DeclarePreallocatedTagHelperAttributeIRNode : RazorIRNode
+    public class DeclarePreallocatedTagHelperAttributeIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = EmptyArray;
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/DeclarePreallocatedTagHelperHtmlAttributeIRNode.cs

@@ -6,7 +6,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class DeclarePreallocatedTagHelperHtmlAttributeIRNode : RazorIRNode
+    public class DeclarePreallocatedTagHelperHtmlAttributeIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = EmptyArray;
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/DeclareTagHelperFieldsIRNode.cs

@@ -3,11 +3,10 @@
 
 using System;
 using System.Collections.Generic;
-using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class DeclareTagHelperFieldsIRNode : RazorIRNode
+    public class DeclareTagHelperFieldsIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = EmptyArray;
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/ExecuteTagHelpersIRNode.cs

@@ -6,7 +6,7 @@ using System.Collections.Generic;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class ExecuteTagHelpersIRNode : RazorIRNode
+    public class ExecuteTagHelpersIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/InitializeTagHelperStructureIRNode.cs

@@ -7,7 +7,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class InitializeTagHelperStructureIRNode : RazorIRNode
+    public class InitializeTagHelperStructureIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/RazorIRNodeVisitor.cs

@@ -94,57 +94,57 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
             VisitDefault(node);
         }
 
-        internal virtual void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+        public virtual void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitTagHelper(TagHelperIRNode node)
+        public virtual void VisitTagHelper(TagHelperIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+        public virtual void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitCreateTagHelper(CreateTagHelperIRNode node)
+        public virtual void VisitCreateTagHelper(CreateTagHelperIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+        public virtual void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+        public virtual void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+        public virtual void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
+        public virtual void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
+        public virtual void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
+        public virtual void VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
         {
             VisitDefault(node);
         }
 
-        internal virtual void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
+        public virtual void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
         {
             VisitDefault(node);
         }

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/RazorIRNodeVisitorOfT.cs

@@ -95,57 +95,57 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+        public virtual TResult VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitTagHelper(TagHelperIRNode node)
+        public virtual TResult VisitTagHelper(TagHelperIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+        public virtual TResult VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitCreateTagHelper(CreateTagHelperIRNode node)
+        public virtual TResult VisitCreateTagHelper(CreateTagHelperIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+        public virtual TResult VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+        public virtual TResult VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+        public virtual TResult VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
+        public virtual TResult VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
+        public virtual TResult VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
+        public virtual TResult VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
         {
             return VisitDefault(node);
         }
 
-        internal virtual TResult VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
+        public virtual TResult VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
         {
             return VisitDefault(node);
         }

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/SetPreallocatedTagHelperPropertyIRNode.cs

@@ -2,11 +2,10 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
-using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class SetPreallocatedTagHelperPropertyIRNode : RazorIRNode
+    public class SetPreallocatedTagHelperPropertyIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = EmptyArray;
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/SetTagHelperPropertyIRNode.cs

@@ -7,7 +7,7 @@ using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class SetTagHelperPropertyIRNode : RazorIRNode
+    public class SetTagHelperPropertyIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
 

src/Microsoft.AspNetCore.Razor.Evolution/Intermediate/TagHelperIRNode.cs

@@ -3,11 +3,10 @@
 
 using System;
 using System.Collections.Generic;
-using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
-    internal class TagHelperIRNode : RazorIRNode
+    public class TagHelperIRNode : RazorIRNode
     {
         public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
 

src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ErrorSink.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
     /// <summary>
     /// Used to manage <see cref="RazorError"/>s encountered during the Razor parsing phase.
     /// </summary>
-    internal class ErrorSink
+    public class ErrorSink
     {
         private readonly List<RazorError> _errors;
 

src/Microsoft.AspNetCore.Razor.Evolution/Legacy/HtmlAttributeValueStyle.cs

@@ -3,7 +3,7 @@
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 {
-    internal enum HtmlAttributeValueStyle
+    public enum HtmlAttributeValueStyle
     {
         DoubleQuotes,
         SingleQuotes,

src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ITagHelperDescriptorResolver.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
     /// <summary>
     /// Contract used to resolve <see cref="TagHelperDescriptor"/>s.
     /// </summary>
-    internal interface ITagHelperDescriptorResolver
+    public interface ITagHelperDescriptorResolver
     {
         IEnumerable<TagHelperDescriptor> Resolve(ErrorSink errorSink);
     }

src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorError.cs

@@ -7,7 +7,7 @@ using Microsoft.Extensions.Internal;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 {
-    internal class RazorError : IEquatable<RazorError>
+    public class RazorError : IEquatable<RazorError>
     {
         internal static readonly RazorError[] EmptyArray = new RazorError[0];
 

src/Microsoft.AspNetCore.Razor.Evolution/Properties/AssemblyInfo.cs

@@ -3,6 +3,8 @@
 
 using System.Runtime.CompilerServices;
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Razor.Evolution.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Workspaces.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Workspaces, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Remote.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

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

@@ -35,7 +35,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 VisitDefault(node);
             }
 
-            internal override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+            public override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
             {
                 if (node.Children.Count != 1 || !(node.Children.First() is HtmlContentIRNode))
                 {
@@ -88,7 +88,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 node.Parent.Children[nodeIndex] = addPreAllocatedAttribute;
             }
 
-            internal override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+            public override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
             {
                 if (!node.Descriptor.IsStringProperty ||
                     node.Children.Count != 1 ||

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

@@ -21,7 +21,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
         public RazorSyntaxTree Execute(RazorCodeDocument codeDocument, RazorSyntaxTree syntaxTree)
         {
-            var resolver = Engine.Features.OfType<TagHelperFeature>().FirstOrDefault()?.Resolver;
+            var resolver = Engine.Features.OfType<ITagHelperFeature>().FirstOrDefault()?.Resolver;
             if (resolver == null)
             {
                 // No resolver, nothing to do.

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

@@ -1,19 +0,0 @@
-// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
-
-namespace Microsoft.AspNetCore.Razor.Evolution
-{
-    internal class TagHelperFeature : IRazorEngineFeature
-    {
-        public TagHelperFeature(ITagHelperDescriptorResolver resolver)
-        {
-            Resolver = resolver;
-        }
-
-        public RazorEngine Engine { get; set; }
-
-        public ITagHelperDescriptorResolver Resolver { get; }
-    }
-}

src/Microsoft.CodeAnalysis.Razor.Workspaces/DefaultTagHelperResolver.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using Microsoft.AspNetCore.Razor.Evolution;
 using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
@@ -11,18 +10,9 @@ namespace Microsoft.CodeAnalysis.Razor
 {
     internal class DefaultTagHelperResolver : TagHelperResolver
     {
-        private static readonly Version SupportedVCTHMvcVersion = new Version(1, 1);
+        public DefaultTagHelperResolver(bool designTime)
-        private readonly string ViewComponentAssembly;
-
-        public DefaultTagHelperResolver(bool designTime) : this(designTime, ViewComponentTypes.Assembly)
-        {
-        }
-
-        // Internal for testing
-        internal DefaultTagHelperResolver(bool designTime, string viewComponentAssembly)
         {
             DesignTime = designTime;
-            ViewComponentAssembly = viewComponentAssembly;
         }
 
         public bool DesignTime { get; }
@@ -40,15 +30,8 @@ namespace Microsoft.CodeAnalysis.Razor
 
         private void VisitTagHelpers(Compilation compilation, List<TagHelperDescriptor> results, ErrorSink errors)
         {
-            var @interface = compilation.GetTypeByMetadataName(TagHelperTypes.ITagHelper);
-            if (@interface == null)
-            {
-                // If ITagHelper isn't defined, then we couldn't possibly find anything.
-                return;
-            }
-
             var types = new List<INamedTypeSymbol>();
-            var visitor = new TagHelperVisitor(@interface, types);
+            var visitor = TagHelperTypeVisitor.Create(compilation, types);
 
             VisitCompilation(visitor, compilation);
 
@@ -63,20 +46,8 @@ namespace Microsoft.CodeAnalysis.Razor
 
         private void VisitViewComponents(Compilation compilation, List<TagHelperDescriptor> results, ErrorSink errors)
         {
-            var mvcViewFeaturesAssembly = compilation.References
-                .Select(reference => compilation.GetAssemblyOrModuleSymbol(reference))
-                .OfType<IAssemblySymbol>()
-                .FirstOrDefault(assembly => string.Equals(assembly.Identity.Name, ViewComponentAssembly, StringComparison.Ordinal));
-
-            if (mvcViewFeaturesAssembly == null || mvcViewFeaturesAssembly.Identity.Version < SupportedVCTHMvcVersion)
-            {
-                return;
-            }
-
-            var viewComponentAttributeSymbol = compilation.GetTypeByMetadataName(ViewComponentTypes.ViewComponentAttribute);
-            var nonViewComponentAttributeSymbol = compilation.GetTypeByMetadataName(ViewComponentTypes.NonViewComponentAttribute);
             var types = new List<INamedTypeSymbol>();
-            var visitor = new ViewComponentVisitor(viewComponentAttributeSymbol, viewComponentAttributeSymbol, types);
+            var visitor = ViewComponentTypeVisitor.Create(compilation, types);
 
             VisitCompilation(visitor, compilation);
 
@@ -109,116 +80,5 @@ namespace Microsoft.CodeAnalysis.Razor
                 }
             }
         }
-
-        // Visits top-level types and finds interface implementations.
-        internal class TagHelperVisitor : SymbolVisitor
-        {
-            private INamedTypeSymbol _interface;
-            private List<INamedTypeSymbol> _results;
-
-            public TagHelperVisitor(INamedTypeSymbol @interface, List<INamedTypeSymbol> results)
-            {
-                _interface = @interface;
-                _results = results;
-            }
-
-            public override void VisitNamedType(INamedTypeSymbol symbol)
-            {
-                if (IsTagHelper(symbol))
-                {
-                    _results.Add(symbol);
-                }
-            }
-
-            public override void VisitNamespace(INamespaceSymbol symbol)
-            {
-                foreach (var member in symbol.GetMembers())
-                {
-                    Visit(member);
-                }
-            }
-
-            internal bool IsTagHelper(INamedTypeSymbol symbol)
-            {
-                return symbol.DeclaredAccessibility == Accessibility.Public &&
-                    !symbol.IsAbstract &&
-                    !symbol.IsGenericType &&
-                    symbol.AllInterfaces.Contains(_interface);
-            }
-        }
-
-        internal class ViewComponentVisitor : SymbolVisitor
-        {
-            private INamedTypeSymbol _viewComponentAttribute;
-            private INamedTypeSymbol _nonViewComponentAttribute;
-            private List<INamedTypeSymbol> _results;
-
-            public ViewComponentVisitor(
-                INamedTypeSymbol viewComponentAttribute,
-                INamedTypeSymbol nonViewComponentAttribute,
-                List<INamedTypeSymbol> results)
-            {
-                _viewComponentAttribute = viewComponentAttribute;
-                _nonViewComponentAttribute = nonViewComponentAttribute;
-                _results = results;
-            }
-
-            public override void VisitNamedType(INamedTypeSymbol symbol)
-            {
-                if (IsViewComponent(symbol))
-                {
-                    _results.Add(symbol);
-                }
-
-                if (symbol.DeclaredAccessibility != Accessibility.Public)
-                {
-                    return;
-                }
-
-                foreach (var member in symbol.GetTypeMembers())
-                {
-                    Visit(member);
-                }
-            }
-
-            public override void VisitNamespace(INamespaceSymbol symbol)
-            {
-                foreach (var member in symbol.GetMembers())
-                {
-                    Visit(member);
-                }
-            }
-
-            internal bool IsViewComponent(INamedTypeSymbol symbol)
-            {
-                if (symbol.DeclaredAccessibility != Accessibility.Public ||
-                    symbol.IsAbstract ||
-                    symbol.IsGenericType ||
-                    AttributeIsDefined(symbol, _nonViewComponentAttribute))
-                {
-                    return false;
-                }
-
-                return symbol.Name.EndsWith(ViewComponentTypes.ViewComponentSuffix) ||
-                    AttributeIsDefined(symbol, _viewComponentAttribute);
-            }
-
-            private static bool AttributeIsDefined(INamedTypeSymbol type, INamedTypeSymbol queryAttribute)
-            {
-                if (type == null)
-                {
-                    return false;
-                }
-
-                var attribute = type.GetAttributes().Where(a => a.AttributeClass == queryAttribute).FirstOrDefault();
-
-                if (attribute != null)
-                {
-                    return true;
-                }
-
-                return AttributeIsDefined(type.BaseType, queryAttribute);
-            }
-        }
     }
 }

src/Microsoft.CodeAnalysis.Razor.Workspaces/Microsoft.CodeAnalysis.Razor.Workspaces.csproj

@@ -1,7 +1,5 @@
-<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
+<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
-
   <Import Project="..\..\build\common.props" />
-
   <PropertyGroup>
     <Description>Razor is a markup syntax for adding server-side logic to web pages. This package contains the Razor design-time infrastructure.</Description>
     <TargetFrameworks>net451;netstandard1.3</TargetFrameworks>
@@ -10,10 +8,9 @@
     <PackageTags>aspnetcore;cshtml;razor</PackageTags>
     <PackageTargetFallback>$(PackageTargetFallback);portable-net45+win8+wp8+wpa81;</PackageTargetFallback>
   </PropertyGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.Workspaces.Common" Version="1.3.0" />
     <ProjectReference Include="..\Microsoft.AspNetCore.Razor.Evolution\Microsoft.AspNetCore.Razor.Evolution.csproj" />
+    <ProjectReference Include="..\Microsoft.CodeAnalysis.Razor\Microsoft.CodeAnalysis.Razor.csproj" />
   </ItemGroup>
-
 </Project>

src/Microsoft.CodeAnalysis.Razor/DefaultMetadataReferenceFeature.cs

@@ -0,0 +1,15 @@
+// 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;
+using Microsoft.AspNetCore.Razor.Evolution;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public class DefaultMetadataReferenceFeature : IMetadataReferenceFeature
+    {
+        public RazorEngine Engine { get; set; }
+
+        public IReadOnlyList<MetadataReference> References { get; set; }
+    }
+}

src/Microsoft.CodeAnalysis.Razor/DefaultTagHelperDescriptorFactory.cs

@@ -223,14 +223,14 @@ namespace Microsoft.CodeAnalysis.Razor
             {
                 if (string.IsNullOrWhiteSpace(name))
                 {
-                    var whitespaceError = Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidRestrictChildrenAttributeNameNullWhitespace(
+                    var whitespaceError = Resources.FormatTagHelperDescriptorFactory_InvalidRestrictChildrenAttributeNameNullWhitespace(
                         TagHelperTypes.RestrictChildrenAttribute,
                         tagHelperName);
                     errorSink.OnError(SourceLocation.Zero, whitespaceError, length: 0);
                 }
                 else if (TryValidateName(
                     name,
-                    invalidCharacter => Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidRestrictChildrenAttributeName(
+                    invalidCharacter => Resources.FormatTagHelperDescriptorFactory_InvalidRestrictChildrenAttributeName(
                         TagHelperTypes.RestrictChildrenAttribute,
                         name,
                         tagHelperName,
@@ -372,15 +372,15 @@ namespace Microsoft.CodeAnalysis.Razor
             }
             else if (string.IsNullOrWhiteSpace(parentTag))
             {
-                var error = Workspaces.Resources.FormatHtmlTargetElementAttribute_NameCannotBeNullOrWhitespace(
+                var error = Resources.FormatHtmlTargetElementAttribute_NameCannotBeNullOrWhitespace(
-                    Workspaces.Resources.TagHelperDescriptorFactory_ParentTag);
+                    Resources.TagHelperDescriptorFactory_ParentTag);
                 errorSink.OnError(SourceLocation.Zero, error, length: 0);
                 return false;
             }
             else if (!TryValidateName(
                 parentTag,
-                invalidCharacter => Workspaces.Resources.FormatHtmlTargetElementAttribute_InvalidName(
+                invalidCharacter => Resources.FormatHtmlTargetElementAttribute_InvalidName(
-                    Workspaces.Resources.TagHelperDescriptorFactory_ParentTag.ToLower(),
+                    Resources.TagHelperDescriptorFactory_ParentTag.ToLower(),
                     parentTag,
                     invalidCharacter),
                 errorSink))
@@ -414,18 +414,18 @@ namespace Microsoft.CodeAnalysis.Razor
             }
 
             var targetName = targetingAttributes ?
-                Workspaces.Resources.TagHelperDescriptorFactory_Attribute :
+                Resources.TagHelperDescriptorFactory_Attribute :
-                Workspaces.Resources.TagHelperDescriptorFactory_Tag;
+                Resources.TagHelperDescriptorFactory_Tag;
 
             if (string.IsNullOrWhiteSpace(name))
             {
-                var error = Workspaces.Resources.FormatHtmlTargetElementAttribute_NameCannotBeNullOrWhitespace(targetName);
+                var error = Resources.FormatHtmlTargetElementAttribute_NameCannotBeNullOrWhitespace(targetName);
                 errorSink.OnError(SourceLocation.Zero, error, length: 0);
                 return false;
             }
             else if (!TryValidateName(
                 name,
-                invalidCharacter => Workspaces.Resources.FormatHtmlTargetElementAttribute_InvalidName(
+                invalidCharacter => Resources.FormatHtmlTargetElementAttribute_InvalidName(
                     targetName.ToLower(),
                     name,
                     invalidCharacter),
@@ -509,7 +509,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     // Specified HtmlAttributeNameAttribute.Name though property has no public setter.
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameNotNullOrEmpty(
+                        Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameNotNullOrEmpty(
                             GetFullName(type),
                             property.Name,
                             TagHelperTypes.HtmlAttributeNameAttribute,
@@ -591,13 +591,13 @@ namespace Microsoft.CodeAnalysis.Razor
             string nameOrPrefix;
             if (attributeDescriptor.IsIndexer)
             {
-                nameOrPrefix = Workspaces.Resources.TagHelperDescriptorFactory_Prefix;
+                nameOrPrefix = Resources.TagHelperDescriptorFactory_Prefix;
             }
             else if (string.IsNullOrEmpty(attributeDescriptor.Name))
             {
                 errorSink.OnError(
                     SourceLocation.Zero,
-                    Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameNullOrEmpty(
+                    Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameNullOrEmpty(
                         GetFullName(parentType),
                         attributeDescriptor.PropertyName),
                     length: 0);
@@ -606,7 +606,7 @@ namespace Microsoft.CodeAnalysis.Razor
             }
             else
             {
-                nameOrPrefix = Workspaces.Resources.TagHelperDescriptorFactory_Name;
+                nameOrPrefix = Resources.TagHelperDescriptorFactory_Name;
             }
 
             return ValidateTagHelperAttributeNameOrPrefix(
@@ -639,7 +639,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 // Provide a single error if the entire name is whitespace, not an error per character.
                 errorSink.OnError(
                     SourceLocation.Zero,
-                    Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameOrPrefixWhitespace(
+                    Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameOrPrefixWhitespace(
                         GetFullName(parentType),
                         propertyName,
                         nameOrPrefix),
@@ -654,7 +654,7 @@ namespace Microsoft.CodeAnalysis.Razor
             {
                 errorSink.OnError(
                     SourceLocation.Zero,
-                    Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameOrPrefixStart(
+                    Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameOrPrefixStart(
                         GetFullName(parentType),
                         propertyName,
                         nameOrPrefix,
@@ -672,7 +672,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 {
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameOrPrefixCharacter(
+                        Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameOrPrefixCharacter(
                             GetFullName(parentType),
                             propertyName,
                             nameOrPrefix,
@@ -749,7 +749,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     isInvalid = true;
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributePrefixNotNull(
+                        Resources.FormatTagHelperDescriptorFactory_InvalidAttributePrefixNotNull(
                             GetFullName(parentType),
                             property.Name,
                             TagHelperTypes.HtmlAttributeNameAttribute,
@@ -764,7 +764,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     isInvalid = true;
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameAttribute(
+                        Resources.FormatTagHelperDescriptorFactory_InvalidAttributeNameAttribute(
                             GetFullName(parentType),
                             property.Name,
                             TagHelperTypes.HtmlAttributeNameAttribute,
@@ -784,7 +784,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 isInvalid = true;
                 errorSink.OnError(
                     SourceLocation.Zero,
-                    Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidAttributePrefixNull(
+                    Resources.FormatTagHelperDescriptorFactory_InvalidAttributePrefixNull(
                         GetFullName(parentType),
                         property.Name,
                         TagHelperTypes.HtmlAttributeNameAttribute,
@@ -973,7 +973,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     {
                         errorSink.OnError(
                             SourceLocation.Zero,
-                            Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeCharacter(Current, _requiredAttributes),
+                            Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeCharacter(Current, _requiredAttributes),
                             length: 0);
                         return false;
                     }
@@ -1055,7 +1055,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     {
                         errorSink.OnError(
                             SourceLocation.Zero,
-                            Workspaces.Resources.FormatTagHelperDescriptorFactory_PartialRequiredAttributeOperator(_requiredAttributes, op),
+                            Resources.FormatTagHelperDescriptorFactory_PartialRequiredAttributeOperator(_requiredAttributes, op),
                             length: 0);
                         return null;
                     }
@@ -1064,7 +1064,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 {
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeOperator(Current, _requiredAttributes),
+                        Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeOperator(Current, _requiredAttributes),
                         length: 0);
                     return null;
                 }
@@ -1089,7 +1089,7 @@ namespace Microsoft.CodeAnalysis.Razor
                     {
                         errorSink.OnError(
                             SourceLocation.Zero,
-                            Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeMismatchedQuotes(_requiredAttributes, quote),
+                            Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeMismatchedQuotes(_requiredAttributes, quote),
                             length: 0);
                         return null;
                     }
@@ -1164,7 +1164,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 {
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_CouldNotFindMatchingEndBrace(_requiredAttributes),
+                        Resources.FormatTagHelperDescriptorFactory_CouldNotFindMatchingEndBrace(_requiredAttributes),
                         length: 0);
                     return null;
                 }
@@ -1172,7 +1172,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 {
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeCharacter(Current, _requiredAttributes),
+                        Resources.FormatTagHelperDescriptorFactory_InvalidRequiredAttributeCharacter(Current, _requiredAttributes),
                         length: 0);
                     return null;
                 }
@@ -1192,7 +1192,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 {
                     errorSink.OnError(
                         SourceLocation.Zero,
-                        Workspaces.Resources.FormatTagHelperDescriptorFactory_CouldNotFindMatchingEndBrace(_requiredAttributes),
+                        Resources.FormatTagHelperDescriptorFactory_CouldNotFindMatchingEndBrace(_requiredAttributes),
                         length: 0);
 
                     return false;

src/Microsoft.CodeAnalysis.Razor/DefaultTagHelperFeature.cs

@@ -0,0 +1,53 @@
+// 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;
+using System.Linq;
+using Microsoft.AspNetCore.Razor.Evolution;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
+using Microsoft.CodeAnalysis.CSharp;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public class DefaultTagHelperFeature : ITagHelperFeature
+    {
+        private RazorEngine _engine;
+        private IMetadataReferenceFeature _referenceFeature;
+
+        public RazorEngine Engine
+        {
+            get
+            {
+                return _engine;
+            }
+            set
+            {
+                _engine = value;
+                OnInitialized();
+            }
+        }
+
+        public ITagHelperDescriptorResolver Resolver { get; private set; }
+
+        private void OnInitialized()
+        {
+            _referenceFeature = Engine.Features.OfType<IMetadataReferenceFeature>().FirstOrDefault();
+            Resolver = new InnerResolver(_referenceFeature);
+        }
+
+        private class InnerResolver : ITagHelperDescriptorResolver
+        {
+            private readonly IMetadataReferenceFeature _referenceFeature;
+
+            public InnerResolver(IMetadataReferenceFeature referenceFeature)
+            {
+                _referenceFeature = referenceFeature;
+            }
+            public IEnumerable<TagHelperDescriptor> Resolve(ErrorSink errorSink)
+            {
+                var compilation = CSharpCompilation.Create("__TagHelpers", references: _referenceFeature.References);
+                return TagHelpers.GetTagHelpers(compilation);
+            }
+        }
+    }
+}

src/Microsoft.CodeAnalysis.Razor/IMetadataReferenceFeature.cs

@@ -0,0 +1,13 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution;
+using System.Collections.Generic;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public interface IMetadataReferenceFeature : IRazorEngineFeature
+    {
+        IReadOnlyList<MetadataReference> References { get; }
+    }
+}

src/Microsoft.CodeAnalysis.Razor/Microsoft.CodeAnalysis.Razor.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
+<Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <Import Project="..\..\build\common.props" />
   <PropertyGroup>
     <Description>Razor is a markup syntax for adding server-side logic to web pages. This package contains the Razor design-time infrastructure.</Description>
@@ -10,6 +10,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="1.3.0" />
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="1.3.0" />
     <ProjectReference Include="..\Microsoft.AspNetCore.Razor.Evolution\Microsoft.AspNetCore.Razor.Evolution.csproj" />
   </ItemGroup>
 </Project>

src/Microsoft.CodeAnalysis.Razor/Properties/AssemblyInfo.cs

@@ -0,0 +1,12 @@
+// 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.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Workspaces, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Workspaces.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Remote.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.VisualStudio.LanguageServices.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.VisualStudio.RazorExtension, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7")]

src/Microsoft.CodeAnalysis.Razor/Properties/Resources.Designer.cs

@@ -1,5 +1,5 @@
 // <auto-generated />
-namespace Microsoft.CodeAnalysis.Razor.Workspaces
+namespace Microsoft.CodeAnalysis.Razor
 {
     using System.Globalization;
     using System.Reflection;
@@ -8,7 +8,7 @@ namespace Microsoft.CodeAnalysis.Razor.Workspaces
     internal static class Resources
     {
         private static readonly ResourceManager _resourceManager
-            = new ResourceManager("Microsoft.CodeAnalysis.Razor.Workspaces.Resources", typeof(Resources).GetTypeInfo().Assembly);
+            = new ResourceManager("Microsoft.CodeAnalysis.Razor.Resources", typeof(Resources).GetTypeInfo().Assembly);
 
         /// <summary>
         /// {0} cannot be null or an empty string.

src/Microsoft.CodeAnalysis.Razor/Properties/ViewComponentResources.Designer.cs

@@ -1,5 +1,5 @@
 // <auto-generated />
-namespace Microsoft.CodeAnalysis.Razor.Workspaces
+namespace Microsoft.CodeAnalysis.Razor
 {
     using System.Globalization;
     using System.Reflection;
@@ -8,7 +8,7 @@ namespace Microsoft.CodeAnalysis.Razor.Workspaces
     internal static class ViewComponentResources
     {
         private static readonly ResourceManager _resourceManager
-            = new ResourceManager("Microsoft.CodeAnalysis.Razor.Workspaces.ViewComponentResources", typeof(ViewComponentResources).GetTypeInfo().Assembly);
+            = new ResourceManager("Microsoft.CodeAnalysis.Razor.ViewComponentResources", typeof(ViewComponentResources).GetTypeInfo().Assembly);
 
         /// <summary>
         /// View component '{0}' must have exactly one public method named '{1}' or '{2}'.

src/Microsoft.CodeAnalysis.Razor/TagHelperTypeVisitor.cs

@@ -0,0 +1,56 @@
+// 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.CodeAnalysis.Razor
+{
+    // Visits top-level types and finds interface implementations.
+    internal class TagHelperTypeVisitor : SymbolVisitor
+    {
+        private INamedTypeSymbol _interface;
+        private List<INamedTypeSymbol> _results;
+
+        public static TagHelperTypeVisitor Create(Compilation compilation, List<INamedTypeSymbol> results)
+        {
+            var @interface = compilation.GetTypeByMetadataName(TagHelperTypes.ITagHelper);
+            return new TagHelperTypeVisitor(@interface, results);
+        }
+
+        public TagHelperTypeVisitor(INamedTypeSymbol @interface, List<INamedTypeSymbol> results)
+        {
+            _interface = @interface;
+            _results = results;
+        }
+
+        public override void VisitNamedType(INamedTypeSymbol symbol)
+        {
+            if (IsTagHelper(symbol))
+            {
+                _results.Add(symbol);
+            }
+        }
+
+        public override void VisitNamespace(INamespaceSymbol symbol)
+        {
+            foreach (var member in symbol.GetMembers())
+            {
+                Visit(member);
+            }
+        }
+
+        internal bool IsTagHelper(INamedTypeSymbol symbol)
+        {
+            if (_interface == null)
+            {
+                return false;
+            }
+
+            return
+                symbol.DeclaredAccessibility == Accessibility.Public &&
+                !symbol.IsAbstract &&
+                !symbol.IsGenericType &&
+                symbol.AllInterfaces.Contains(_interface);
+        }
+    }
+}

src/Microsoft.CodeAnalysis.Razor/TagHelpers.cs

@@ -0,0 +1,77 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
+using System;
+using System.Collections.Generic;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public static class TagHelpers
+    {
+        public static IReadOnlyList<TagHelperDescriptor> GetTagHelpers(Compilation compilation)
+        {
+            var results = new List<TagHelperDescriptor>();
+            var errors = new ErrorSink();
+
+            VisitTagHelpers(compilation, results, errors);
+            VisitViewComponents(compilation, results, errors);
+
+            return results;
+        }
+
+        private static void VisitTagHelpers(Compilation compilation, List<TagHelperDescriptor> results, ErrorSink errors)
+        {
+            var types = new List<INamedTypeSymbol>();
+            var visitor = TagHelperTypeVisitor.Create(compilation, types);
+
+            VisitCompilation(visitor, compilation);
+
+            var factory = new DefaultTagHelperDescriptorFactory(compilation, designTime: false);
+
+            foreach (var type in types)
+            {
+                var descriptors = factory.CreateDescriptors(type, errors);
+                results.AddRange(descriptors);
+            }
+        }
+
+        private static void VisitViewComponents(Compilation compilation, List<TagHelperDescriptor> results, ErrorSink errors)
+        {
+            var types = new List<INamedTypeSymbol>();
+            var visitor = ViewComponentTypeVisitor.Create(compilation, types);
+
+            VisitCompilation(visitor, compilation);
+
+            var factory = new ViewComponentTagHelperDescriptorFactory(compilation);
+
+            foreach (var type in types)
+            {
+                try
+                {
+                    var descriptor = factory.CreateDescriptor(type);
+
+                    results.Add(descriptor);
+                }
+                catch (Exception ex)
+                {
+                    errors.OnError(SourceLocation.Zero, ex.Message, length: 0);
+                }
+            }
+        }
+
+        private static void VisitCompilation(SymbolVisitor visitor, Compilation compilation)
+        {
+            visitor.Visit(compilation.Assembly.GlobalNamespace);
+
+            foreach (var reference in compilation.References)
+            {
+                if (compilation.GetAssemblyOrModuleSymbol(reference) is IAssemblySymbol assembly)
+                {
+                    visitor.Visit(assembly.GlobalNamespace);
+                }
+            }
+        }
+    }
+}

src/Microsoft.CodeAnalysis.Razor/ViewComponentTagHelperDescriptorFactory.cs

@@ -7,7 +7,6 @@ using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Razor.Evolution;
-using Microsoft.CodeAnalysis.Razor.Workspaces;
 
 namespace Microsoft.CodeAnalysis.Razor
 {

src/Microsoft.CodeAnalysis.Razor/ViewComponentTypeVisitor.cs

@@ -0,0 +1,112 @@
+// 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.CodeAnalysis.Razor
+{
+    internal class ViewComponentTypeVisitor : SymbolVisitor
+    {
+        private static readonly Version SupportedVCTHMvcVersion = new Version(1, 1);
+
+        private INamedTypeSymbol _viewComponentAttribute;
+        private INamedTypeSymbol _nonViewComponentAttribute;
+        private List<INamedTypeSymbol> _results;
+
+        public static ViewComponentTypeVisitor Create(Compilation compilation, List<INamedTypeSymbol> results)
+        {
+            var enabled = false;
+            foreach (var reference in compilation.References)
+            {
+                var symbol = compilation.GetAssemblyOrModuleSymbol(reference) as IAssemblySymbol;
+                if (symbol != null)
+                {
+                    if (string.Equals(symbol.Identity.Name, ViewComponentTypes.Assembly, StringComparison.Ordinal) &&
+                        symbol.Identity.Version > ViewComponentTypes.AssemblyVersion)
+                    {
+                        enabled = true;
+                        break;
+                    }
+                }
+            }
+
+            var vcAttribute = enabled ? compilation.GetTypeByMetadataName(ViewComponentTypes.ViewComponentAttribute) : null;
+            var nonVCAttribute = enabled ? compilation.GetTypeByMetadataName(ViewComponentTypes.NonViewComponentAttribute) : null;
+            return new ViewComponentTypeVisitor(vcAttribute, nonVCAttribute, results);
+        }
+
+        public ViewComponentTypeVisitor(
+            INamedTypeSymbol viewComponentAttribute,
+            INamedTypeSymbol nonViewComponentAttribute,
+            List<INamedTypeSymbol> results)
+        {
+            _viewComponentAttribute = viewComponentAttribute;
+            _nonViewComponentAttribute = nonViewComponentAttribute;
+            _results = results;
+        }
+
+        public override void VisitNamedType(INamedTypeSymbol symbol)
+        {
+            if (IsViewComponent(symbol))
+            {
+                _results.Add(symbol);
+            }
+
+            if (symbol.DeclaredAccessibility != Accessibility.Public)
+            {
+                return;
+            }
+
+            foreach (var member in symbol.GetTypeMembers())
+            {
+                Visit(member);
+            }
+        }
+
+        public override void VisitNamespace(INamespaceSymbol symbol)
+        {
+            foreach (var member in symbol.GetMembers())
+            {
+                Visit(member);
+            }
+        }
+
+        internal bool IsViewComponent(INamedTypeSymbol symbol)
+        {
+            if (_viewComponentAttribute == null)
+            {
+                return false;
+            }
+
+            if (symbol.DeclaredAccessibility != Accessibility.Public ||
+                symbol.IsAbstract ||
+                symbol.IsGenericType ||
+                AttributeIsDefined(symbol, _nonViewComponentAttribute))
+            {
+                return false;
+            }
+
+            return symbol.Name.EndsWith(ViewComponentTypes.ViewComponentSuffix) ||
+                AttributeIsDefined(symbol, _viewComponentAttribute);
+        }
+
+        private static bool AttributeIsDefined(INamedTypeSymbol type, INamedTypeSymbol queryAttribute)
+        {
+            if (type == null)
+            {
+                return false;
+            }
+
+            var attribute = type.GetAttributes().Where(a => a.AttributeClass == queryAttribute).FirstOrDefault();
+
+            if (attribute != null)
+            {
+                return true;
+            }
+
+            return AttributeIsDefined(type.BaseType, queryAttribute);
+        }
+    }
+}

src/Microsoft.CodeAnalysis.Razor/ViewComponentTypes.cs

@@ -1,12 +1,16 @@
 // 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;
+
 namespace Microsoft.CodeAnalysis.Razor
 {
     internal static class ViewComponentTypes
     {
         public const string Assembly = "Microsoft.AspNetCore.Mvc.ViewFeatures";
 
+        public static readonly Version AssemblyVersion = new Version(1, 1, 0, 0);
+
         public const string ViewComponentSuffix = "ViewComponent";
 
         public const string ViewComponentAttribute = "Microsoft.AspNetCore.Mvc.ViewComponentAttribute";

src/Microsoft.CodeAnalysis.Razor/XmlMemberDocumentation.cs

@@ -5,7 +5,6 @@ using System;
 using System.Diagnostics;
 using System.Text;
 using System.Xml.Linq;
-using Microsoft.CodeAnalysis.Razor.Workspaces;
 
 namespace Microsoft.CodeAnalysis.Razor
 {

test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/CodeGenerationIntegrationTest.cs

@@ -1421,7 +1421,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
                 builder =>
                 {
                     builder.Features.Add(new ApiSetsIRTestAdapter());
-                    builder.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(descriptors)));
+                    builder.AddTagHelpers(descriptors);
                 });
             var document = CreateCodeDocument();
 
@@ -1439,7 +1439,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
                 builder =>
                 {
                     builder.Features.Add(new ApiSetsIRTestAdapter());
-                    builder.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(descriptors)));
+                    builder.AddTagHelpers(descriptors);
                 });
             var document = CreateCodeDocument();
 

test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/RazorIRNodeWriter.cs

@@ -87,47 +87,47 @@ namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
             WriteContentNode(node, node.Content);
         }
 
-        internal override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+        public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
         {
             WriteContentNode(node, node.UsedTagHelperTypeNames.ToArray());
         }
 
-        internal override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+        public override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
         {
             WriteContentNode(node, node.TagName, string.Format("{0}.{1}", nameof(TagMode), node.TagMode));
         }
 
-        internal override void VisitCreateTagHelper(CreateTagHelperIRNode node)
+        public override void VisitCreateTagHelper(CreateTagHelperIRNode node)
         {
             WriteContentNode(node, node.TagHelperTypeName);
         }
 
-        internal override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+        public override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
         {
             WriteContentNode(node, node.AttributeName, node.PropertyName, string.Format("HtmlAttributeValueStyle.{0}", node.ValueStyle));
         }
 
-        internal override void VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
+        public override void VisitDeclarePreallocatedTagHelperAttribute(DeclarePreallocatedTagHelperAttributeIRNode node)
         {
             WriteContentNode(node, node.VariableName, node.Name, node.Value, string.Format("HtmlAttributeValueStyle.{0}", node.ValueStyle));
         }
 
-        internal override void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
+        public override void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
         {
             WriteContentNode(node, node.VariableName, node.AttributeName, node.PropertyName);
         }
 
-        internal override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+        public override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
         {
             WriteContentNode(node, node.Name, string.Format("{0}.{1}", nameof(HtmlAttributeValueStyle), node.ValueStyle));
         }
 
-        internal override void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
+        public override void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
         {
             WriteContentNode(node, node.VariableName, node.Name, node.Value, string.Format("{0}.{1}", nameof(HtmlAttributeValueStyle), node.ValueStyle));
         }
 
-        internal override void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
+        public override void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedTagHelperHtmlAttributeIRNode node)
         {
             WriteContentNode(node, node.VariableName);
         }

test/Microsoft.AspNetCore.Razor.Evolution.Test/Intermediate/DefaultRazorIRLoweringPhaseIntegrationTest.cs

@@ -337,7 +337,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
             {
                 builder?.Invoke(b);
 
-                b.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(tagHelpers)));
+                b.AddTagHelpers(tagHelpers);
             });
 
             for (var i = 0; i < engine.Phases.Count; i++)

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

@@ -1,6 +1,7 @@
 // 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;
 using System.Linq;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
@@ -9,14 +10,19 @@ namespace Microsoft.AspNetCore.Razor.Evolution
     {
         public static IRazorEngineBuilder AddTagHelpers(this IRazorEngineBuilder builder, params TagHelperDescriptor[] tagHelpers)
         {
-            var resolver = (TestTagHelperDescriptorResolver)builder.Features.OfType<TagHelperFeature>().FirstOrDefault()?.Resolver;
+            return AddTagHelpers(builder, (IEnumerable<TagHelperDescriptor>)tagHelpers);
-            if (resolver == null)
+        }
+
+        public static IRazorEngineBuilder AddTagHelpers(this IRazorEngineBuilder builder, IEnumerable<TagHelperDescriptor> tagHelpers)
+        {
+            var feature = (TestTagHelperFeature)builder.Features.OfType<ITagHelperFeature>().FirstOrDefault();
+            if (feature == null)
             {
-                resolver = new TestTagHelperDescriptorResolver();
+                feature = new TestTagHelperFeature();
-                builder.Features.Add(new TagHelperFeature(resolver));
+                builder.Features.Add(feature);
             }
 
-            resolver.TagHelpers.AddRange(tagHelpers);
+            feature.TagHelpers.AddRange(tagHelpers);
             return builder;
         }
     }

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

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 using Xunit;
 using System.Linq;
+using Moq;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
 {
@@ -81,9 +82,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Arrange
             var engine = RazorEngine.Create(builder =>
             {
-
+                builder.Features.Add(Mock.Of<ITagHelperFeature>());
-                var tagHelperFeature = new TagHelperFeature(resolver: null);
-                builder.Features.Add(tagHelperFeature);
             });
             var pass = new TagHelperBinderSyntaxTreePass()
             {
@@ -107,9 +106,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Arrange
             var engine = RazorEngine.Create(builder =>
             {
-                var resolver = new TestTagHelperDescriptorResolver();
+                builder.Features.Add(new TestTagHelperFeature());
-                var tagHelperFeature = new TagHelperFeature(resolver);
-                builder.Features.Add(tagHelperFeature);
             });
 
             var pass = new TagHelperBinderSyntaxTreePass()
@@ -136,9 +133,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Arrange
             var engine = RazorEngine.Create(builder =>
             {
-                var resolver = new TestTagHelperDescriptorResolver();
+                builder.Features.Add(new TestTagHelperFeature());
-                var tagHelperFeature = new TagHelperFeature(resolver);
-                builder.Features.Add(tagHelperFeature);
             });
 
             var pass = new TagHelperBinderSyntaxTreePass()
@@ -173,8 +168,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             var engine = RazorEngine.Create(builder =>
             {
                 var resolver = new ErrorLoggingTagHelperDescriptorResolver(resolverError);
-                var tagHelperFeature = new TagHelperFeature(resolver);
+                builder.Features.Add(Mock.Of<ITagHelperFeature>(f => f.Resolver == resolver));
-                builder.Features.Add(tagHelperFeature);
             });
 
             var pass = new TagHelperBinderSyntaxTreePass()

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

@@ -0,0 +1,27 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+using System.Collections.Generic;
+
+namespace Microsoft.AspNetCore.Razor.Evolution
+{
+    public class TestTagHelperFeature : ITagHelperFeature
+    {
+        public TestTagHelperFeature()
+        {
+            Resolver = new TestTagHelperDescriptorResolver();
+        }
+
+        public TestTagHelperFeature(IEnumerable<TagHelperDescriptor> tagHelpers)
+        {
+            Resolver = new TestTagHelperDescriptorResolver(tagHelpers);
+        }
+
+        public RazorEngine Engine { get; set; }
+
+        public List<TagHelperDescriptor> TagHelpers => ((TestTagHelperDescriptorResolver)Resolver).TagHelpers;
+
+        public ITagHelperDescriptorResolver Resolver { get; }
+    }
+}

test/Microsoft.CodeAnalysis.Razor.Test/TagHelperTypeVisitorTest.cs

@@ -0,0 +1,121 @@
+// 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;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+using Microsoft.CodeAnalysis.Razor.Workspaces.Test;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Razor.Workspaces
+{
+    public class TagHelperTypeVisitorTest
+    {
+        private static Compilation Compilation { get; } = TestCompilation.Create();
+
+        private static INamedTypeSymbol ITagHelperSymbol { get; } = Compilation.GetTypeByMetadataName(TagHelperTypes.ITagHelper);
+
+        [Fact]
+        public void IsTagHelper_PlainTagHelper_ReturnsTrue()
+        {
+            // Arrange
+            var testVisitor = new TagHelperTypeVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_PlainTagHelper).FullName);
+
+            // Act
+            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
+
+            // Assert
+            Assert.True(isTagHelper);
+        }
+
+        [Fact]
+        public void IsTagHelper_InheritedTagHelper_ReturnsTrue()
+        {
+            // Arrange
+            var testVisitor = new TagHelperTypeVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_InheritedTagHelper).FullName);
+
+            // Act
+            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
+
+            // Assert
+            Assert.True(isTagHelper);
+        }
+
+        [Fact]
+        public void IsTagHelper_AbstractTagHelper_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new TagHelperTypeVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_AbstractTagHelper).FullName);
+
+            // Act
+            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isTagHelper);
+        }
+
+        [Fact]
+        public void IsTagHelper_GenericTagHelper_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new TagHelperTypeVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_GenericTagHelper<>).FullName);
+
+            // Act
+            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isTagHelper);
+        }
+
+        [Fact]
+        public void IsTagHelper_InternalTagHelper_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new TagHelperTypeVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_InternalTagHelper).FullName);
+
+            // Act
+            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isTagHelper);
+        }
+
+
+
+
+        public class Invalid_NestedPublicTagHelper : TagHelper
+        {
+        }
+
+        public class Valid_NestedPublicViewComponent
+        {
+            public string Invoke(string foo) => null;
+        }
+    }
+
+    public abstract class Invalid_AbstractTagHelper : TagHelper
+    {
+    }
+
+    public class Invalid_GenericTagHelper<T> : TagHelper
+    {
+    }
+
+    internal class Invalid_InternalTagHelper : TagHelper
+    {
+    }
+
+    public class Valid_PlainTagHelper : TagHelper
+    {
+    }
+
+    public class Valid_InheritedTagHelper : Valid_PlainTagHelper
+    {
+    }
+}

test/Microsoft.CodeAnalysis.Razor.Test/TestCompilation.cs

@@ -6,7 +6,7 @@ using System.Collections.Generic;
 using System.Linq;
 using Microsoft.CodeAnalysis.CSharp;
 
-namespace Microsoft.CodeAnalysis.Razor.Workspaces.Test
+namespace Microsoft.CodeAnalysis.Razor
 {
     public static class TestCompilation
     {

test/Microsoft.CodeAnalysis.Razor.Test/ViewComponentTypeVisitorTest.cs

@@ -0,0 +1,198 @@
+// 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 Xunit;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public class ViewComponentTypeVisitorTest
+    {
+        private static Compilation Compilation { get; } = TestCompilation.Create();
+
+        // In practice MVC will provide a marker attribute for ViewComponents. To prevent a circular reference between MVC and Razor
+        // we can use a test class as a marker.
+        private static INamedTypeSymbol TestViewComponentAttributeSymbol { get; } = Compilation.GetTypeByMetadataName(typeof(TestViewComponentAttribute).FullName);
+        private static INamedTypeSymbol TestNonViewComponentAttributeSymbol { get; } = Compilation.GetTypeByMetadataName(typeof(TestNonViewComponentAttribute).FullName);
+
+        [Fact]
+        public void IsViewComponent_PlainViewComponent_ReturnsTrue()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_PlainViewComponent).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.True(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_DecoratedViewComponent_ReturnsTrue()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_DecoratedVC).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.True(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_InheritedViewComponent_ReturnsTrue()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_InheritedVC).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.True(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_AbstractViewComponent_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_AbstractViewComponent).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_GenericViewComponent_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_GenericViewComponent<>).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_InternalViewComponent_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_InternalViewComponent).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_DecoratedNonViewComponent_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_DecoratedViewComponent).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isViewComponent);
+        }
+
+        [Fact]
+        public void IsViewComponent_InheritedNonViewComponent_ReturnsFalse()
+        {
+            // Arrange
+            var testVisitor = new ViewComponentTypeVisitor(
+                TestViewComponentAttributeSymbol,
+                TestNonViewComponentAttributeSymbol,
+                new List<INamedTypeSymbol>());
+            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_InheritedViewComponent).FullName);
+
+            // Act
+            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
+
+            // Assert
+            Assert.False(isViewComponent);
+        }
+
+        public abstract class Invalid_AbstractViewComponent
+        {
+        }
+
+        public class Invalid_GenericViewComponent<T>
+        {
+        }
+
+        internal class Invalid_InternalViewComponent
+        {
+        }
+
+        public class Valid_PlainViewComponent
+        {
+        }
+
+        [TestViewComponent]
+        public class Valid_DecoratedVC
+        {
+        }
+
+        public class Valid_InheritedVC : Valid_DecoratedVC
+        {
+        }
+
+        [TestNonViewComponent]
+        public class Invalid_DecoratedViewComponent
+        {
+        }
+
+        [TestViewComponent]
+        public class Invalid_InheritedViewComponent : Invalid_DecoratedViewComponent
+        {
+        }
+
+        public class TestViewComponentAttribute : Attribute
+        {
+        }
+
+        public class TestNonViewComponentAttribute : Attribute
+        {
+        }
+    }
+}

test/Microsoft.CodeAnalysis.Razor.Workspaces.Test/DefaultTagHelperResolverTest.cs

@@ -1,334 +0,0 @@
-// 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;
-using Microsoft.AspNetCore.Razor.TagHelpers;
-using Microsoft.CodeAnalysis.Razor.Workspaces.Test;
-using Xunit;
-
-namespace Microsoft.CodeAnalysis.Razor.Workspaces
-{
-    public class DefaultTagHelperResolverTest
-    {
-        private static Compilation Compilation { get; } = TestCompilation.Create();
-
-        private static INamedTypeSymbol ITagHelperSymbol { get; } = Compilation.GetTypeByMetadataName(TagHelperTypes.ITagHelper);
-
-        // In practice MVC will provide a marker attribute for ViewComponents. To prevent a circular reference between MVC and Razor
-        // we can use a test class as a marker.
-        private static INamedTypeSymbol TestViewComponentAttributeSymbol { get; } = Compilation.GetTypeByMetadataName(typeof(TestViewComponentAttribute).FullName);
-        private static INamedTypeSymbol TestNonViewComponentAttributeSymbol { get; } = Compilation.GetTypeByMetadataName(typeof(TestNonViewComponentAttribute).FullName);
-
-        [Fact]
-        public void IsTagHelper_PlainTagHelper_ReturnsTrue()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.TagHelperVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_PlainTagHelper).FullName);
-
-            // Act
-            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
-
-            // Assert
-            Assert.True(isTagHelper);
-        }
-
-        [Fact]
-        public void IsTagHelper_InheritedTagHelper_ReturnsTrue()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.TagHelperVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_InheritedTagHelper).FullName);
-
-            // Act
-            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
-
-            // Assert
-            Assert.True(isTagHelper);
-        }
-
-        [Fact]
-        public void IsTagHelper_AbstractTagHelper_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.TagHelperVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_AbstractTagHelper).FullName);
-
-            // Act
-            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isTagHelper);
-        }
-
-        [Fact]
-        public void IsTagHelper_GenericTagHelper_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.TagHelperVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_GenericTagHelper<>).FullName);
-
-            // Act
-            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isTagHelper);
-        }
-
-        [Fact]
-        public void IsTagHelper_InternalTagHelper_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.TagHelperVisitor(ITagHelperSymbol, new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_InternalTagHelper).FullName);
-
-            // Act
-            var isTagHelper = testVisitor.IsTagHelper(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isTagHelper);
-        }
-
-        [Fact]
-        public void GetTagHelpers_NestedTagHelpersAreNotFound()
-        {
-            // Arrange
-            var resolver = new DefaultTagHelperResolver(designTime: false);
-            var expectedTypeName = typeof(DefaultTagHelperResolver).FullName + "." + nameof(Invalid_NestedPublicTagHelper);
-
-            // Act
-            var descriptors = resolver.GetTagHelpers(Compilation);
-
-            // Assert
-            var matchingDescriptors = descriptors
-                .Where(descriptor => string.Equals(descriptor.TypeName, expectedTypeName, StringComparison.Ordinal));
-            Assert.Empty(matchingDescriptors);
-        }
-
-        [Fact]
-        public void IsViewComponent_PlainViewComponent_ReturnsTrue()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_PlainViewComponent).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.True(isViewComponent);
-        }
-
-        [Fact]
-        public void IsViewComponent_DecoratedViewComponent_ReturnsTrue()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_DecoratedVC).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.True(isViewComponent);
-        }
-
-        [Fact]
-        public void IsViewComponent_InheritedViewComponent_ReturnsTrue()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Valid_InheritedVC).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.True(isViewComponent);
-        }
-
-        [Fact]
-        public void IsViewComponent_AbstractViewComponent_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_AbstractViewComponent).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isViewComponent);
-        }
-
-        [Fact]
-        public void IsViewComponent_GenericViewComponent_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_GenericViewComponent<>).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isViewComponent);
-        }
-
-        [Fact]
-        public void IsViewComponent_InternalViewComponent_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_InternalViewComponent).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isViewComponent);
-        }
-
-        [Fact]
-        public void GetTagHelpers_NestedViewComponentTagHelpersAreFound()
-        {
-            // Arrange
-            var resolver = new DefaultTagHelperResolver(
-                designTime: false, 
-                viewComponentAssembly: typeof(DefaultTagHelperResolverTest).Assembly.GetName().Name);
-            var expectedTypeName = "__Generated__" + nameof(Valid_NestedPublicViewComponent) + "TagHelper";
-
-            // Act
-            var descriptors = resolver.GetTagHelpers(Compilation);
-
-            // Assert
-            Assert.Single(descriptors, descriptor => string.Equals(descriptor.TypeName, expectedTypeName, StringComparison.Ordinal));
-        }
-
-        [Fact]
-        public void IsViewComponent_DecoratedNonViewComponent_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_DecoratedViewComponent).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isViewComponent);
-        }
-
-        [Fact]
-        public void IsViewComponent_InheritedNonViewComponent_ReturnsFalse()
-        {
-            // Arrange
-            var testVisitor = new DefaultTagHelperResolver.ViewComponentVisitor(
-                TestViewComponentAttributeSymbol,
-                TestNonViewComponentAttributeSymbol,
-                new List<INamedTypeSymbol>());
-            var tagHelperSymbol = Compilation.GetTypeByMetadataName(typeof(Invalid_InheritedViewComponent).FullName);
-
-            // Act
-            var isViewComponent = testVisitor.IsViewComponent(tagHelperSymbol);
-
-            // Assert
-            Assert.False(isViewComponent);
-        }
-
-        public class Invalid_NestedPublicTagHelper : TagHelper
-        {
-        }
-
-        public class Valid_NestedPublicViewComponent
-        {
-            public string Invoke(string foo) => null;
-        }
-    }
-
-    public abstract class Invalid_AbstractTagHelper : TagHelper
-    {
-    }
-
-    public class Invalid_GenericTagHelper<T> : TagHelper
-    {
-    }
-
-    internal class Invalid_InternalTagHelper : TagHelper
-    {
-    }
-
-    public class Valid_PlainTagHelper : TagHelper
-    {
-    }
-
-    public class Valid_InheritedTagHelper : Valid_PlainTagHelper
-    {
-    }
-
-    public abstract class Invalid_AbstractViewComponent
-    {
-    }
-
-    public class Invalid_GenericViewComponent<T>
-    {
-    }
-
-    internal class Invalid_InternalViewComponent
-    {
-    }
-
-    public class Valid_PlainViewComponent
-    {
-    }
-
-    [TestViewComponent]
-    public class Valid_DecoratedVC
-    {
-    }
-
-    public class Valid_InheritedVC : Valid_DecoratedVC
-    {
-    }
-
-    [TestNonViewComponent]
-    public class Invalid_DecoratedViewComponent
-    {
-    }
-
-    [TestViewComponent]
-    public class Invalid_InheritedViewComponent : Invalid_DecoratedViewComponent
-    {
-    }
-
-    public class TestViewComponentAttribute : Attribute
-    {
-    }
-
-    public class TestNonViewComponentAttribute : Attribute
-    {
-    }
-}