[Fixes #881] Added TagHelper IR support

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

@@ -159,7 +159,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                         contentLength,
                         sourceRangeStart.FilePath ?? _codeDocument.Source.Filename);
                 }
-
             }
 
             public override void VisitExpressionSpan(ExpressionChunkGenerator chunkGenerator, Span span)
@@ -253,6 +252,145 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 Builder.Pop();
             }
 
+            public override void VisitStartTagHelperBlock(TagHelperChunkGenerator chunkGenerator, Block block)
+            {
+                var tagHelperBlock = block as TagHelperBlock;
+                if (tagHelperBlock == null)
+                {
+                    return;
+                }
+
+                DeclareTagHelperFields(tagHelperBlock);
+
+                Builder.Push(new TagHelperIRNode());
+
+                Builder.Push(new InitializeTagHelperStructureIRNode()
+                {
+                    TagName = tagHelperBlock.TagName,
+                    TagMode = tagHelperBlock.TagMode
+                });
+            }
+
+            public override void VisitEndTagHelperBlock(TagHelperChunkGenerator chunkGenerator, Block block)
+            {
+                var tagHelperBlock = block as TagHelperBlock;
+                if (tagHelperBlock == null)
+                {
+                    return;
+                }
+
+                Builder.Pop(); // Pop InitializeTagHelperStructureIRNode
+
+                AddTagHelperCreation(tagHelperBlock.Descriptors);
+                AddTagHelperAttributes(tagHelperBlock.Attributes, tagHelperBlock.Descriptors);
+                AddExecuteTagHelpers();
+
+                Builder.Pop(); // Pop TagHelperIRNode
+            }
+
+            public override void VisitAddTagHelperSpan(AddTagHelperChunkGenerator chunkGenerator, Span span)
+            {
+            }
+
+            public override void VisitRemoveTagHelperSpan(RemoveTagHelperChunkGenerator chunkGenerator, Span span)
+            {
+            }
+
+            public override void VisitTagHelperPrefixDirectiveSpan(TagHelperPrefixDirectiveChunkGenerator chunkGenerator, Span span)
+            {
+            }
+
+            private void DeclareTagHelperFields(TagHelperBlock block)
+            {
+                var declareFieldsNode = Class.Children.OfType<DeclareTagHelperFieldsIRNode>().SingleOrDefault();
+                if (declareFieldsNode == null)
+                {
+                    declareFieldsNode = new DeclareTagHelperFieldsIRNode();
+                    declareFieldsNode.Parent = Class;
+
+                    var methodIndex = Class.Children.IndexOf(Method);
+                    Class.Children.Insert(methodIndex, declareFieldsNode);
+                }
+
+                foreach (var descriptor in block.Descriptors)
+                {
+                    declareFieldsNode.UsedTagHelperTypeNames.Add(descriptor.TypeName);
+                }
+            }
+
+            private void AddTagHelperCreation(IEnumerable<TagHelperDescriptor> descriptors)
+            {
+                foreach (var descriptor in descriptors)
+                {
+                    var createTagHelper = new CreateTagHelperIRNode()
+                    {
+                        TagHelperTypeName = descriptor.TypeName,
+                        Descriptor = descriptor
+                    };
+
+                    Builder.Add(createTagHelper);
+                }
+            }
+
+            private void AddTagHelperAttributes(IList<TagHelperAttributeNode> attributes, IEnumerable<TagHelperDescriptor> descriptors)
+            {
+                var renderedBoundAttributeNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+                foreach (var attribute in attributes)
+                {
+                    var attributeValueNode = attribute.Value;
+                    var associatedDescriptors = descriptors.Where(descriptor =>
+                        descriptor.Attributes.Any(attributeDescriptor => attributeDescriptor.IsNameMatch(attribute.Name)));
+
+                    if (associatedDescriptors.Any() && renderedBoundAttributeNames.Add(attribute.Name))
+                    {
+                        if (attributeValueNode == null)
+                        {
+                            // Minimized attributes are not valid for bound attributes. TagHelperBlockRewriter has already
+                            // logged an error if it was a bound attribute; so we can skip.
+                            continue;
+                        }
+
+                        foreach (var associatedDescriptor in associatedDescriptors)
+                        {
+                            var associatedAttributeDescriptor = associatedDescriptor.Attributes.First(
+                                attributeDescriptor => attributeDescriptor.IsNameMatch(attribute.Name));
+                            var setTagHelperProperty = new SetTagHelperPropertyIRNode()
+                            {
+                                PropertyName = associatedAttributeDescriptor.PropertyName,
+                                AttributeName = attribute.Name,
+                                TagHelperTypeName = associatedDescriptor.TypeName,
+                                Descriptor = associatedAttributeDescriptor,
+                                ValueStyle = attribute.ValueStyle
+                            };
+
+                            Builder.Push(setTagHelperProperty);
+                            attributeValueNode.Accept(this);
+                            Builder.Pop();
+                        }
+                    }
+                    else
+                    {
+                        var addHtmlAttribute = new AddTagHelperHtmlAttributeIRNode()
+                        {
+                            Name = attribute.Name,
+                            ValueStyle = attribute.ValueStyle
+                        };
+
+                        Builder.Push(addHtmlAttribute);
+                        if (attributeValueNode != null)
+                        {
+                            attributeValueNode.Accept(this);
+                        }
+                        Builder.Pop();
+                    }
+                }
+            }
+
+            private void AddExecuteTagHelpers()
+            {
+                Builder.Add(new ExecuteTagHelpersIRNode());
+            }
+
             private MappingLocation BuildSourceRangeFromNode(SyntaxTreeNode node)
             {
                 var location = node.Start;

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

@@ -9,7 +9,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
     {
         public RazorEngine Engine { get; set; }
 
-        public int Order => 150;
+        public int Order => 100;
 
         public RazorSyntaxTree Execute(RazorCodeDocument codeDocument, RazorSyntaxTree syntaxTree)
         {

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

@@ -0,0 +1,42 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class AddTagHelperHtmlAttributeIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public string Name { get; set; }
+
+        internal HtmlAttributeValueStyle ValueStyle { get; set; }
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitAddTagHelperHtmlAttribute(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitAddTagHelperHtmlAttribute(this);
+        }
+    }
+}

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

@@ -0,0 +1,42 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class CreateTagHelperIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = EmptyArray;
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public string TagHelperTypeName { get; set; }
+
+        internal TagHelperDescriptor Descriptor { get; set; }
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitCreateTagHelper(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitCreateTagHelper(this);
+        }
+    }
+}

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

@@ -0,0 +1,40 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class DeclareTagHelperFieldsIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = EmptyArray;
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public ISet<string> UsedTagHelperTypeNames { get; set; } = new HashSet<string>(StringComparer.Ordinal);
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitDeclareTagHelperFields(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitDeclareTagHelperFields(this);
+        }
+    }
+}

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

@@ -0,0 +1,38 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class ExecuteTagHelpersIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitExecuteTagHelpers(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitExecuteTagHelpers(this);
+        }
+    }
+}

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

@@ -0,0 +1,42 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class InitializeTagHelperStructureIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public string TagName { get; set; }
+
+        internal TagMode TagMode { get; set; }
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitInitializeTagHelperStructure(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitInitializeTagHelperStructure(this);
+        }
+    }
+}

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

@@ -93,5 +93,40 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
         {
             VisitDefault(node);
         }
+
+        internal virtual void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+        {
+            VisitDefault(node);
+        }
+
+        internal virtual void VisitTagHelper(TagHelperIRNode node)
+        {
+            VisitDefault(node);
+        }
+
+        internal virtual void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+        {
+            VisitDefault(node);
+        }
+
+        internal virtual void VisitCreateTagHelper(CreateTagHelperIRNode node)
+        {
+            VisitDefault(node);
+        }
+
+        internal virtual void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+        {
+            VisitDefault(node);
+        }
+
+        internal virtual void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+        {
+            VisitDefault(node);
+        }
+
+        internal virtual void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+        {
+            VisitDefault(node);
+        }
     }
 }

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

@@ -94,5 +94,40 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
         {
             return VisitDefault(node);
         }
+
+        internal virtual TResult VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+        {
+            return VisitDefault(node);
+        }
+
+        internal virtual TResult VisitTagHelper(TagHelperIRNode node)
+        {
+            return VisitDefault(node);
+        }
+
+        internal virtual TResult VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+        {
+            return VisitDefault(node);
+        }
+
+        internal virtual TResult VisitCreateTagHelper(CreateTagHelperIRNode node)
+        {
+            return VisitDefault(node);
+        }
+
+        internal virtual TResult VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+        {
+            return VisitDefault(node);
+        }
+
+        internal virtual TResult VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+        {
+            return VisitDefault(node);
+        }
+
+        internal virtual TResult VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+        {
+            return VisitDefault(node);
+        }
     }
 }

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

@@ -0,0 +1,48 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class SetTagHelperPropertyIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public string TagHelperTypeName { get; set; }
+
+        public string PropertyName { get; set; }
+
+        public string AttributeName { get; set; }
+
+        internal HtmlAttributeValueStyle ValueStyle { get; set; }
+
+        internal TagHelperAttributeDescriptor Descriptor { get; set; }
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitSetTagHelperProperty(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitSetTagHelperProperty(this);
+        }
+    }
+}

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

@@ -0,0 +1,38 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Legacy;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
+{
+    internal class TagHelperIRNode : RazorIRNode
+    {
+        public override IList<RazorIRNode> Children { get; } = new List<RazorIRNode>();
+
+        public override RazorIRNode Parent { get; set; }
+
+        internal override MappingLocation SourceRange { get; set; }
+
+        public override void Accept(RazorIRNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitTagHelper(this);
+        }
+
+        public override TResult Accept<TResult>(RazorIRNodeVisitor<TResult> visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            return visitor.VisitTagHelper(this);
+        }
+    }
+}

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

@@ -17,6 +17,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
         public override void Accept(ParserVisitor visitor, Span span)
         {
+            visitor.VisitAddTagHelperSpan(this, span);
         }
 
         public override void GenerateChunk(Span target, ChunkGeneratorContext context)

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

@@ -112,5 +112,25 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
         public virtual void VisitStartCommentBlock(RazorCommentChunkGenerator chunkGenerator, Block block)
         {
         }
+
+        public virtual void VisitStartTagHelperBlock(TagHelperChunkGenerator chunkGenerator, Block block)
+        {
+        }
+
+        public virtual void VisitEndTagHelperBlock(TagHelperChunkGenerator chunkGenerator, Block block)
+        {
+        }
+
+        public virtual void VisitAddTagHelperSpan(AddTagHelperChunkGenerator chunkGenerator, Span span)
+        {
+        }
+
+        public virtual void VisitRemoveTagHelperSpan(RemoveTagHelperChunkGenerator chunkGenerator, Span span)
+        {
+        }
+
+        public virtual void VisitTagHelperPrefixDirectiveSpan(TagHelperPrefixDirectiveChunkGenerator chunkGenerator, Span span)
+        {
+        }
     }
 }

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

@@ -17,6 +17,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
         public override void Accept(ParserVisitor visitor, Span span)
         {
+            visitor.VisitRemoveTagHelperSpan(this, span);
         }
 
         public override void GenerateChunk(Span target, ChunkGeneratorContext context)

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

@@ -86,10 +86,12 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
         public override void AcceptStart(ParserVisitor visitor, Block block)
         {
+            visitor.VisitStartTagHelperBlock(this, block);
         }
 
         public override void AcceptEnd(ParserVisitor visitor, Block block)
         {
+            visitor.VisitEndTagHelperBlock(this, block);
         }
     }
 }

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

@@ -17,6 +17,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
         public override void Accept(ParserVisitor visitor, Span span)
         {
+            visitor.VisitTagHelperPrefixDirectiveSpan(this, span);
         }
 
         public override void GenerateChunk(Span target, ChunkGeneratorContext context)

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

@@ -55,8 +55,8 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             // Syntax Tree passes
             builder.Features.Add(new DefaultDirectiveSyntaxTreePass());
-            builder.Features.Add(new TagHelperBinderSyntaxTreePass());
             builder.Features.Add(new HtmlNodeOptimizationPass());
+            builder.Features.Add(new TagHelperBinderSyntaxTreePass());
 
             // IR Passes
             builder.Features.Add(new DefaultDirectiveIRPass());

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

@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
     {
         public RazorEngine Engine { get; set; }
 
-        public int Order => 100;
+        public int Order => 150;
 
         public RazorSyntaxTree Execute(RazorCodeDocument document, RazorSyntaxTree syntaxTree)
         {

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

@@ -1,8 +1,6 @@
 // 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.Intermediate;
-using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests

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

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Evolution.Intermediate;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
 {
@@ -86,6 +87,31 @@ namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
             WriteContentNode(node, node.Content);
         }
 
+        internal override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+        {
+            WriteContentNode(node, node.UsedTagHelperTypeNames.ToArray());
+        }
+
+        internal override void VisitInitializeTagHelperStructure(InitializeTagHelperStructureIRNode node)
+        {
+            WriteContentNode(node, node.TagName, string.Format("{0}.{1}", nameof(TagMode), node.TagMode));
+        }
+
+        internal override void VisitCreateTagHelper(CreateTagHelperIRNode node)
+        {
+            WriteContentNode(node, node.TagHelperTypeName);
+        }
+
+        internal override void VisitSetTagHelperProperty(SetTagHelperPropertyIRNode node)
+        {
+            WriteContentNode(node, node.AttributeName, node.PropertyName, string.Format("HtmlAttributeValueStyle.{0}", node.ValueStyle));
+        }
+
+        internal override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+        {
+            WriteContentNode(node, node.Name, string.Format("{0}.{1}", nameof(HtmlAttributeValueStyle), node.ValueStyle));
+        }
+
         protected void WriteBasicNode(RazorIRNode node)
         {
             WriteIndent();

test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/TagHelpersIntegrationTest.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.Collections.Generic;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
+{
+    public class TagHelpersIntegrationTest : IntegrationTestBase
+    {
+        [Fact]
+        public void SimpleTagHelpers()
+        {
+            // Arrange
+            var descriptors = new[]
+            {
+                new TagHelperDescriptor
+                {
+                    TagName = "input",
+                    TypeName = "InputTagHelper"
+                }
+            };
+
+            var engine = RazorEngine.Create(
+                builder => builder.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(descriptors))));
+            var document = CreateCodeDocument();
+
+            // Act
+            engine.Process(document);
+
+            // Assert
+            AssertIRMatchesBaseline(document.GetIRDocument());
+        }
+
+        [Fact]
+        public void TagHelpersWithBoundAttributes()
+        {
+            // Arrange
+            var descriptors = new[]
+            {
+                new TagHelperDescriptor
+                {
+                    TagName = "input",
+                    TypeName = "InputTagHelper",
+                    Attributes = new[] { new TagHelperAttributeDescriptor
+                    {
+                        Name = "bound",
+                        PropertyName = "FooProp",
+                        TypeName = "System.String"
+                    } }
+                }
+            };
+
+            var engine = RazorEngine.Create(
+                builder => builder.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(descriptors))));
+            var document = CreateCodeDocument();
+
+            // Act
+            engine.Process(document);
+
+            // Assert
+            AssertIRMatchesBaseline(document.GetIRDocument());
+        }
+
+        [Fact]
+        public void NestedTagHelpers()
+        {
+            // Arrange
+            var descriptors = new[]
+            {
+                new TagHelperDescriptor
+                {
+                    TagName = "p",
+                    TypeName = "PTagHelper"
+                },
+                new TagHelperDescriptor
+                {
+                    TagName = "form",
+                    TypeName = "FormTagHelper"
+                },
+                new TagHelperDescriptor
+                {
+                    TagName = "input",
+                    TypeName = "InputTagHelper",
+                    Attributes = new[] { new TagHelperAttributeDescriptor
+                    {
+                        Name = "value",
+                        PropertyName = "FooProp",
+                        TypeName = "System.String"
+                    } }
+                }
+            };
+
+            var engine = RazorEngine.Create(
+                builder => builder.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(descriptors))));
+            var document = CreateCodeDocument();
+
+            // Act
+            engine.Process(document);
+
+            // Assert
+            AssertIRMatchesBaseline(document.GetIRDocument());
+        }
+
+        private class TestTagHelperDescriptorResolver : ITagHelperDescriptorResolver
+        {
+            private readonly IEnumerable<TagHelperDescriptor> _descriptors;
+
+            public TestTagHelperDescriptorResolver(IEnumerable<TagHelperDescriptor> descriptors)
+            {
+                _descriptors = descriptors;
+            }
+
+            public IEnumerable<TagHelperDescriptor> Resolve(TagHelperDescriptorResolutionContext resolutionContext)
+            {
+                return _descriptors;
+            }
+        }
+    }
+}

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

@@ -5,6 +5,9 @@ using static Microsoft.AspNetCore.Razor.Evolution.Intermediate.RazorIRAssert;
 using Xunit;
 using System;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
 {
@@ -188,9 +191,106 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
                 n => Assert.IsType<ClassDeclarationIRNode>(n));
         }
 
+        [Fact]
+        public void Lower_TagHelpers()
+        {
+            // Arrange
+            var codeDocument = TestRazorCodeDocument.Create(@"<span val=""@Hello World""></span>");
+            var descriptors = new[]
+            {
+                new TagHelperDescriptor
+                {
+                    TagName = "span",
+                    TypeName = "SpanTagHelper"
+                }
+            };
+
+            // Act
+            var irDocument = Lower(codeDocument, descriptors);
+
+            // Assert
+            Children(irDocument,
+                n => Assert.IsType<ChecksumIRNode>(n),
+                n => Assert.IsType<NamespaceDeclarationIRNode>(n));
+            var @namespace = irDocument.Children[1];
+            Children(@namespace,
+                n => Using("System", n),
+                n => Using(typeof(Task).Namespace, n),
+                n => Assert.IsType<ClassDeclarationIRNode>(n));
+            var @class = @namespace.Children[2];
+            Children(@class,
+                n => TagHelperFieldDeclaration(n, "SpanTagHelper"),
+                n => Assert.IsType<RazorMethodDeclarationIRNode>(n));
+            var method = @class.Children[1];
+            var tagHelperNode = SingleChild<TagHelperIRNode>(method);
+            Children(tagHelperNode,
+                n => TagHelperStructure("span", TagMode.StartTagAndEndTag, n),
+                n => Assert.IsType<CreateTagHelperIRNode>(n),
+                n => TagHelperHtmlAttribute(
+                    "val",
+                    HtmlAttributeValueStyle.DoubleQuotes,
+                    n,
+                    v => CSharpAttributeValue(string.Empty, "Hello", v),
+                    v => LiteralAttributeValue(" ", "World", v)),
+                n => Assert.IsType<ExecuteTagHelpersIRNode>(n));
+        }
+
+        [Fact]
+        public void Lower_TagHelpersWithBoundAttribute()
+        {
+            // Arrange
+            var codeDocument = TestRazorCodeDocument.Create("<input bound='foo' />");
+            var descriptor = new TagHelperDescriptor
+            {
+                TagName = "input",
+                TypeName = "InputTagHelper",
+                Attributes = new[] { new TagHelperAttributeDescriptor
+                {
+                    Name = "bound",
+                    PropertyName = "FooProp",
+                    TypeName = "System.String"
+                } }
+            };
+
+            // Act
+            var irDocument = Lower(codeDocument, new[] { descriptor });
+
+            // Assert
+            Children(irDocument,
+                n => Assert.IsType<ChecksumIRNode>(n),
+                n => Assert.IsType<NamespaceDeclarationIRNode>(n));
+            var @namespace = irDocument.Children[1];
+            Children(@namespace,
+                n => Using("System", n),
+                n => Using(typeof(Task).Namespace, n),
+                n => Assert.IsType<ClassDeclarationIRNode>(n));
+            var @class = @namespace.Children[2];
+            Children(@class,
+                n => TagHelperFieldDeclaration(n, "InputTagHelper"),
+                n => Assert.IsType<RazorMethodDeclarationIRNode>(n));
+            var method = @class.Children[1];
+            var tagHelperNode = SingleChild<TagHelperIRNode>(method);
+            Children(tagHelperNode,
+                n => TagHelperStructure("input", TagMode.SelfClosing, n),
+                n => Assert.IsType<CreateTagHelperIRNode>(n),
+                n => SetTagHelperProperty(
+                    "bound",
+                    "FooProp",
+                    HtmlAttributeValueStyle.SingleQuotes,
+                    n,
+                    v => Html("foo", v)),
+                n => Assert.IsType<ExecuteTagHelpersIRNode>(n));
+        }
+
         private DocumentIRNode Lower(RazorCodeDocument codeDocument)
         {
-            var engine = RazorEngine.Create();
+            return Lower(codeDocument, Enumerable.Empty<TagHelperDescriptor>());
+        }
+
+        private DocumentIRNode Lower(RazorCodeDocument codeDocument, IEnumerable<TagHelperDescriptor> descriptors)
+        {
+            var engine = RazorEngine.Create(
+                builder => builder.Features.Add(new TagHelperFeature(new TestTagHelperDescriptorResolver(descriptors))));
 
             for (var i = 0; i < engine.Phases.Count; i++)
             {
@@ -207,5 +307,20 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
             Assert.NotNull(irDocument);
             return irDocument;
         }
+
+        private class TestTagHelperDescriptorResolver : ITagHelperDescriptorResolver
+        {
+            private readonly IEnumerable<TagHelperDescriptor> _descriptors;
+
+            public TestTagHelperDescriptorResolver(IEnumerable<TagHelperDescriptor> descriptors)
+            {
+                _descriptors = descriptors;
+            }
+
+            public IEnumerable<TagHelperDescriptor> Resolve(TagHelperDescriptorResolutionContext resolutionContext)
+            {
+                return _descriptors;
+            }
+        }
     }
 }

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

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Text;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 using Xunit;
 using Xunit.Sdk;
 
@@ -188,6 +189,77 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Intermediate
             }
         }
 
+        internal static void TagHelperFieldDeclaration(RazorIRNode node, params string[] tagHelperTypes)
+        {
+            var declareTagHelperFields = Assert.IsType<DeclareTagHelperFieldsIRNode>(node);
+
+            try
+            {
+                Assert.Equal(tagHelperTypes, declareTagHelperFields.UsedTagHelperTypeNames);
+            }
+            catch (XunitException e)
+            {
+                throw new IRAssertException(declareTagHelperFields, e.Message);
+            }
+        }
+
+        internal static void TagHelperStructure(string tagName, TagMode tagMode, RazorIRNode node)
+        {
+            var tagHelperStructureNode = Assert.IsType<InitializeTagHelperStructureIRNode>(node);
+
+            try
+            {
+                Assert.Equal(tagName, tagHelperStructureNode.TagName);
+                Assert.Equal(tagMode, tagHelperStructureNode.TagMode);
+            }
+            catch (XunitException e)
+            {
+                throw new IRAssertException(tagHelperStructureNode, e.Message);
+            }
+        }
+
+        internal static void TagHelperHtmlAttribute(
+            string name,
+            HtmlAttributeValueStyle valueStyle,
+            RazorIRNode node,
+            params Action<RazorIRNode>[] valueValidators)
+        {
+            var tagHelperHtmlAttribute = Assert.IsType<AddTagHelperHtmlAttributeIRNode>(node);
+
+            try
+            {
+                Assert.Equal(name, tagHelperHtmlAttribute.Name);
+                Assert.Equal(valueStyle, tagHelperHtmlAttribute.ValueStyle);
+                Children(tagHelperHtmlAttribute, valueValidators);
+            }
+            catch (XunitException e)
+            {
+                throw new IRAssertException(tagHelperHtmlAttribute, tagHelperHtmlAttribute.Children, e.Message, e);
+            }
+        }
+
+        internal static void SetTagHelperProperty(
+            string name,
+            string propertyName,
+            HtmlAttributeValueStyle valueStyle,
+            RazorIRNode node,
+            params Action<RazorIRNode>[] valueValidators)
+        {
+            var tagHelperBoundAttribute = Assert.IsType<SetTagHelperPropertyIRNode>(node);
+
+            try
+            {
+                Assert.Equal(name, tagHelperBoundAttribute.AttributeName);
+                Assert.Equal(propertyName, tagHelperBoundAttribute.PropertyName);
+                Assert.Equal(valueStyle, tagHelperBoundAttribute.ValueStyle);
+                Children(tagHelperBoundAttribute, valueValidators);
+            }
+            catch (XunitException e)
+            {
+                throw new IRAssertException(tagHelperBoundAttribute, tagHelperBoundAttribute.Children, e.Message, e);
+            }
+        }
+
         private class IRAssertException : XunitException
         {
             public IRAssertException(RazorIRNode node, string userMessage)

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

@@ -137,8 +137,8 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             Assert.Collection(
                 features,
                 feature => Assert.IsType<DefaultDirectiveSyntaxTreePass>(feature),
-                feature => Assert.IsType<TagHelperBinderSyntaxTreePass>(feature),
                 feature => Assert.IsType<HtmlNodeOptimizationPass>(feature),
+                feature => Assert.IsType<TagHelperBinderSyntaxTreePass>(feature),
                 feature => Assert.IsType<DefaultDirectiveIRPass>(feature));
         }
 
@@ -158,8 +158,8 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             Assert.Collection(
                 features,
                 feature => Assert.IsType<DefaultDirectiveSyntaxTreePass>(feature),
-                feature => Assert.IsType<TagHelperBinderSyntaxTreePass>(feature),
                 feature => Assert.IsType<HtmlNodeOptimizationPass>(feature),
+                feature => Assert.IsType<TagHelperBinderSyntaxTreePass>(feature),
                 feature => Assert.IsType<DefaultDirectiveIRPass>(feature),
                 feature => Assert.IsType<RazorEngine.ConfigureDesignTimeOptions>(feature));
         }

test/Microsoft.AspNetCore.Razor.Evolution.Test/TestFiles/IntegrationTests/TagHelpersIntegrationTest/NestedTagHelpers.cshtml

@@ -0,0 +1,5 @@
+@addTagHelper *, TestAssembly
+<p someattr>Hola</p>
+<form unbound="foo">
+    <input value=Hello type='text' />
+</form>

test/Microsoft.AspNetCore.Razor.Evolution.Test/TestFiles/IntegrationTests/TagHelpersIntegrationTest/NestedTagHelpers.ir.txt

@@ -0,0 +1,32 @@
+Document - 
+    Checksum - 
+    NamespaceDeclaration -  - 
+        UsingStatement -  - System
+        UsingStatement -  - System.Threading.Tasks
+        ClassDeclaration -  -  -  -  - 
+            DeclareTagHelperFields -  - PTagHelper - FormTagHelper - InputTagHelper
+            RazorMethodDeclaration -  -  -  -  - 
+                HtmlContent - (0:0,0 [0] NestedTagHelpers.cshtml) - 
+                TagHelper - 
+                    InitializeTagHelperStructure -  - p - TagMode.StartTagAndEndTag
+                        HtmlContent - (43:1,12 [4] NestedTagHelpers.cshtml) - Hola
+                    CreateTagHelper -  - PTagHelper
+                    AddTagHelperHtmlAttribute -  - someattr - HtmlAttributeValueStyle.Minimized
+                    ExecuteTagHelpers - 
+                HtmlContent - (51:1,20 [2] NestedTagHelpers.cshtml) - \n
+                TagHelper - 
+                    InitializeTagHelperStructure -  - form - TagMode.StartTagAndEndTag
+                        HtmlContent - (73:2,20 [6] NestedTagHelpers.cshtml) - \n    
+                        TagHelper - 
+                            InitializeTagHelperStructure -  - input - TagMode.SelfClosing
+                            CreateTagHelper -  - InputTagHelper
+                            SetTagHelperProperty -  - value - FooProp - HtmlAttributeValueStyle.DoubleQuotes
+                                HtmlContent - (92:3,17 [5] NestedTagHelpers.cshtml) - Hello
+                            AddTagHelperHtmlAttribute -  - type - HtmlAttributeValueStyle.SingleQuotes
+                                HtmlContent - (104:3,29 [4] NestedTagHelpers.cshtml) - text
+                            ExecuteTagHelpers - 
+                        HtmlContent - (112:3,37 [2] NestedTagHelpers.cshtml) - \n
+                    CreateTagHelper -  - FormTagHelper
+                    AddTagHelperHtmlAttribute -  - unbound - HtmlAttributeValueStyle.DoubleQuotes
+                        HtmlContent - (68:2,15 [3] NestedTagHelpers.cshtml) - foo
+                    ExecuteTagHelpers - 

test/Microsoft.AspNetCore.Razor.Evolution.Test/TestFiles/IntegrationTests/TagHelpersIntegrationTest/SimpleTagHelpers.cshtml

@@ -0,0 +1,5 @@
+@addTagHelper *, TestAssembly
+<p>Hola</p>
+<form>
+    <input value='Hello' type='text' />
+</form>

test/Microsoft.AspNetCore.Razor.Evolution.Test/TestFiles/IntegrationTests/TagHelpersIntegrationTest/SimpleTagHelpers.ir.txt

@@ -0,0 +1,18 @@
+Document - 
+    Checksum - 
+    NamespaceDeclaration -  - 
+        UsingStatement -  - System
+        UsingStatement -  - System.Threading.Tasks
+        ClassDeclaration -  -  -  -  - 
+            DeclareTagHelperFields -  - InputTagHelper
+            RazorMethodDeclaration -  -  -  -  - 
+                HtmlContent - (0:0,0 [0] SimpleTagHelpers.cshtml) - <p>Hola</p>\n<form>\n    
+                TagHelper - 
+                    InitializeTagHelperStructure -  - input - TagMode.SelfClosing
+                    CreateTagHelper -  - InputTagHelper
+                    AddTagHelperHtmlAttribute -  - value - HtmlAttributeValueStyle.SingleQuotes
+                        HtmlContent - (70:3,18 [5] SimpleTagHelpers.cshtml) - Hello
+                    AddTagHelperHtmlAttribute -  - type - HtmlAttributeValueStyle.SingleQuotes
+                        HtmlContent - (83:3,31 [4] SimpleTagHelpers.cshtml) - text
+                    ExecuteTagHelpers - 
+                HtmlContent - (91:3,39 [2] SimpleTagHelpers.cshtml) - \n</form>

test/Microsoft.AspNetCore.Razor.Evolution.Test/TestFiles/IntegrationTests/TagHelpersIntegrationTest/TagHelpersWithBoundAttributes.cshtml

@@ -0,0 +1,4 @@
+@addTagHelper *, TestAssembly
+<form>
+    <input bound=@Hello type='text' />
+</form>

test/Microsoft.AspNetCore.Razor.Evolution.Test/TestFiles/IntegrationTests/TagHelpersIntegrationTest/TagHelpersWithBoundAttributes.ir.txt

@@ -0,0 +1,19 @@
+Document - 
+    Checksum - 
+    NamespaceDeclaration -  - 
+        UsingStatement -  - System
+        UsingStatement -  - System.Threading.Tasks
+        ClassDeclaration -  -  -  -  - 
+            DeclareTagHelperFields -  - InputTagHelper
+            RazorMethodDeclaration -  -  -  -  - 
+                HtmlContent - (0:0,0 [0] TagHelpersWithBoundAttributes.cshtml) - <form>\n    
+                TagHelper - 
+                    InitializeTagHelperStructure -  - input - TagMode.SelfClosing
+                    CreateTagHelper -  - InputTagHelper
+                    SetTagHelperProperty -  - bound - FooProp - HtmlAttributeValueStyle.DoubleQuotes
+                        CSharpExpression - (57:2,18 [5] TagHelpersWithBoundAttributes.cshtml)
+                            CSharpToken - (57:2,18 [5] TagHelpersWithBoundAttributes.cshtml) - Hello
+                    AddTagHelperHtmlAttribute -  - type - HtmlAttributeValueStyle.SingleQuotes
+                        HtmlContent - (69:2,30 [4] TagHelpersWithBoundAttributes.cshtml) - text
+                    ExecuteTagHelpers - 
+                HtmlContent - (77:2,38 [2] TagHelpersWithBoundAttributes.cshtml) - \n</form>