Moved ExecuteTagHelpersIRNode from renderer to writer

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/CSharpRenderingContext.cs

@@ -96,7 +96,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
                 throw new ArgumentNullException(nameof(writer));
             }
 
-            var scope = new TagHelperWriterScope(this, BasicWriter);
+            var scope = new TagHelperWriterScope(this, TagHelperWriter);
             TagHelperWriter = writer;
             return scope;
         }
@@ -131,9 +131,9 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
         public struct TagHelperWriterScope : IDisposable
         {
             private readonly CSharpRenderingContext _context;
-            private readonly BasicWriter _writer;
+            private readonly TagHelperWriter _writer;
 
-            public TagHelperWriterScope(CSharpRenderingContext context, BasicWriter writer)
+            public TagHelperWriterScope(CSharpRenderingContext context, TagHelperWriter writer)
             {
                 if (context == null)
                 {
@@ -151,7 +151,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 
             public void Dispose()
             {
-                _context.BasicWriter = _writer;
+                _context.TagHelperWriter = _writer;
             }
         }
     }

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/DefaultDocumentWriter.cs

@@ -211,6 +211,11 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
                 Context.TagHelperWriter.WriteCreateTagHelper(Context, node);
             }
 
+            public override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
+            {
+                Context.TagHelperWriter.WriteExecuteTagHelpers(Context, node);
+            }
+
             public override void VisitDefault(RazorIRNode node)
             {
                 // This is a temporary bridge to the renderer, which allows us to move functionality piecemeal

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/DesignTimeTagHelperWriter.cs

@@ -43,7 +43,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 
         public override void WriteExecuteTagHelpers(CSharpRenderingContext context, ExecuteTagHelpersIRNode node)
         {
-            throw new NotImplementedException();
+            // Do nothing
         }
 
         public override void WriteInitializeTagHelperStructure(CSharpRenderingContext context, InitializeTagHelperStructureIRNode node)

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/RedirectedTagHelperWriter.cs

@@ -0,0 +1,108 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
+{
+    internal class RedirectedTagHelperWriter : TagHelperWriter
+    {
+        private readonly TagHelperWriter _previous;
+        private readonly string _textWriter;
+
+        public RedirectedTagHelperWriter(TagHelperWriter previous, string textWriter)
+        {
+            _previous = previous;
+            _textWriter = textWriter;
+        }
+
+        public string ExecutionContextVariableName { get; set; } = "__tagHelperExecutionContext";
+
+        public string ExecutionContextOutputPropertyName { get; set; } = "Output";
+
+        public string ExecutionContextSetOutputContentAsyncMethodName { get; set; } = "SetOutputContentAsync";
+
+        public string RunnerVariableName { get; set; } = "__tagHelperRunner";
+
+        public string RunnerRunAsyncMethodName { get; set; } = "RunAsync";
+
+        public string ScopeManagerVariableName { get; set; } = "__tagHelperScopeManager";
+
+        public string ScopeManagerEndMethodName { get; set; } = "End";
+
+        public string TagHelperOutputIsContentModifiedPropertyName { get; set; } = "IsContentModified";
+
+        public string WriteTagHelperOutputMethod { get; set; } = "WriteTo";
+
+        public override void WriteAddTagHelperHtmlAttribute(CSharpRenderingContext context, AddTagHelperHtmlAttributeIRNode node)
+        {
+            _previous.WriteAddTagHelperHtmlAttribute(context, node);
+        }
+
+        public override void WriteCreateTagHelper(CSharpRenderingContext context, CreateTagHelperIRNode node)
+        {
+            _previous.WriteCreateTagHelper(context, node);
+        }
+
+        public override void WriteDeclareTagHelperFields(CSharpRenderingContext context, DeclareTagHelperFieldsIRNode node)
+        {
+            _previous.WriteDeclareTagHelperFields(context, node);
+        }
+
+        public override void WriteExecuteTagHelpers(CSharpRenderingContext context, ExecuteTagHelpersIRNode node)
+        {
+            if (context.Options.DesignTimeMode)
+            {
+                _previous.WriteExecuteTagHelpers(context, node);
+                return;
+            }
+
+            context.Writer
+                .Write("await ")
+                .WriteStartInstanceMethodInvocation(
+                    RunnerVariableName,
+                    RunnerRunAsyncMethodName)
+                .Write(ExecutionContextVariableName)
+                .WriteEndMethodInvocation();
+
+            var tagHelperOutputAccessor = $"{ExecutionContextVariableName}.{ExecutionContextOutputPropertyName}";
+
+            context.Writer
+                .Write("if (!")
+                .Write(tagHelperOutputAccessor)
+                .Write(".")
+                .Write(TagHelperOutputIsContentModifiedPropertyName)
+                .WriteLine(")");
+
+            using (context.Writer.BuildScope())
+            {
+                context.Writer
+                    .Write("await ")
+                    .WriteInstanceMethodInvocation(
+                        ExecutionContextVariableName,
+                        ExecutionContextSetOutputContentAsyncMethodName);
+            }
+
+            context.Writer
+                .WriteStartMethodInvocation(WriteTagHelperOutputMethod)
+                .Write(_textWriter)
+                .WriteParameterSeparator()
+                .Write(tagHelperOutputAccessor)
+                .WriteEndMethodInvocation()
+                .WriteStartAssignment(ExecutionContextVariableName)
+                .WriteInstanceMethodInvocation(
+                    ScopeManagerVariableName,
+                    ScopeManagerEndMethodName);
+        }
+
+        public override void WriteInitializeTagHelperStructure(CSharpRenderingContext context, InitializeTagHelperStructureIRNode node)
+        {
+            _previous.WriteInitializeTagHelperStructure(context, node);
+        }
+
+        public override void WriteSetTagHelperProperty(CSharpRenderingContext context, SetTagHelperPropertyIRNode node)
+        {
+            _previous.WriteSetTagHelperProperty(context, node);
+        }
+    }
+}

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/RuntimeCSharpRenderer.cs

@@ -456,46 +456,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
                 .WriteEndMethodInvocation();
         }
 
-        public override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
-        {
-            Context.Writer
-                .Write("await ")
-                .WriteStartInstanceMethodInvocation(
-                    "__tagHelperRunner" /* ORIGINAL: RunnerVariableName */,
-                    "RunAsync" /* ORIGINAL: RunnerRunAsyncMethodName */)
-                .Write("__tagHelperExecutionContext" /* ORIGINAL: ExecutionContextVariableName */)
-                .WriteEndMethodInvocation();
-
-            var executionContextVariableName = "__tagHelperExecutionContext" /* ORIGINAL: ExecutionContextVariableName */;
-            var executionContextOutputPropertyName = "Output" /* ORIGINAL: ExecutionContextOutputPropertyName */;
-            var tagHelperOutputAccessor = $"{executionContextVariableName}.{executionContextOutputPropertyName}";
-
-            Context.Writer
-                .Write("if (!")
-                .Write(tagHelperOutputAccessor)
-                .Write(".")
-                .Write("IsContentModified" /* ORIGINAL: TagHelperOutputIsContentModifiedPropertyName */)
-                .WriteLine(")");
-
-            using (Context.Writer.BuildScope())
-            {
-                Context.Writer
-                    .Write("await ")
-                    .WriteInstanceMethodInvocation(
-                        executionContextVariableName,
-                        "SetOutputContentAsync" /* ORIGINAL: ExecutionContextSetOutputContentAsyncMethodName */);
-            }
-
-            Context.Writer
-                .Write(Context.RenderingConventions.StartWriteMethod)
-                .Write(tagHelperOutputAccessor)
-                .WriteEndMethodInvocation()
-                .WriteStartAssignment(executionContextVariableName)
-                .WriteInstanceMethodInvocation(
-                    "__tagHelperScopeManager" /* ORIGINAL: ScopeManagerVariableName */,
-                    "End" /* ORIGINAL: ScopeManagerEndMethodName */);
-        }
-
         public override void VisitDeclarePreallocatedTagHelperHtmlAttribute(DeclarePreallocatedTagHelperHtmlAttributeIRNode node)
         {
             Context.Writer

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/RuntimeTagHelperWriter.cs

@@ -16,16 +16,24 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 
         public string ExecutionContextAddMethodName { get; set; } = "Add";
 
+        public string ExecutionContextOutputPropertyName { get; set; } = "Output";
+
+        public string ExecutionContextSetOutputContentAsyncMethodName { get; set; } = "SetOutputContentAsync";
+
         public string RunnerTypeName { get; set; } = "global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner";
 
         public string RunnerVariableName { get; set; } = "__tagHelperRunner";
 
+        public string RunnerRunAsyncMethodName { get; set; } = "RunAsync";
+
         public string ScopeManagerTypeName { get; set; } = "global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager";
 
         public string ScopeManagerVariableName { get; set; } = "__tagHelperScopeManager";
 
         public string ScopeManagerBeginMethodName { get; set; } = "Begin";
 
+        public string ScopeManagerEndMethodName { get; set; } = "End";
+
         public string StartTagHelperWritingScopeMethodName { get; set; } = "StartTagHelperWritingScope";
 
         public string EndTagHelperWritingScopeMethodName { get; set; } = "EndTagHelperWritingScope";
@@ -34,6 +42,10 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 
         public string CreateTagHelperMethodName { get; set; } = "CreateTagHelper";
 
+        public string TagHelperOutputIsContentModifiedPropertyName { get; set; } = "IsContentModified";
+
+        public string WriteTagHelperOutputMethod { get; set; } = "Write";
+
         public override void WriteDeclareTagHelperFields(CSharpRenderingContext context, DeclareTagHelperFieldsIRNode node)
         {
             context.Writer.WriteLineHiddenDirective();
@@ -137,7 +149,40 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 
         public override void WriteExecuteTagHelpers(CSharpRenderingContext context, ExecuteTagHelpersIRNode node)
         {
-            throw new NotImplementedException();
+            context.Writer
+                .Write("await ")
+                .WriteStartInstanceMethodInvocation(
+                    RunnerVariableName,
+                    RunnerRunAsyncMethodName)
+                .Write(ExecutionContextVariableName)
+                .WriteEndMethodInvocation();
+
+            var tagHelperOutputAccessor = $"{ExecutionContextVariableName}.{ExecutionContextOutputPropertyName}";
+
+            context.Writer
+                .Write("if (!")
+                .Write(tagHelperOutputAccessor)
+                .Write(".")
+                .Write(TagHelperOutputIsContentModifiedPropertyName)
+                .WriteLine(")");
+
+            using (context.Writer.BuildScope())
+            {
+                context.Writer
+                    .Write("await ")
+                    .WriteInstanceMethodInvocation(
+                        ExecutionContextVariableName,
+                        ExecutionContextSetOutputContentAsyncMethodName);
+            }
+
+            context.Writer
+                .WriteStartMethodInvocation(WriteTagHelperOutputMethod)
+                .Write(tagHelperOutputAccessor)
+                .WriteEndMethodInvocation()
+                .WriteStartAssignment(ExecutionContextVariableName)
+                .WriteInstanceMethodInvocation(
+                    ScopeManagerVariableName,
+                    ScopeManagerEndMethodName);
         }
 
         public override void WriteInitializeTagHelperStructure(CSharpRenderingContext context, InitializeTagHelperStructureIRNode node)
@@ -167,6 +212,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
             context.RenderingConventions = new CSharpRenderingConventions(context.Writer);
 
             using (context.Push(new RuntimeBasicWriter()))
+            using (context.Push(new RuntimeTagHelperWriter()))
             {
                 using (context.Writer.BuildAsyncLambda(endLine: false))
                 {

src/Microsoft.AspNetCore.Razor.Evolution/CodeGeneration/TemplateTargetExtension.cs

@@ -24,6 +24,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
             context.RenderingConventions = new CSharpRedirectRenderingConventions(TemplateWriterName, context.Writer);
 
             using (context.Push(new RedirectedBasicWriter(context.BasicWriter, TemplateWriterName)))
+            using (context.Push(new RedirectedTagHelperWriter(context.TagHelperWriter, TemplateWriterName)))
             {
                 using (context.Writer.BuildAsyncLambda(endLine: false, parameterNames: TemplateWriterName))
                 {

test/Microsoft.AspNetCore.Razor.Evolution.Test/CodeGeneration/RedirectedTagHelperWriterTest.cs

@@ -0,0 +1,76 @@
+// 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.Intermediate;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
+{
+    public class RedirectedTagHelperWriterTest
+    {
+        // In design time this will not include the 'text writer' parameter.
+        [Fact]
+        public void WriteExecuteTagHelpers_DesignTime_DoesNormalWrite()
+        {
+            // Arrange
+            var writer = new RedirectedTagHelperWriter(new DesignTimeTagHelperWriter(), "test_writer")
+            {
+                WriteTagHelperOutputMethod = "Test",
+            };
+
+            var context = new CSharpRenderingContext()
+            {
+                Options = RazorParserOptions.CreateDefaultOptions(),
+                Writer = new Legacy.CSharpCodeWriter(),
+            };
+
+            context.Options.DesignTimeMode = true;
+
+            var node = new ExecuteTagHelpersIRNode();
+
+            // Act
+            writer.WriteExecuteTagHelpers(context, node);
+
+            // Assert
+            var csharp = context.Writer.Builder.ToString();
+            Assert.Empty(csharp);
+        }
+
+        [Fact]
+        public void WriteExecuteTagHelpers_Runtime_RendersWithRedirectWriter()
+        {
+            // Arrange
+            var writer = new RedirectedTagHelperWriter(new RuntimeTagHelperWriter(), "test_writer")
+            {
+                WriteTagHelperOutputMethod = "Test",
+            };
+
+            var context = new CSharpRenderingContext()
+            {
+                Options = RazorParserOptions.CreateDefaultOptions(),
+                Writer = new Legacy.CSharpCodeWriter(),
+            };
+
+            var node = new ExecuteTagHelpersIRNode();
+
+            // Act
+            writer.WriteExecuteTagHelpers(context, node);
+
+            // Assert
+            var csharp = context.Writer.Builder.ToString();
+            Assert.Equal(
+@"await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
+if (!__tagHelperExecutionContext.Output.IsContentModified)
+{
+    await __tagHelperExecutionContext.SetOutputContentAsync();
+}
+Test(test_writer, __tagHelperExecutionContext.Output);
+__tagHelperExecutionContext = __tagHelperScopeManager.End();
+",
+                csharp,
+                ignoreLineEndingDifferences: true);
+        }
+    }
+}

test/Microsoft.AspNetCore.Razor.Evolution.Test/CodeGeneration/RuntimeTagHelperWriterTest.cs

@@ -101,6 +101,7 @@ private global::MyTagHelper __MyTagHelper = null;
             {
                 Writer = new Legacy.CSharpCodeWriter(),
                 BasicWriter = new RuntimeBasicWriter(),
+                TagHelperWriter = new RuntimeTagHelperWriter(),
                 IdGenerator = () => "test",
                 RenderChildren = n => { }
             };
@@ -146,6 +147,35 @@ private global::MyTagHelper __MyTagHelper = null;
             Assert.Equal(
 @"__TestNamespace_MyTagHelper = CreateTagHelper<global::TestNamespace.MyTagHelper>();
 __tagHelperExecutionContext.Add(__TestNamespace_MyTagHelper);
+",
+                csharp,
+                ignoreLineEndingDifferences: true);
+        }
+
+        [Fact]
+        public void WriteExecuteTagHelpers_RendersCorrectly()
+        {
+            // Arrange
+            var writer = new RuntimeTagHelperWriter();
+            var context = new CSharpRenderingContext()
+            {
+                Writer = new Legacy.CSharpCodeWriter(),
+            };
+            var node = new ExecuteTagHelpersIRNode();
+
+            // Act
+            writer.WriteExecuteTagHelpers(context, node);
+
+            // Assert
+            var csharp = context.Writer.Builder.ToString();
+            Assert.Equal(
+@"await __tagHelperRunner.RunAsync(__tagHelperExecutionContext);
+if (!__tagHelperExecutionContext.Output.IsContentModified)
+{
+    await __tagHelperExecutionContext.SetOutputContentAsync();
+}
+Write(__tagHelperExecutionContext.Output);
+__tagHelperExecutionContext = __tagHelperScopeManager.End();
 ",
                 csharp,
                 ignoreLineEndingDifferences: true);

test/Microsoft.AspNetCore.Razor.Evolution.Test/CodeGeneration/TemplateTargetExtensionTest.cs

@@ -23,6 +23,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
             var context = new CSharpRenderingContext()
             { 
                 BasicWriter = new RuntimeBasicWriter(),
+                TagHelperWriter = new RuntimeTagHelperWriter(),
                 Writer = new CSharpCodeWriter(),
             };