Moved AddTagHelperHtmlAttribute from renderer to writer

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

@@ -216,6 +216,11 @@ public override void VisitCreateTagHelper(CreateTagHelperIRNode node)
                 Context.TagHelperWriter.WriteCreateTagHelper(Context, node);
             }
 
+            public override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
+            {
+                Context.TagHelperWriter.WriteAddTagHelperHtmlAttribute(Context, node);
+            }
+
             public override void VisitExecuteTagHelpers(ExecuteTagHelpersIRNode node)
             {
                 Context.TagHelperWriter.WriteExecuteTagHelpers(Context, node);

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

@@ -26,7 +26,7 @@ public override void WriteDeclareTagHelperFields(CSharpRenderingContext context,
 
         public override void WriteAddTagHelperHtmlAttribute(CSharpRenderingContext context, AddTagHelperHtmlAttributeIRNode node)
         {
-            throw new NotImplementedException();
+            context.RenderChildren(node);
         }
 
         public override void WriteCreateTagHelper(CSharpRenderingContext context, CreateTagHelperIRNode node)

src/Microsoft.AspNetCore.Razor.Language/CodeGeneration/RuntimeBasicWriter.cs

@@ -13,6 +13,8 @@ public class RuntimeBasicWriter : BasicWriter
 
         public string WriteHtmlContentMethod { get; set; } = "WriteLiteral";
 
+        public string WriteAttributeValueMethod { get; set; } = "WriteAttributeValue";
+
         public override void WriteCSharpExpression(CSharpRenderingContext context, CSharpExpressionIRNode node)
         {
             if (context == null)

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

@@ -278,77 +278,6 @@ public override void VisitAddPreallocatedTagHelperHtmlAttribute(AddPreallocatedT
                 .WriteEndMethodInvocation();
         }
 
-        public override void VisitAddTagHelperHtmlAttribute(AddTagHelperHtmlAttributeIRNode node)
-        {
-            var attributeValueStyleParameter = $"global::Microsoft.AspNetCore.Razor.TagHelpers.HtmlAttributeValueStyle.{node.ValueStyle}";
-            var isConditionalAttributeValue = node.Children.Any(child => child is CSharpAttributeValueIRNode);
-
-            // All simple text and minimized attributes will be pre-allocated.
-            if (isConditionalAttributeValue)
-            {
-                // Dynamic attribute value should be run through the conditional attribute removal system. It's
-                // unbound and contains C#.
-
-                // TagHelper attribute rendering is buffered by default. We do not want to write to the current
-                // writer.
-                var valuePieceCount = node.Children.Count(
-                    child => child is HtmlAttributeValueIRNode || child is CSharpAttributeValueIRNode);
-
-                Context.Writer
-                    .WriteStartMethodInvocation("BeginAddHtmlAttributeValues" /* ORIGINAL: BeginAddHtmlAttributeValuesMethodName */)
-                    .Write("__tagHelperExecutionContext" /* ORIGINAL: ExecutionContextVariableName */)
-                    .WriteParameterSeparator()
-                    .WriteStringLiteral(node.Name)
-                    .WriteParameterSeparator()
-                    .Write(valuePieceCount.ToString(CultureInfo.InvariantCulture))
-                    .WriteParameterSeparator()
-                    .Write(attributeValueStyleParameter)
-                    .WriteEndMethodInvocation();
-
-                var initialRenderingConventions = Context.RenderingConventions;
-                Context.RenderingConventions = new TagHelperHtmlAttributeRenderingConventions(Context.Writer);
-                VisitDefault(node);
-                Context.RenderingConventions = initialRenderingConventions;
-
-                Context.Writer
-                    .WriteMethodInvocation(
-                        "EndAddHtmlAttributeValues" /* ORIGINAL: EndAddHtmlAttributeValuesMethodName */,
-                        "__tagHelperExecutionContext" /* ORIGINAL: ExecutionContextVariableName */);
-            }
-            else
-            {
-                // This is a data-* attribute which includes C#. Do not perform the conditional attribute removal or
-                // other special cases used when IsDynamicAttributeValue(). But the attribute must still be buffered to
-                // determine its final value.
-
-                // Attribute value is not plain text, must be buffered to determine its final value.
-                Context.Writer.WriteMethodInvocation("BeginWriteTagHelperAttribute" /* ORIGINAL: BeginWriteTagHelperAttributeMethodName */);
-
-                // We're building a writing scope around the provided chunks which captures everything written from the
-                // page. Therefore, we do not want to write to any other buffer since we're using the pages buffer to
-                // ensure we capture all content that's written, directly or indirectly.
-                var initialRenderingConventions = Context.RenderingConventions;
-                Context.RenderingConventions = new CSharpRenderingConventions(Context.Writer);
-                VisitDefault(node);
-                Context.RenderingConventions = initialRenderingConventions;
-
-                Context.Writer
-                    .WriteStartAssignment("__tagHelperStringValueBuffer" /* ORIGINAL: StringValueBufferVariableName */)
-                    .WriteMethodInvocation("EndWriteTagHelperAttribute" /* ORIGINAL: EndWriteTagHelperAttributeMethodName */)
-                    .WriteStartInstanceMethodInvocation(
-                        "__tagHelperExecutionContext" /* ORIGINAL: ExecutionContextVariableName */,
-                        "AddHtmlAttribute" /* ORIGINAL: ExecutionContextAddHtmlAttributeMethodName */)
-                    .WriteStringLiteral(node.Name)
-                    .WriteParameterSeparator()
-                    .WriteStartMethodInvocation("Html.Raw" /* ORIGINAL: MarkAsHtmlEncodedMethodName */)
-                    .Write("__tagHelperStringValueBuffer" /* ORIGINAL: StringValueBufferVariableName */)
-                    .WriteEndMethodInvocation(endLine: false)
-                    .WriteParameterSeparator()
-                    .Write(attributeValueStyleParameter)
-                    .WriteEndMethodInvocation();
-            }
-        }
-
         public override void VisitSetPreallocatedTagHelperProperty(SetPreallocatedTagHelperPropertyIRNode node)
         {
             var tagHelperVariableName = GetTagHelperVariableName(node.TagHelperTypeName);

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

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Globalization;
+using System.Linq;
 using Microsoft.AspNetCore.Razor.Language.Intermediate;
 
 namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
@@ -20,6 +22,8 @@ public class RuntimeTagHelperWriter : TagHelperWriter
 
         public string ExecutionContextSetOutputContentAsyncMethodName { get; set; } = "SetOutputContentAsync";
 
+        public string ExecutionContextAddHtmlAttributeMethodName { get; set; } = "AddHtmlAttribute";
+
         public string RunnerTypeName { get; set; } = "global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner";
 
         public string RunnerVariableName { get; set; } = "__tagHelperRunner";
@@ -44,6 +48,16 @@ public class RuntimeTagHelperWriter : TagHelperWriter
 
         public string TagHelperOutputIsContentModifiedPropertyName { get; set; } = "IsContentModified";
 
+        public string BeginAddHtmlAttributeValuesMethodName { get; set; } = "BeginAddHtmlAttributeValues";
+
+        public string EndAddHtmlAttributeValuesMethodName { get; set; } = "EndAddHtmlAttributeValues";
+
+        public string BeginWriteTagHelperAttributeMethodName { get; set; } = "BeginWriteTagHelperAttribute";
+
+        public string EndWriteTagHelperAttributeMethodName { get; set; } = "EndWriteTagHelperAttribute";
+
+        public string MarkAsHtmlEncodedMethodName { get; set; } = "Html.Raw";
+
         public string WriteTagHelperOutputMethod { get; set; } = "Write";
 
         public override void WriteDeclareTagHelperFields(CSharpRenderingContext context, DeclareTagHelperFieldsIRNode node)
@@ -127,7 +141,82 @@ public override void WriteDeclareTagHelperFields(CSharpRenderingContext context,
 
         public override void WriteAddTagHelperHtmlAttribute(CSharpRenderingContext context, AddTagHelperHtmlAttributeIRNode node)
         {
-            throw new NotImplementedException();
+            var attributeValueStyleParameter = $"global::Microsoft.AspNetCore.Razor.TagHelpers.HtmlAttributeValueStyle.{node.ValueStyle}";
+            var isConditionalAttributeValue = node.Children.Any(child => child is CSharpAttributeValueIRNode);
+
+            // All simple text and minimized attributes will be pre-allocated.
+            if (isConditionalAttributeValue)
+            {
+                // Dynamic attribute value should be run through the conditional attribute removal system. It's
+                // unbound and contains C#.
+
+                // TagHelper attribute rendering is buffered by default. We do not want to write to the current
+                // writer.
+                var valuePieceCount = node.Children.Count(
+                    child => child is HtmlAttributeValueIRNode || child is CSharpAttributeValueIRNode);
+
+                context.Writer
+                    .WriteStartMethodInvocation(BeginAddHtmlAttributeValuesMethodName)
+                    .Write(ExecutionContextVariableName)
+                    .WriteParameterSeparator()
+                    .WriteStringLiteral(node.Name)
+                    .WriteParameterSeparator()
+                    .Write(valuePieceCount.ToString(CultureInfo.InvariantCulture))
+                    .WriteParameterSeparator()
+                    .Write(attributeValueStyleParameter)
+                    .WriteEndMethodInvocation();
+
+                // This can be removed once all the tag helper nodes are moved out of the renderers.
+                var initialRenderingConventions = context.RenderingConventions;
+                context.RenderingConventions = new TagHelperHtmlAttributeRenderingConventions(context.Writer);
+                using (context.Push(new TagHelperHtmlAttributeRuntimeBasicWriter()))
+                {
+                    context.RenderChildren(node);
+                }
+                context.RenderingConventions = initialRenderingConventions;
+
+                context.Writer
+                    .WriteMethodInvocation(
+                        EndAddHtmlAttributeValuesMethodName,
+                        ExecutionContextVariableName);
+            }
+            else
+            {
+                // This is a data-* attribute which includes C#. Do not perform the conditional attribute removal or
+                // other special cases used when IsDynamicAttributeValue(). But the attribute must still be buffered to
+                // determine its final value.
+
+                // Attribute value is not plain text, must be buffered to determine its final value.
+                context.Writer.WriteMethodInvocation(BeginWriteTagHelperAttributeMethodName);
+
+                // We're building a writing scope around the provided chunks which captures everything written from the
+                // page. Therefore, we do not want to write to any other buffer since we're using the pages buffer to
+                // ensure we capture all content that's written, directly or indirectly.
+                // This can be removed once all the tag helper nodes are moved out of the renderers.
+                var initialRenderingConventions = context.RenderingConventions;
+                context.RenderingConventions = new CSharpRenderingConventions(context.Writer);
+                using (context.Push(new RuntimeBasicWriter()))
+                using (context.Push(new RuntimeTagHelperWriter()))
+                {
+                    context.RenderChildren(node);
+                }
+                context.RenderingConventions = initialRenderingConventions;
+
+                context.Writer
+                    .WriteStartAssignment(StringValueBufferVariableName)
+                    .WriteMethodInvocation(EndWriteTagHelperAttributeMethodName)
+                    .WriteStartInstanceMethodInvocation(
+                        ExecutionContextVariableName,
+                        ExecutionContextAddHtmlAttributeMethodName)
+                    .WriteStringLiteral(node.Name)
+                    .WriteParameterSeparator()
+                    .WriteStartMethodInvocation(MarkAsHtmlEncodedMethodName)
+                    .Write(StringValueBufferVariableName)
+                    .WriteEndMethodInvocation(endLine: false)
+                    .WriteParameterSeparator()
+                    .Write(attributeValueStyleParameter)
+                    .WriteEndMethodInvocation();
+            }
         }
 
         public override void WriteCreateTagHelper(CSharpRenderingContext context, CreateTagHelperIRNode node)

src/Microsoft.AspNetCore.Razor.Language/CodeGeneration/TagHelperHtmlAttributeRuntimeBasicWriter.cs

@@ -0,0 +1,11 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
+{
+    internal class TagHelperHtmlAttributeRuntimeBasicWriter : RuntimeBasicWriter
+    {
+        // This will be used when HtmlAttributeValueIRNode and CSharpAttributeValueIRNode are moved to writers.
+        public new string WriteAttributeValueMethod { get; set; } = "AddHtmlAttributeValue";
+    }
+}