Moved DeclareTagHelperFields from renderer to writer

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

@@ -46,7 +46,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
             _context.RenderNode = visitor.Visit;
 
             _context.BasicWriter = _context.Options.DesignTimeMode ? (BasicWriter)new DesignTimeBasicWriter() : new RuntimeBasicWriter();
-            _context.TagHelperWriter = new DefaultTagHelperWriter();
+            _context.TagHelperWriter = _context.Options.DesignTimeMode ? (TagHelperWriter)new DesignTimeTagHelperWriter() : new RuntimeTagHelperWriter();
 
             visitor.VisitDocument(node);
             _context.RenderChildren = null;
@@ -188,6 +188,11 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
                 Context.BasicWriter.WriteCSharpStatement(Context, node);
             }
 
+            public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
+            {
+                Context.TagHelperWriter.WriteDeclareTagHelperFields(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/DesignTimeBasicWriter.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Linq;
 using Microsoft.AspNetCore.Razor.Evolution.Intermediate;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration

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

@@ -316,20 +316,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
             }
         }
 
-        public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
-        {
-            foreach (var tagHelperTypeName in node.UsedTagHelperTypeNames)
-            {
-                var tagHelperVariableName = GetTagHelperVariableName(tagHelperTypeName);
-                Context.Writer
-                    .Write("private global::")
-                    .WriteVariableDeclaration(
-                        tagHelperTypeName,
-                        tagHelperVariableName,
-                        value: null);
-            }
-        }
-
         private void RenderTagHelperAttributeInline(
             RazorIRNode node,
             SourceSpan documentLocation)

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

@@ -6,8 +6,22 @@ using Microsoft.AspNetCore.Razor.Evolution.Intermediate;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 {
-    public class DefaultTagHelperWriter : TagHelperWriter
+    public class DesignTimeTagHelperWriter : TagHelperWriter
     {
+        public override void WriteDeclareTagHelperFields(CSharpRenderingContext context, DeclareTagHelperFieldsIRNode node)
+        {
+            foreach (var tagHelperTypeName in node.UsedTagHelperTypeNames)
+            {
+                var tagHelperVariableName = GetTagHelperVariableName(tagHelperTypeName);
+                context.Writer
+                    .Write("private global::")
+                    .WriteVariableDeclaration(
+                        tagHelperTypeName,
+                        tagHelperVariableName,
+                        value: null);
+            }
+        }
+
         public override void WriteAddTagHelperHtmlAttribute(CSharpRenderingContext context, AddTagHelperHtmlAttributeIRNode node)
         {
             throw new NotImplementedException();
@@ -32,5 +46,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
         {
             throw new NotImplementedException();
         }
+
+        private static string GetTagHelperVariableName(string tagHelperTypeName) => "__" + tagHelperTypeName.Replace('.', '_');
     }
 }

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

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Linq;
 using Microsoft.AspNetCore.Razor.Evolution.Intermediate;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration

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

@@ -601,85 +601,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
                 .WriteEndMethodInvocation();
         }
 
-        public override void VisitDeclareTagHelperFields(DeclareTagHelperFieldsIRNode node)
-        {
-            Context.Writer.WriteLineHiddenDirective();
-
-            // Need to disable the warning "X is assigned to but never used." for the value buffer since
-            // whether it's used depends on how a TagHelper is used.
-            Context.Writer
-                .WritePragma("warning disable 0414")
-                .Write("private ")
-                .WriteVariableDeclaration("string", "__tagHelperStringValueBuffer" /* ORIGINAL: StringValueBufferVariableName */, value: null)
-                .WritePragma("warning restore 0414");
-
-            Context.Writer
-            .Write("private global::")
-            .WriteVariableDeclaration(
-                "Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext" /* ORIGINAL: ExecutionContextTypeName */,
-                "__tagHelperExecutionContext" /* ORIGINAL: ExecutionContextVariableName */,
-                value: null);
-
-            Context.Writer
-            .Write("private global::")
-            .Write("Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner" /* ORIGINAL: RunnerTypeName */)
-            .Write(" ")
-            .Write("__tagHelperRunner" /* ORIGINAL: RunnerVariableName */)
-            .Write(" = new global::")
-            .Write("Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner" /* ORIGINAL: RunnerTypeName */)
-            .WriteLine("();");
-
-            const string backedScopeManageVariableName = "__backed" + "__tagHelperScopeManager" /* ORIGINAL: ScopeManagerVariableName */;
-            Context.Writer
-                .Write("private global::")
-                .WriteVariableDeclaration(
-                    "Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager",
-                    backedScopeManageVariableName,
-                    value: null);
-
-            Context.Writer
-            .Write("private global::")
-            .Write("Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager" /* ORIGINAL: ScopeManagerTypeName */)
-            .Write(" ")
-            .WriteLine("__tagHelperScopeManager" /* ORIGINAL: ScopeManagerVariableName */);
-
-            using (Context.Writer.BuildScope())
-            {
-                Context.Writer.WriteLine("get");
-                using (Context.Writer.BuildScope())
-                {
-                    Context.Writer
-                        .Write("if (")
-                        .Write(backedScopeManageVariableName)
-                        .WriteLine(" == null)");
-
-                    using (Context.Writer.BuildScope())
-                    {
-                        Context.Writer
-                            .WriteStartAssignment(backedScopeManageVariableName)
-                            .WriteStartNewObject("Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager" /* ORIGINAL: ScopeManagerTypeName */)
-                            .Write("StartTagHelperWritingScope" /* ORIGINAL: StartTagHelperWritingScopeMethodName */)
-                            .WriteParameterSeparator()
-                            .Write("EndTagHelperWritingScope" /* ORIGINAL: EndTagHelperWritingScopeMethodName */)
-                            .WriteEndMethodInvocation();
-                    }
-
-                    Context.Writer.WriteReturn(backedScopeManageVariableName);
-                }
-            }
-
-            foreach (var tagHelperTypeName in node.UsedTagHelperTypeNames)
-            {
-                var tagHelperVariableName = GetTagHelperVariableName(tagHelperTypeName);
-                Context.Writer
-                    .Write("private global::")
-                    .WriteVariableDeclaration(
-                        tagHelperTypeName,
-                        tagHelperVariableName,
-                        value: null);
-            }
-        }
-
         private void RenderTagHelperAttributeInline(
             RazorIRNode node,
             SourceSpan documentLocation)

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

@@ -0,0 +1,135 @@
+// 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 Microsoft.AspNetCore.Razor.Evolution.Intermediate;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
+{
+    public class RuntimeTagHelperWriter : TagHelperWriter
+    {
+        public string StringValueBufferVariableName { get; set; } = "__tagHelperStringValueBuffer";
+
+        public string ExecutionContextTypeName { get; set; } = "Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext";
+
+        public string ExecutionContextVariableName { get; set; } = "__tagHelperExecutionContext";
+
+        public string RunnerTypeName { get; set; } = "Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner";
+
+        public string RunnerVariableName { get; set; } = "__tagHelperRunner";
+
+        public string ScopeManagerTypeName { get; set; } = "Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager";
+
+        public string ScopeManagerVariableName { get; set; } = "__tagHelperScopeManager";
+
+        public string StartTagHelperWritingScopeMethodName { get; set; } = "StartTagHelperWritingScope";
+
+        public string EndTagHelperWritingScopeMethodName { get; set; } = "EndTagHelperWritingScope";
+
+        public override void WriteDeclareTagHelperFields(CSharpRenderingContext context, DeclareTagHelperFieldsIRNode node)
+        {
+            context.Writer.WriteLineHiddenDirective();
+
+            // Need to disable the warning "X is assigned to but never used." for the value buffer since
+            // whether it's used depends on how a TagHelper is used.
+            context.Writer
+                .WritePragma("warning disable 0414")
+                .Write("private ")
+                .WriteVariableDeclaration("string", StringValueBufferVariableName, value: null)
+                .WritePragma("warning restore 0414");
+
+            context.Writer
+            .Write("private global::")
+            .WriteVariableDeclaration(
+                ExecutionContextTypeName,
+                ExecutionContextVariableName,
+                value: null);
+
+            context.Writer
+            .Write("private global::")
+            .Write(RunnerTypeName)
+            .Write(" ")
+            .Write(RunnerVariableName)
+            .Write(" = new global::")
+            .Write(RunnerTypeName)
+            .WriteLine("();");
+
+            var backedScopeManageVariableName = "__backed" + ScopeManagerVariableName;
+            context.Writer
+                .Write("private global::")
+                .WriteVariableDeclaration(
+                    ScopeManagerTypeName,
+                    backedScopeManageVariableName,
+                    value: null);
+
+            context.Writer
+            .Write("private global::")
+            .Write(ScopeManagerTypeName)
+            .Write(" ")
+            .WriteLine(ScopeManagerVariableName);
+
+            using (context.Writer.BuildScope())
+            {
+                context.Writer.WriteLine("get");
+                using (context.Writer.BuildScope())
+                {
+                    context.Writer
+                        .Write("if (")
+                        .Write(backedScopeManageVariableName)
+                        .WriteLine(" == null)");
+
+                    using (context.Writer.BuildScope())
+                    {
+                        context.Writer
+                            .WriteStartAssignment(backedScopeManageVariableName)
+                            .WriteStartNewObject(ScopeManagerTypeName)
+                            .Write(StartTagHelperWritingScopeMethodName)
+                            .WriteParameterSeparator()
+                            .Write(EndTagHelperWritingScopeMethodName)
+                            .WriteEndMethodInvocation();
+                    }
+
+                    context.Writer.WriteReturn(backedScopeManageVariableName);
+                }
+            }
+
+            foreach (var tagHelperTypeName in node.UsedTagHelperTypeNames)
+            {
+                var tagHelperVariableName = GetTagHelperVariableName(tagHelperTypeName);
+                context.Writer
+                    .Write("private global::")
+                    .WriteVariableDeclaration(
+                        tagHelperTypeName,
+                        tagHelperVariableName,
+                        value: null);
+            }
+        }
+
+        public override void WriteAddTagHelperHtmlAttribute(CSharpRenderingContext context, AddTagHelperHtmlAttributeIRNode node)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override void WriteCreateTagHelper(CSharpRenderingContext context, CreateTagHelperIRNode node)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override void WriteExecuteTagHelpers(CSharpRenderingContext context, ExecuteTagHelpersIRNode node)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override void WriteInitializeTagHelperStructure(CSharpRenderingContext context, InitializeTagHelperStructureIRNode node)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override void WriteSetTagHelperProperty(CSharpRenderingContext context, SetTagHelperPropertyIRNode node)
+        {
+            throw new NotImplementedException();
+        }
+
+        private static string GetTagHelperVariableName(string tagHelperTypeName) => "__" + tagHelperTypeName.Replace('.', '_');
+    }
+}

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

@@ -7,6 +7,8 @@ namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
 {
     public abstract class TagHelperWriter
     {
+        public abstract void WriteDeclareTagHelperFields(CSharpRenderingContext context, DeclareTagHelperFieldsIRNode node);
+
         public abstract void WriteInitializeTagHelperStructure(CSharpRenderingContext context, InitializeTagHelperStructureIRNode node);
 
         public abstract void WriteSetTagHelperProperty(CSharpRenderingContext context, SetTagHelperPropertyIRNode node);

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

@@ -0,0 +1,37 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
+{
+    public class DesignTimeTagHelperWriterTest
+    {
+        [Fact]
+        public void WriteDeclareTagHelperFields_DeclaresUsedTagHelperTypes()
+        {
+            // Arrange
+            var writer = new DesignTimeTagHelperWriter();
+            var context = new CSharpRenderingContext()
+            {
+                Writer = new Legacy.CSharpCodeWriter(),
+            };
+            var node = new DeclareTagHelperFieldsIRNode();
+            node.UsedTagHelperTypeNames.Add("PTagHelper");
+            node.UsedTagHelperTypeNames.Add("MyTagHelper");
+
+            // Act
+            writer.WriteDeclareTagHelperFields(context, node);
+
+            // Assert
+            var csharp = context.Writer.Builder.ToString();
+            Assert.Equal(
+@"private global::PTagHelper __PTagHelper = null;
+private global::MyTagHelper __MyTagHelper = null;
+",
+                csharp,
+                ignoreLineEndingDifferences: true);
+        }
+    }
+}

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

@@ -0,0 +1,95 @@
+// 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 Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Evolution.CodeGeneration
+{
+    public class RuntimeTagHelperWriterTest
+    {
+        [Fact]
+        public void WriteDeclareTagHelperFields_DeclaresRequiredFields()
+        {
+            // Arrange
+            var writer = new RuntimeTagHelperWriter();
+            var context = new CSharpRenderingContext()
+            {
+                Writer = new Legacy.CSharpCodeWriter(),
+            };
+            var node = new DeclareTagHelperFieldsIRNode();
+
+            // Act
+            writer.WriteDeclareTagHelperFields(context, node);
+
+            // Assert
+            var csharp = context.Writer.Builder.ToString();
+            Assert.Equal(
+@"#line hidden
+#pragma warning disable 0414
+private string __tagHelperStringValueBuffer = null;
+#pragma warning restore 0414
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext __tagHelperExecutionContext = null;
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner __tagHelperRunner = new global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner();
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager __backed__tagHelperScopeManager = null;
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager __tagHelperScopeManager
+{
+    get
+    {
+        if (__backed__tagHelperScopeManager == null)
+        {
+            __backed__tagHelperScopeManager = new Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager(StartTagHelperWritingScope, EndTagHelperWritingScope);
+        }
+        return __backed__tagHelperScopeManager;
+    }
+}
+",
+                csharp,
+                ignoreLineEndingDifferences: true);
+        }
+
+        [Fact]
+        public void WriteDeclareTagHelperFields_DeclaresUsedTagHelperTypes()
+        {
+            // Arrange
+            var writer = new RuntimeTagHelperWriter();
+            var context = new CSharpRenderingContext()
+            {
+                Writer = new Legacy.CSharpCodeWriter(),
+            };
+            var node = new DeclareTagHelperFieldsIRNode();
+            node.UsedTagHelperTypeNames.Add("PTagHelper");
+            node.UsedTagHelperTypeNames.Add("MyTagHelper");
+
+            // Act
+            writer.WriteDeclareTagHelperFields(context, node);
+
+            // Assert
+            var csharp = context.Writer.Builder.ToString();
+            Assert.Equal(
+@"#line hidden
+#pragma warning disable 0414
+private string __tagHelperStringValueBuffer = null;
+#pragma warning restore 0414
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext __tagHelperExecutionContext = null;
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner __tagHelperRunner = new global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner();
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager __backed__tagHelperScopeManager = null;
+private global::Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager __tagHelperScopeManager
+{
+    get
+    {
+        if (__backed__tagHelperScopeManager == null)
+        {
+            __backed__tagHelperScopeManager = new Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperScopeManager(StartTagHelperWritingScope, EndTagHelperWritingScope);
+        }
+        return __backed__tagHelperScopeManager;
+    }
+}
+private global::PTagHelper __PTagHelper = null;
+private global::MyTagHelper __MyTagHelper = null;
+",
+                csharp,
+                ignoreLineEndingDifferences: true);
+        }
+    }
+}