Add support for type parameters to class nodes

This change will allow someone extending Razor to use generic type
parameters in generated classes.

There's no user-level extensibility provided here yet, as in there is no
language support for adding type parameters.

src/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/ViewComponentTagHelperTargetExtension.cs

@@ -60,7 +60,12 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
             WriteTargetElementString(context.CodeWriter, node.TagHelper);
 
             // Initialize declaration.
-            using (context.CodeWriter.BuildClassDeclaration(PublicModifiers, node.ClassName, TagHelperTypeName, interfaces: null))
+            using (context.CodeWriter.BuildClassDeclaration(
+                PublicModifiers,
+                node.ClassName,
+                TagHelperTypeName,
+                interfaces: null,
+                typeParameters: null))
             {
                 // Add view component helper.
                 context.CodeWriter.WriteVariableDeclaration(

src/Microsoft.AspNetCore.Mvc.Razor.Extensions/ViewComponentTagHelperTargetExtension.cs

@@ -60,7 +60,12 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
             WriteTargetElementString(context.CodeWriter, node.TagHelper);
 
             // Initialize declaration.
-            using (context.CodeWriter.BuildClassDeclaration(PublicModifiers, node.ClassName, TagHelperTypeName, interfaces: null))
+            using (context.CodeWriter.BuildClassDeclaration(
+                PublicModifiers,
+                node.ClassName,
+                TagHelperTypeName,
+                interfaces: null,
+                typeParameters: null))
             {
                 // Add view component helper.
                 context.CodeWriter.WriteVariableDeclaration(

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

@@ -374,7 +374,8 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
             IList<string> modifiers,
             string name,
             string baseType,
-            IEnumerable<string> interfaces)
+            IList<string> interfaces,
+            IList<string> typeParameters)
         {
             for (var i = 0; i < modifiers.Count; i++)
             {
@@ -385,8 +386,15 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
             writer.Write("class ");
             writer.Write(name);
 
+            if (typeParameters != null && typeParameters.Count > 0)
+            {
+                writer.Write("<");
+                writer.Write(string.Join(", ", typeParameters));
+                writer.Write(">");
+            }
+
             var hasBaseType = !string.IsNullOrEmpty(baseType);
-            var hasInterfaces = interfaces != null && interfaces.Count() > 0;
+            var hasInterfaces = interfaces != null && interfaces.Count > 0;
 
             if (hasBaseType || hasInterfaces)
             {

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

@@ -78,8 +78,8 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
                     {
                         algorithmId = "{8829d00f-11b8-4213-878b-770e8597ac16}";
                     }
-                    else if (string.Equals(algorithm, HashAlgorithmName.SHA1.Name, StringComparison.Ordinal) || 
-                        
+                    else if (string.Equals(algorithm, HashAlgorithmName.SHA1.Name, StringComparison.Ordinal) ||
+
                         // In 2.0, we didn't actually expose the name of the algorithm, so it's possible we could get null here.
                         // If that's the case, we just assume SHA1 since that's the only thing we supported in 2.0.
                         algorithm == null)
@@ -88,7 +88,7 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
                     }
                     else
                     {
-                        var supportedAlgorithms = string.Join(" ", new string[] 
+                        var supportedAlgorithms = string.Join(" ", new string[]
                         {
                             HashAlgorithmName.SHA1.Name,
                             HashAlgorithmName.SHA256.Name
@@ -143,7 +143,12 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
 
             public override void VisitClassDeclaration(ClassDeclarationIntermediateNode node)
             {
-                using (Context.CodeWriter.BuildClassDeclaration(node.Modifiers, node.ClassName, node.BaseType, node.Interfaces))
+                using (Context.CodeWriter.BuildClassDeclaration(
+                    node.Modifiers,
+                    node.ClassName,
+                    node.BaseType,
+                    node.Interfaces,
+                    node.TypeParameters.Select(p => p.ParameterName).ToArray()))
                 {
                     VisitDefault(node);
                 }

src/Microsoft.AspNetCore.Razor.Language/Intermediate/ClassDeclarationIntermediateNode.cs

@@ -16,7 +16,9 @@ namespace Microsoft.AspNetCore.Razor.Language.Intermediate
 
         public string BaseType { get; set; }
 
-        public IList<string> Interfaces { get; set; }
+        public IList<string> Interfaces { get; set; } = new List<string>();
+
+        public IList<TypeParameter> TypeParameters { get; set; } = new List<TypeParameter>();
 
         public override void Accept(IntermediateNodeVisitor visitor)
         {

src/Microsoft.AspNetCore.Razor.Language/Intermediate/TypeParameter.cs

@@ -0,0 +1,10 @@
+// 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.Intermediate
+{
+    public sealed class TypeParameter
+    {
+        public string ParameterName { get; set; }
+    }
+}

test/Microsoft.AspNetCore.Razor.Language.Test/CodeGeneration/DefaultDocumentWriterTest.cs

@@ -218,6 +218,11 @@ namespace TestNamespace
                 },
                 BaseType = "TestBase",
                 Interfaces = new List<string> { "IFoo", "IBar", },
+                TypeParameters = new List<TypeParameter>
+                {
+                    new TypeParameter() { ParameterName = "TKey", },
+                    new TypeParameter() { ParameterName = "TValue", },
+                },
                 ClassName = "TestClass",
             });
 
@@ -236,7 +241,7 @@ namespace TestNamespace
 @"#pragma checksum ""test.cshtml"" ""{ff1816ec-aa5e-4d10-87f7-6f4963833460}"" ""da39a3ee5e6b4b0d3255bfef95601890afd80709""
 // <auto-generated/>
 #pragma warning disable 1591
-internal class TestClass : TestBase, IFoo, IBar
+internal class TestClass<TKey, TValue> : TestBase, IFoo, IBar
 {
 }
 #pragma warning restore 1591

test/Microsoft.AspNetCore.Razor.Language.Test/IntegrationTests/RazorTemplateEngineIntegrationTest.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.IO;
+using Microsoft.AspNetCore.Razor.Language.Intermediate;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
@@ -66,6 +67,7 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
 
                 engine.ConfigureClass((document, @class) =>
                 {
+                    @class.TypeParameters = new[] { new TypeParameter() { ParameterName = "TValue", }, };
                     @class.Interfaces = new[] { "global::System.IDisposable" };
                     @class.BaseType = "CustomBaseType";
                 });

test/Microsoft.AspNetCore.Razor.Language.Test/TestFiles/IntegrationTests/RazorTemplateEngineIntegrationTest/GenerateCodeWithConfigureClass.codegen.cs

@@ -5,7 +5,7 @@ namespace Razor
 {
     #line hidden
     [global::Microsoft.AspNetCore.Razor.Hosting.RazorSourceChecksumAttribute(@"SHA1", @"38aa8e26c5d2a85c61d8e93fe69dd326fe82671b", @"/TestFiles/IntegrationTests/RazorTemplateEngineIntegrationTest/GenerateCodeWithConfigureClass.cshtml")]
-    protected internal class MyClass : CustomBaseType, global::System.IDisposable
+    protected internal class MyClass<TValue> : CustomBaseType, global::System.IDisposable
     {
         #pragma warning disable 1998
         public async override global::System.Threading.Tasks.Task ExecuteAsync()

test/Microsoft.AspNetCore.Razor.Test.Common/Language/IntegrationTests/IntermediateNodeWriter.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -12,7 +13,7 @@ using Microsoft.AspNetCore.Razor.Language.Intermediate;
 namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
 {
     // Serializes single IR nodes (shallow).
-    public class IntermediateNodeWriter : 
+    public class IntermediateNodeWriter :
         IntermediateNodeVisitor,
         IExtensionIntermediateNodeVisitor<SectionIntermediateNode>
     {
@@ -32,7 +33,21 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
 
         public override void VisitClassDeclaration(ClassDeclarationIntermediateNode node)
         {
-            WriteContentNode(node, string.Join(" ", node.Modifiers), node.ClassName, node.BaseType, string.Join(", ", node.Interfaces ?? new List<string>()));
+            var entries = new List<string>()
+            {
+                string.Join(" ", node.Modifiers),
+                node.ClassName,
+                node.BaseType,
+                string.Join(", ", node.Interfaces ?? Array.Empty<string>())
+            };
+
+            // Avoid adding the type parameters to the baseline if they aren't present.
+            if (node.TypeParameters != null && node.TypeParameters.Count > 0)
+            {
+                entries.Add(string.Join(", ", node.TypeParameters));
+            }
+
+            WriteContentNode(node, entries.ToArray());
         }
 
         public override void VisitCSharpExpressionAttributeValue(CSharpExpressionAttributeValueIntermediateNode node)