Adopt more of Razor Exensibility

Removes some workarounds and uses Razor extensibility in a few more
places.

_ViewImports now works in VS

src/Microsoft.AspNetCore.Blazor.Build/Core/RazorCompilation/RazorCompiler.cs

@@ -93,9 +93,9 @@ namespace Microsoft.AspNetCore.Blazor.Build.Core.RazorCompilation
                 // name and any public members. Don't need to actually emit all the RenderTreeBuilder
                 // invocations.
 
-                var engine = new BlazorRazorEngine();
+                var engine = RazorEngine.Create(b => BlazorExtensionInitializer.Register(b));
                 var blazorTemplateEngine = new BlazorTemplateEngine(
-                    engine.Engine,
+                    engine,
                     RazorProjectFileSystem.Create(inputRootPath));
                 var codeDoc = blazorTemplateEngine.CreateCodeDocument(
                     new BlazorProjectItem(inputRootPath, inputFilePath, inputFileContents));

src/Microsoft.AspNetCore.Blazor.Build/Microsoft.AspNetCore.Blazor.Build.csproj

@@ -31,6 +31,14 @@
     <None Remove="tools\**" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- This is a newer version than is in the shared framework, so copy it -->
+    <Content Include="..\Microsoft.AspNetCore.Blazor.Razor.Extensions\bin\$(Configuration)\netstandard2.0\Microsoft.AspNetCore.Razor.Language.dll">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      <Visible>false</Visible>
+    </Content>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\Microsoft.AspNetCore.Blazor.Browser.JS\Microsoft.AspNetCore.Blazor.Browser.JS.csproj" />
     <ProjectReference Include="..\Microsoft.AspNetCore.Blazor.Mono\Microsoft.AspNetCore.Blazor.Mono.csproj" />

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorApi.cs

@@ -0,0 +1,52 @@
+// 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.Blazor.Razor
+{
+    // Constants for method names used in code-generation
+    // Keep these in sync with the actual definitions
+    internal static class BlazorApi
+    {
+        public static class BlazorComponent
+        {
+            public static readonly string FullTypeName = "Microsoft.AspNetCore.Blazor.Components.BlazorComponent";
+
+            public static readonly string BuildRenderTree = nameof(BuildRenderTree);
+        }
+
+        public static class RenderFragment
+        {
+            public static readonly string FullTypeName = "Microsoft.AspNetCore.Blazor.RenderFragment";
+        }
+        
+        public static class RenderTreeBuilder
+        {
+            public static readonly string FullTypeName = "Microsoft.AspNetCore.Blazor.RenderTree.RenderTreeBuilder";
+
+            public static readonly string OpenElement = nameof(OpenElement);
+
+            public static readonly string CloseElement = nameof(CloseElement);
+
+            public static readonly string OpenComponent = nameof(OpenComponent);
+
+            public static readonly string CloseComponent = nameof(CloseElement);
+
+            public static readonly string AddContent = nameof(AddContent);
+
+            public static readonly string AddAttribute = nameof(AddAttribute);
+
+            public static readonly string Clear = nameof(Clear);
+
+            public static readonly string GetFrames = nameof(GetFrames);
+
+            public static readonly string ChildContent = nameof(ChildContent);
+        }
+
+        public static class BindMethods
+        {
+            public static readonly string GetValue = "Microsoft.AspNetCore.Blazor.Components.BindMethods.GetValue";
+
+            public static readonly string SetValue = "Microsoft.AspNetCore.Blazor.Components.BindMethods.SetValue";
+        }
+    }
+}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorCodeTarget.cs

@@ -1,7 +1,9 @@
 // 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.Linq;
+using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.CodeGeneration;
 
 namespace Microsoft.AspNetCore.Blazor.Razor
@@ -11,11 +13,47 @@ namespace Microsoft.AspNetCore.Blazor.Razor
     /// </summary>
     internal class BlazorCodeTarget : CodeTarget
     {
+        private readonly RazorCodeGenerationOptions _options;
+
+        public BlazorCodeTarget(RazorCodeGenerationOptions options, IEnumerable<ICodeTargetExtension> extensions)
+        {
+            _options = options;
+            Extensions = extensions.ToArray();
+        }
+
+        public ICodeTargetExtension[] Extensions { get; }
+
         public override IntermediateNodeWriter CreateNodeWriter()
-            => new BlazorIntermediateNodeWriter();
+        {
+            return _options.DesignTime ? (IntermediateNodeWriter)new DesignTimeNodeWriter() : new BlazorIntermediateNodeWriter();
+        }
 
-        public override TExtension GetExtension<TExtension>() => null;
+        public override TExtension GetExtension<TExtension>()
+        {
+            for (var i = 0; i < Extensions.Length; i++)
+            {
+                var match = Extensions[i] as TExtension;
+                if (match != null)
+                {
+                    return match;
+                }
+            }
 
-        public override bool HasExtension<TExtension>() => false;
+            return null;
+        }
+
+        public override bool HasExtension<TExtension>()
+        {
+            for (var i = 0; i < Extensions.Length; i++)
+            {
+                var match = Extensions[i] as TExtension;
+                if (match != null)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
     }
 }

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorComponent.cs

@@ -1,12 +0,0 @@
-// 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.Blazor.Razor
-{
-    internal static class BlazorComponent
-    {
-        public static readonly string FullTypeName = "Microsoft.AspNetCore.Blazor.Components.BlazorComponent";
-
-        public static readonly string BuildRenderTree = nameof(BuildRenderTree);
-    }
-}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorConfiguration.cs

@@ -0,0 +1,16 @@
+// 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.Language;
+
+namespace Microsoft.AspNetCore.Blazor.Razor
+{
+    public static class BlazorConfiguration 
+    {
+        public static readonly RazorConfiguration Default = new RazorConfiguration(
+            RazorLanguageVersion.Version_2_1,
+            "Blazor-0.1",
+            Array.Empty<RazorExtension>());
+    }
+}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorExtensionInitializer.cs

@@ -0,0 +1,83 @@
+// 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.Linq;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Extensions;
+
+namespace Microsoft.AspNetCore.Blazor.Razor
+{
+    public class BlazorExtensionInitializer : RazorExtensionInitializer
+    {
+        public static void Register(RazorProjectEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            FunctionsDirective.Register(builder);
+            InjectDirective.Register(builder);
+            InheritsDirective.Register(builder);
+            TemporaryLayoutPass.Register(builder);
+            TemporaryImplementsPass.Register(builder);
+
+            builder.Features.Remove(builder.Features.OfType<IImportProjectFeature>().Single());
+            builder.Features.Add(new BlazorImportProjectFeature());
+
+            builder.Features.Add(new ConfigureBlazorCodeGenerationOptions());
+
+            builder.Features.Add(new ComponentDocumentClassifierPass());
+        }
+
+        // This is temporarily used to initialize a RazorEngine by the build tools until we get the features
+        // we need into the RazorProjectEngine (namespace).
+        public static void Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            FunctionsDirective.Register(builder);
+            InjectDirective.Register(builder);
+            InheritsDirective.Register(builder);
+            TemporaryLayoutPass.Register(builder);
+            TemporaryImplementsPass.Register(builder);
+
+            builder.Features.Add(new ConfigureBlazorCodeGenerationOptions());
+
+            builder.Features.Add(new ComponentDocumentClassifierPass());
+        }
+
+        public override void Initialize(RazorProjectEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            Register(builder);
+        }
+
+        private class ConfigureBlazorCodeGenerationOptions : IConfigureRazorCodeGenerationOptionsFeature
+        {
+            public int Order => 0;
+
+            public RazorEngine Engine { get; set; }
+
+            public void Configure(RazorCodeGenerationOptionsBuilder options)
+            {
+                if (options == null)
+                {
+                    throw new ArgumentNullException(nameof(options));
+                }
+
+                // These metadata attributes require a reference to the Razor.Runtime package which we don't
+                // otherwise need.
+                options.SuppressMetadataAttributes = true;
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorImportProjectFeature.cs

@@ -0,0 +1,79 @@
+// 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;
+using System.Text;
+using Microsoft.AspNetCore.Razor.Language;
+
+namespace Microsoft.AspNetCore.Blazor.Razor
+{
+    internal class BlazorImportProjectFeature : IImportProjectFeature
+    {
+        private const string ImportsFileName = "_ViewImports.cshtml";
+
+        public RazorProjectItem DefaultImports => VirtualProjectItem.Instance;
+
+        public RazorProjectEngine ProjectEngine { get; set; }
+
+        public IReadOnlyList<RazorProjectItem> GetImports(RazorProjectItem projectItem)
+        {
+            if (projectItem == null)
+            {
+                throw new ArgumentNullException(nameof(projectItem));
+            }
+
+            var imports = new List<RazorProjectItem>()
+            {
+                VirtualProjectItem.Instance,
+            };
+
+            // We add hierarchical imports second so any default directive imports can be overridden.
+            imports.AddRange(GetHierarchicalImports(ProjectEngine.FileSystem, projectItem));
+
+            return imports;
+        }
+
+        // Temporary API until we fully convert to RazorProjectEngine
+        public IEnumerable<RazorProjectItem> GetHierarchicalImports(RazorProject project, RazorProjectItem projectItem)
+        {
+            // We want items in descending order. FindHierarchicalItems returns items in ascending order.
+            return project.FindHierarchicalItems(projectItem.FilePath, ImportsFileName).Reverse();
+        }
+
+        private class VirtualProjectItem : RazorProjectItem
+        {
+            private readonly byte[] _defaultImportBytes;
+
+            private VirtualProjectItem()
+            {
+                var preamble = Encoding.UTF8.GetPreamble();
+                var content = @"
+@using System
+@using System.Collections.Generic
+@using System.Linq
+@using System.Threading.Tasks
+";
+                var contentBytes = Encoding.UTF8.GetBytes(content);
+
+                _defaultImportBytes = new byte[preamble.Length + contentBytes.Length];
+                preamble.CopyTo(_defaultImportBytes, 0);
+                contentBytes.CopyTo(_defaultImportBytes, preamble.Length);
+            }
+
+            public override string BasePath => null;
+
+            public override string FilePath => null;
+
+            public override string PhysicalPath => null;
+
+            public override bool Exists => true;
+
+            public static VirtualProjectItem Instance { get; } = new VirtualProjectItem();
+
+            public override Stream Read() => new MemoryStream(_defaultImportBytes);
+        }
+    }
+}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorIntermediateNodeWriter.cs

@@ -126,7 +126,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
             // text to display
             _scopeStack.IncrementCurrentScopeChildCount(context);
             context.CodeWriter
-                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(RenderTreeBuilder.AddContent)}")
+                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(BlazorApi.RenderTreeBuilder.AddContent)}")
                 .Write((_sourceSequence++).ToString())
                 .WriteParameterSeparator();
 
@@ -216,7 +216,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                             // Text node
                             _scopeStack.IncrementCurrentScopeChildCount(context);
                             codeWriter
-                                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(RenderTreeBuilder.AddContent)}")
+                                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(BlazorApi.RenderTreeBuilder.AddContent)}")
                                 .Write((_sourceSequence++).ToString())
                                 .WriteParameterSeparator()
                                 .WriteStringLiteral(nextToken.Data)
@@ -237,14 +237,14 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                                 if (isComponent)
                                 {
                                     codeWriter
-                                        .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(RenderTreeBuilder.OpenComponent)}<{componentTypeName}>")
+                                        .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(BlazorApi.RenderTreeBuilder.OpenComponent)}<{componentTypeName}>")
                                         .Write((_sourceSequence++).ToString())
                                         .WriteEndMethodInvocation();
                                 }
                                 else
                                 {
                                     codeWriter
-                                        .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(RenderTreeBuilder.OpenElement)}")
+                                        .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(BlazorApi.RenderTreeBuilder.OpenElement)}")
                                         .Write((_sourceSequence++).ToString())
                                         .WriteParameterSeparator()
                                         .WriteStringLiteral(nextTag.Data)
@@ -294,8 +294,8 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                                     isComponent: isComponent,
                                     source: CalculateSourcePosition(node.Source, nextToken.Position));
                                 var closeMethodName = isComponent
-                                    ? nameof(RenderTreeBuilder.CloseComponent)
+                                    ? nameof(BlazorApi.RenderTreeBuilder.CloseComponent)
-                                    : nameof(RenderTreeBuilder.CloseElement);
+                                    : nameof(BlazorApi.RenderTreeBuilder.CloseElement);
                                 codeWriter
                                     .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{closeMethodName}")
                                     .WriteEndMethodInvocation();
@@ -334,7 +334,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                 WriteAttribute(context.CodeWriter, "value", new IntermediateToken
                 {
                     Kind = TokenKind.CSharp,
-                    Content = $"{RenderTreeBuilder.BindMethodsGetValue}({valueParams})"
+                    Content = $"{BlazorApi.BindMethods.GetValue}({valueParams})"
                 });
 
                 // [2] @onchange(BindSetValue(parsed => { X = parsed; }, X, Y, Z, ...))
@@ -350,7 +350,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                     AttributeValue = new IntermediateToken
                     {
                         Kind = TokenKind.CSharp,
-                        Content = $"onchange({RenderTreeBuilder.BindMethodsSetValue}({parsedArgsJoined}))"
+                        Content = $"onchange({BlazorApi.BindMethods.SetValue}({parsedArgsJoined}))"
                     }
                 };
                 WriteElementAttributeToken(context, tag, onChangeAttributeToken);
@@ -360,7 +360,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                 // For any other attribute token (e.g., @onclick(...)), treat it as an expression
                 // that will evaluate as an attribute frame
                 context.CodeWriter
-                    .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(RenderTreeBuilder.AddAttribute)}")
+                    .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(BlazorApi.RenderTreeBuilder.AddAttribute)}")
                     .Write((_sourceSequence++).ToString())
                     .WriteParameterSeparator()
                     .Write(token.AttributeValue.Content)
@@ -439,7 +439,7 @@ namespace Microsoft.AspNetCore.Blazor.Razor
         public void BeginWriteAttribute(CodeWriter codeWriter, string key)
         {
             codeWriter
-                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(RenderTreeBuilder.AddAttribute)}")
+                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{nameof(BlazorApi.RenderTreeBuilder.AddAttribute)}")
                 .Write((_sourceSequence++).ToString())
                 .WriteParameterSeparator()
                 .WriteStringLiteral(key)

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorLoweringPhase.cs

@@ -1,75 +0,0 @@
-// 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.Language;
-using Microsoft.AspNetCore.Razor.Language.CodeGeneration;
-using Microsoft.AspNetCore.Razor.Language.Intermediate;
-
-namespace Microsoft.AspNetCore.Blazor.Razor
-{
-    /// <summary>
-    /// A <see cref="RazorEngine"/> phase that builds the C# document corresponding to
-    /// a <see cref="RazorCodeDocument"/> for a Blazor component.
-    /// </summary>
-    internal class BlazorLoweringPhase : IRazorCSharpLoweringPhase
-    {
-        private readonly RazorCodeGenerationOptions _codegenOptions;
-
-        public BlazorLoweringPhase(RazorCodeGenerationOptions codegenOptions)
-        {
-            _codegenOptions = codegenOptions
-                ?? throw new ArgumentNullException(nameof(codegenOptions));
-        }
-
-        public RazorEngine Engine { get; set; }
-
-        public void Execute(RazorCodeDocument codeDocument)
-        {
-            var writer = BlazorComponentDocumentWriter.Create(_codegenOptions);
-            var documentNode = codeDocument.GetDocumentIntermediateNode();
-            ConvertToBlazorPrimaryMethod(documentNode);
-            var csharpDoc = writer.WriteDocument(codeDocument, documentNode);
-            codeDocument.SetCSharpDocument(csharpDoc);
-        }
-
-        private void ConvertToBlazorPrimaryMethod(DocumentIntermediateNode documentNode)
-        {
-            // Replaces the default "ExecuteAsync" method with Blazor's "BuildRenderTree".
-            // Note that DefaultDocumentWriter's VisitMethodDeclaration is hardcoded to
-            // emit methods with no parameters, so there's no way of setting the parameters
-            // from here. We inject the parameter later in RazorCompiler.
-            var primaryMethod = documentNode.FindPrimaryMethod();
-            primaryMethod.ReturnType = "void";
-            primaryMethod.MethodName = BlazorComponent.BuildRenderTree;
-            primaryMethod.Modifiers.Clear();
-            primaryMethod.Modifiers.Add("protected");
-            primaryMethod.Modifiers.Add("override");
-
-            var line = new CSharpCodeIntermediateNode();
-            line.Children.Add(new IntermediateToken
-            {
-                Kind = TokenKind.CSharp,
-                Content = $"base.{primaryMethod.MethodName}(builder);" + Environment.NewLine
-            });
-            primaryMethod.Children.Insert(0, line);
-        }
-
-        /// <summary>
-        /// Creates <see cref="DocumentWriter"/> instances that are configured to use
-        /// <see cref="BlazorCodeTarget"/>.
-        /// </summary>
-        private class BlazorComponentDocumentWriter : DocumentWriter
-        {
-            public static DocumentWriter Create(RazorCodeGenerationOptions options)
-                => Instance.Create(new BlazorCodeTarget(), options);
-
-            private static BlazorComponentDocumentWriter Instance
-                = new BlazorComponentDocumentWriter();
-
-            public override RazorCSharpDocument WriteDocument(
-                RazorCodeDocument codeDocument, DocumentIntermediateNode documentNode)
-                => throw new NotImplementedException();
-        }
-    }
-}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorRazorEngine.cs

@@ -1,46 +0,0 @@
-// 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.Linq;
-using Microsoft.AspNetCore.Razor.Language;
-using Microsoft.AspNetCore.Razor.Language.Extensions;
-
-namespace Microsoft.AspNetCore.Blazor.Razor
-{
-    /// <summary>
-    /// Wraps <see cref="RazorEngine"/>, configuring it to compile Blazor components.
-    /// </summary>
-    public class BlazorRazorEngine
-    {
-        private readonly RazorEngine _engine;
-        private readonly RazorCodeGenerationOptions _codegenOptions;
-
-        public RazorEngine Engine => _engine;
-
-        public BlazorRazorEngine()
-        {
-            _codegenOptions = RazorCodeGenerationOptions.CreateDefault();
-
-            _engine = RazorEngine.Create(configure =>
-            {
-                FunctionsDirective.Register(configure);
-                InheritsDirective.Register(configure);
-                InjectDirective.Register(configure);
-                TemporaryLayoutPass.Register(configure);
-                TemporaryImplementsPass.Register(configure);
-
-                configure.SetBaseType(BlazorComponent.FullTypeName);
-
-                configure.Phases.Remove(
-                    configure.Phases.OfType<IRazorCSharpLoweringPhase>().Single());
-                configure.Phases.Add(new BlazorLoweringPhase(_codegenOptions));
-
-                configure.ConfigureClass((codeDoc, classNode) =>
-                {
-                    configure.SetNamespace((string)codeDoc.Items[BlazorCodeDocItems.Namespace]);
-                    classNode.ClassName = (string)codeDoc.Items[BlazorCodeDocItems.ClassName];
-                });
-            });
-        }
-    }
-}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorTemplateEngine.cs

@@ -4,6 +4,7 @@
 using System.IO;
 using Microsoft.AspNetCore.Razor.Language;
 using System.Text;
+using System.Collections.Generic;
 
 namespace Microsoft.AspNetCore.Blazor.Razor
 {
@@ -12,11 +13,26 @@ namespace Microsoft.AspNetCore.Blazor.Razor
     /// </summary>
     public class BlazorTemplateEngine : RazorTemplateEngine
     {
+        // We need to implement and register this feature for tooling support to work. Subclassing TemplateEngine
+        // doesn't work inside visual studio.
+        private readonly BlazorImportProjectFeature _feature;
+
         public BlazorTemplateEngine(RazorEngine engine, RazorProject project)
             : base(engine, project)
         {
-            Options.ImportsFileName = "_ViewImports.cshtml";
+            _feature = new BlazorImportProjectFeature();
-            Options.DefaultImports = GetDefaultImports();
+            
+            Options.DefaultImports = RazorSourceDocument.ReadFrom(_feature.DefaultImports);
+        }
+
+        public override IEnumerable<RazorProjectItem> GetImportItems(RazorProjectItem projectItem)
+        {
+            if (projectItem == null)
+            {
+                throw new System.ArgumentNullException(nameof(projectItem));
+            }
+
+            return _feature.GetHierarchicalImports(Project, projectItem);
         }
 
         private static RazorSourceDocument GetDefaultImports()

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/ComponentDocumentClassifierPass.cs

@@ -0,0 +1,94 @@
+// 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.Language;
+using Microsoft.AspNetCore.Razor.Language.CodeGeneration;
+using Microsoft.AspNetCore.Razor.Language.Intermediate;
+using System;
+using System.IO;
+using System.Linq;
+
+namespace Microsoft.AspNetCore.Blazor.Razor
+{
+    internal class ComponentDocumentClassifierPass : DocumentClassifierPassBase, IRazorDocumentClassifierPass
+    {
+        protected override string DocumentKind => "Blazor.Component-0.1";
+
+        protected override bool IsMatch(RazorCodeDocument codeDocument, DocumentIntermediateNode documentNode)
+        {
+            // Treat everything as a component by default if Blazor is part of the configuration.
+            return true;
+        }
+
+        protected override void OnDocumentStructureCreated(
+            RazorCodeDocument codeDocument, 
+            NamespaceDeclarationIntermediateNode @namespace, 
+            ClassDeclarationIntermediateNode @class, 
+            MethodDeclarationIntermediateNode method)
+        {
+            @namespace.Content = (string)codeDocument.Items[BlazorCodeDocItems.Namespace];
+            if (@namespace.Content == null)
+            {
+                @namespace.Content = "Blazor";
+            }
+
+            @class.BaseType = BlazorApi.BlazorComponent.FullTypeName;
+            @class.ClassName = (string)codeDocument.Items[BlazorCodeDocItems.ClassName];
+            if (@class.ClassName == null)
+            {
+                @class.ClassName = codeDocument.Source.FilePath == null ? null : Path.GetFileNameWithoutExtension(codeDocument.Source.FilePath);
+            }
+
+            if (@class.ClassName == null)
+            {
+                @class.ClassName = "__BlazorComponent";
+            }
+
+            @class.Modifiers.Clear();
+            @class.Modifiers.Add("public");
+
+            method.ReturnType = "void";
+            method.MethodName = BlazorApi.BlazorComponent.BuildRenderTree;
+            method.Modifiers.Clear();
+            method.Modifiers.Add("protected");
+            method.Modifiers.Add("override");
+
+            method.Parameters.Clear();
+            method.Parameters.Add(new MethodParameter()
+            {
+                ParameterName = "builder",
+                TypeName = BlazorApi.RenderTreeBuilder.FullTypeName,
+            });
+
+            // We need to call the 'base' method as the first statement.
+            var callBase = new CSharpCodeIntermediateNode();
+            callBase.Children.Add(new IntermediateToken
+            {
+                Kind = TokenKind.CSharp,
+                Content = $"base.{BlazorApi.BlazorComponent.BuildRenderTree}(builder);" + Environment.NewLine
+            });
+            method.Children.Insert(0, callBase);
+        }
+
+        #region Workaround
+        // This is a workaround for the fact that the base class doesn't provide good support
+        // for replacing the IntermediateNodeWriter when building the code target. 
+        void IRazorDocumentClassifierPass.Execute(RazorCodeDocument codeDocument, DocumentIntermediateNode documentNode)
+        {
+            base.Execute(codeDocument, documentNode);
+            documentNode.Target = new BlazorCodeTarget(documentNode.Options, _targetExtensions);
+        }
+
+        protected override void OnInitialized()
+        {
+            base.OnInitialized();
+
+            var feature = Engine.Features.OfType<IRazorTargetExtensionFeature>();
+            _targetExtensions = feature.FirstOrDefault()?.TargetExtensions.ToArray() ?? EmptyExtensionArray;
+        }
+
+        private static readonly ICodeTargetExtension[] EmptyExtensionArray = new ICodeTargetExtension[0];
+        private ICodeTargetExtension[] _targetExtensions;
+        #endregion
+    }
+}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/InjectDirective.cs

@@ -29,6 +29,12 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                 builder.Description = "Inject a service from the application's service container into a property.";
             });
 
+        public static void Register(RazorProjectEngineBuilder builder)
+        {
+            builder.AddDirective(Directive);
+            builder.Features.Add(new Pass());
+        }
+
         public static void Register(IRazorEngineBuilder builder)
         {
             builder.AddDirective(Directive);

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/Microsoft.AspNetCore.Blazor.Razor.Extensions.csproj

@@ -4,6 +4,9 @@
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <TargetFrameworks Condition="'$(OS)' == 'Windows_NT'">$(TargetFrameworks);net461</TargetFrameworks>
     <RootNamespace>Microsoft.AspNetCore.Blazor.Razor</RootNamespace>
+    
+    <!-- Copy package references to output, needed so the build project can find them -->
+    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
   </PropertyGroup>
 
   <ItemGroup>

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/Properties/AssemblyInfo.cs

@@ -0,0 +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 Microsoft.AspNetCore.Blazor.Razor;
+using Microsoft.AspNetCore.Razor.Language;
+
+[assembly: ProvideRazorExtensionInitializer("Blazor-0.1", typeof(BlazorExtensionInitializer))]

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/RenderTreeBuilder.cs

@@ -1,32 +0,0 @@
-// 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.Blazor.Razor
-{
-    // Constants for method names used in code-generation
-    // Keep these in sync with the actual RenderTreeBuilder definitions
-    internal static class RenderTreeBuilder
-    {
-        public static readonly string OpenElement = nameof(OpenElement);
-
-        public static readonly string CloseElement = nameof(CloseElement);
-
-        public static readonly string OpenComponent = nameof(OpenComponent);
-
-        public static readonly string CloseComponent = nameof(CloseElement);
-
-        public static readonly string AddContent = nameof(AddContent);
-
-        public static readonly string AddAttribute = nameof(AddAttribute);
-        
-        public static readonly string Clear = nameof(Clear);
-
-        public static readonly string GetFrames = nameof(GetFrames);
-
-        public static readonly string ChildContent = nameof(ChildContent);
-
-        public static readonly string BindMethodsGetValue = "Microsoft.AspNetCore.Blazor.Components.BindMethods.GetValue";
-
-        public static readonly string BindMethodsSetValue = "Microsoft.AspNetCore.Blazor.Components.BindMethods.SetValue";
-    }
-}

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/ScopeStack.cs

@@ -15,8 +15,6 @@ namespace Microsoft.AspNetCore.Blazor.Razor
     /// </summary>
     internal class ScopeStack
     {
-        private const string _renderFragmentTypeName = "Microsoft.AspNetCore.Blazor.RenderFragment";
-
         private readonly Stack<ScopeEntry> _stack = new Stack<ScopeEntry>();
         private int _builderVarNumber = 1;
 
@@ -72,9 +70,9 @@ namespace Microsoft.AspNetCore.Blazor.Razor
                     // When we're about to insert the first child into a component,
                     // it's time to open a new lambda
                     var blazorNodeWriter = (BlazorIntermediateNodeWriter)context.NodeWriter;
-                    blazorNodeWriter.BeginWriteAttribute(context.CodeWriter, RenderTreeBuilder.ChildContent);
+                    blazorNodeWriter.BeginWriteAttribute(context.CodeWriter, BlazorApi.RenderTreeBuilder.ChildContent);
                     OffsetBuilderVarNumber(1);
-                    context.CodeWriter.Write($"({_renderFragmentTypeName})(");
+                    context.CodeWriter.Write($"({BlazorApi.RenderFragment.FullTypeName})(");
                     currentScope.LambdaScope = context.CodeWriter.BuildLambda(BuilderVarName);
                 }
 

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/Temporary/TemporaryImplementsPass.cs

@@ -22,9 +22,14 @@ namespace Microsoft.AspNetCore.Blazor.Razor
         // Captures: MyApp.Namespace.ISomeType<T1, T2>
         private const string ImplementsTokenPattern = @"\s*Implements\s*<(.+)\>\s*\(\s*\)\s*";
 
-        public static void Register(IRazorEngineBuilder configuration)
+        public static void Register(IRazorEngineBuilder builder)
         {
-            configuration.Features.Add(new TemporaryImplementsPass());
+            builder.Features.Add(new TemporaryImplementsPass());
+        }
+
+        public static void Register(RazorProjectEngineBuilder builder)
+        {
+            builder.Features.Add(new TemporaryImplementsPass());
         }
 
         private TemporaryImplementsPass() : base(ImplementsTokenPattern)

src/Microsoft.AspNetCore.Blazor.Razor.Extensions/Temporary/TemporaryLayoutPass.cs

@@ -25,9 +25,14 @@ namespace Microsoft.AspNetCore.Blazor.Razor
         private const string LayoutAttributeTypeName
             = "Microsoft.AspNetCore.Blazor.Layouts.LayoutAttribute";
 
-        public static void Register(IRazorEngineBuilder configuration)
+        public static void Register(IRazorEngineBuilder builder)
         {
-            configuration.Features.Add(new TemporaryLayoutPass());
+            builder.Features.Add(new TemporaryLayoutPass());
+        }
+
+        public static void Register(RazorProjectEngineBuilder builder)
+        {
+            builder.Features.Add(new TemporaryLayoutPass());
         }
 
         private TemporaryLayoutPass() : base(LayoutTokenPattern)

src/Microsoft.AspNetCore.Blazor/Components/BlazorComponent.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNetCore.Blazor.Components
     // IMPORTANT
     //
     // Many of these names are used in code generation. Keep these in sync with the code generation code
-    // See: src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorComponent.cs
+    // See: src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorApi.cs
 
     // Most of the developer-facing component lifecycle concepts are encapsulated in this
     // base class. The core Blazor rendering system doesn't know about them (it only knows

src/Microsoft.AspNetCore.Blazor/RenderTree/RenderTreeBuilder.cs

@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.Blazor.RenderTree
     // IMPORTANT
     //
     // Many of these names are used in code generation. Keep these in sync with the code generation code
-    // See: src/Microsoft.AspNetCore.Blazor.Razor.Extensions/RenderTreeBuilder.cs
+    // See: src/Microsoft.AspNetCore.Blazor.Razor.Extensions/BlazorApi.cs
 
     /// <summary>
     /// Provides methods for building a collection of <see cref="RenderTreeFrame"/> entries.

tooling/Microsoft.VisualStudio.LanguageServices.Blazor/BlazorProjectEngineFactory.cs

@@ -0,0 +1,23 @@
+// 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.Blazor.Razor;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Razor;
+
+namespace Microsoft.VisualStudio.LanguageServices.Blazor
+{
+    [ExportCustomProjectEngineFactory("Blazor-0.1", SupportsSerialization = false)]
+    internal class BlazorProjectEngineFactory : IProjectEngineFactory
+    {
+        public RazorProjectEngine Create(RazorConfiguration configuration, RazorProjectFileSystem fileSystem, Action<RazorProjectEngineBuilder> configure)
+        {
+            return RazorProjectEngine.Create(configuration, fileSystem, b =>
+            {
+                configure?.Invoke(b);
+                new BlazorExtensionInitializer().Initialize(b);
+            });
+        }
+    }
+}