Move to RazorProjectEngine.

- Instead of using Razor/Mvc TemplateEngine use `RazorProjectEngine`. This involved changing several locations (each of which used `RazorTemplateEngine` in an entirely different way) to use the RazorProjectEngine's two Process methods.
- Changed an unused public API `VisualStudioRazorParser.TemplateEngine` to `VisualStudioRazorParser.RazorProjectEngine`.
- Ported the remainder of `RazorEngineBuilder`'s extension methods over to `RazorProjectEngineBuilder`. These were used in tests and our `RazorGenerate` tool.
- Added a few test helper methods/classes to enable simple testing of the `RazorProjectEngine`.
- Resolved several test hacks that were working around little discrepancies each of the `RazorTemplateEngine` APIs.
- Changed the template engine factory service to be a project engine factory service.

benchmarks/Microsoft.AspNetCore.Razor.Performance/CodeGenerationBenchmark.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.Collections.Generic;
 using System.IO;
 using BenchmarkDotNet.Attributes;
 using Microsoft.AspNetCore.Mvc.Razor.Extensions;
@@ -21,33 +20,22 @@ namespace Microsoft.AspNetCore.Razor.Performance
             }
 
             var root = current;
-
-            var engine = RazorEngine.Create(b => { RazorExtensions.Register(b); });
-
             var fileSystem = RazorProjectFileSystem.Create(root.FullName);
+            
+            ProjectEngine = RazorProjectEngine.Create(RazorConfiguration.Default, fileSystem, b => RazorExtensions.Register(b)); ;
 
-            DesignTimeTemplateEngine = new MvcRazorTemplateEngine(RazorEngine.CreateDesignTime(b => { RazorExtensions.Register(b); }), fileSystem);
+            MSN = fileSystem.GetItem(Path.Combine(root.FullName, "MSN.cshtml"));
-            RuntimeTemplateEngine = new MvcRazorTemplateEngine(RazorEngine.Create(b => { RazorExtensions.Register(b); }), fileSystem);
-
-            var codeDocument = RuntimeTemplateEngine.CreateCodeDocument(Path.Combine(root.FullName, "MSN.cshtml"));
-
-            Imports = codeDocument.Imports;
-            MSN = codeDocument.Source;
         }
 
-        public RazorTemplateEngine DesignTimeTemplateEngine { get; }
+        public RazorProjectEngine ProjectEngine { get; }
 
-        public RazorTemplateEngine RuntimeTemplateEngine { get; }
+        public RazorProjectItem MSN { get; }
-
-        public IReadOnlyList<RazorSourceDocument> Imports { get; }
-
-        public RazorSourceDocument MSN { get; }
 
         [Benchmark(Description = "Razor Design Time Code Generation of MSN.com")]
         public void CodeGeneration_DesignTime_LargeStaticFile()
         {
-            var codeDocument = RazorCodeDocument.Create(MSN, Imports);
+            var codeDocument = ProjectEngine.ProcessDesignTime(MSN);
-            var generated = DesignTimeTemplateEngine.GenerateCode(codeDocument);
+            var generated = codeDocument.GetCSharpDocument();
 
             if (generated.Diagnostics.Count != 0)
             {
@@ -58,8 +46,8 @@ namespace Microsoft.AspNetCore.Razor.Performance
         [Benchmark(Description = "Razor Runtime Code Generation of MSN.com")]
         public void CodeGeneration_Runtime_LargeStaticFile()
         {
-            var codeDocument = RazorCodeDocument.Create(MSN, Imports);
+            var codeDocument = ProjectEngine.Process(MSN);
-            var generated = RuntimeTemplateEngine.GenerateCode(codeDocument);
+            var generated = codeDocument.GetCSharpDocument();
 
             if (generated.Diagnostics.Count != 0)
             {

src/Microsoft.AspNetCore.Razor.Language/Properties/AssemblyInfo.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.Runtime.CompilerServices;
+[assembly: InternalsVisibleTo("Microsoft.AspNetCore.Razor.Performance, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Mvc.Razor.Extensions.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Razor.GenerateTool, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

src/Microsoft.AspNetCore.Razor.Language/RazorProjectEngineBuilderExtensions.cs

@@ -2,13 +2,77 @@
 // 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.CodeGeneration;
+using Microsoft.AspNetCore.Razor.Language.Intermediate;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
     public static class RazorProjectEngineBuilderExtensions
     {
+        /// <summary>
+        /// Registers a class configuration delegate that gets invoked during code generation.
+        /// </summary>
+        /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
+        /// <param name="configureClass"><see cref="Action"/> invoked to configure 
+        /// <see cref="ClassDeclarationIntermediateNode"/> during code generation.</param>
+        /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
+        public static RazorProjectEngineBuilder ConfigureClass(
+            this RazorProjectEngineBuilder builder,
+            Action<RazorCodeDocument, ClassDeclarationIntermediateNode> configureClass)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (configureClass == null)
+            {
+                throw new ArgumentNullException(nameof(configureClass));
+            }
+
+            var configurationFeature = GetDefaultDocumentClassifierPassFeature(builder);
+            configurationFeature.ConfigureClass.Add(configureClass);
+            return builder;
+        }
+
+        /// <summary>
+        /// Sets the base type for generated types.
+        /// </summary>
+        /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
+        /// <param name="baseType">The name of the base type.</param>
+        /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
+        public static RazorProjectEngineBuilder SetBaseType(this RazorProjectEngineBuilder builder, string baseType)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            var configurationFeature = GetDefaultDocumentClassifierPassFeature(builder);
+            configurationFeature.ConfigureClass.Add((document, @class) => @class.BaseType = baseType);
+            return builder;
+        }
+
+        /// <summary>
+        /// Sets the namespace for generated types.
+        /// </summary>
+        /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
+        /// <param name="namespaceName">The name of the namespace.</param>
+        /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
+        public static RazorProjectEngineBuilder SetNamespace(this RazorProjectEngineBuilder builder, string namespaceName)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            var configurationFeature = GetDefaultDocumentClassifierPassFeature(builder);
+            configurationFeature.ConfigureNamespace.Add((document, @namespace) => @namespace.Content = namespaceName);
+            return builder;
+        }
+
         public static void SetImportFeature(this RazorProjectEngineBuilder builder, IImportProjectFeature feature)
         {
             if (builder == null)
@@ -79,6 +143,27 @@ namespace Microsoft.AspNetCore.Razor.Language
             return builder;
         }
 
+        /// <summary>
+        /// Adds the provided <see cref="RazorSourceDocument" /> documents as imports to all documents processed
+        /// by the <see cref="RazorProjectEngine"/>.
+        /// </summary>
+        /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
+        /// <param name="imports">The collection of imports.</param>
+        /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
+        public static RazorProjectEngineBuilder AddDefaultImports(this RazorProjectEngineBuilder builder, params RazorSourceDocument[] imports)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            var existingImportFeature = builder.Features.OfType<IImportProjectFeature>().First();
+            var testImportFeature = new AdditionalImportsProjectFeature(existingImportFeature, imports);
+            builder.SetImportFeature(testImportFeature);
+
+            return builder;
+        }
+
         private static IRazorDirectiveFeature GetDirectiveFeature(RazorProjectEngineBuilder builder)
         {
             var directiveFeature = builder.Features.OfType<IRazorDirectiveFeature>().FirstOrDefault();
@@ -102,5 +187,47 @@ namespace Microsoft.AspNetCore.Razor.Language
 
             return targetExtensionFeature;
         }
+
+        private static DefaultDocumentClassifierPassFeature GetDefaultDocumentClassifierPassFeature(RazorProjectEngineBuilder builder)
+        {
+            var configurationFeature = builder.Features.OfType<DefaultDocumentClassifierPassFeature>().FirstOrDefault();
+            if (configurationFeature == null)
+            {
+                configurationFeature = new DefaultDocumentClassifierPassFeature();
+                builder.Features.Add(configurationFeature);
+            }
+
+            return configurationFeature;
+        }
+
+        private class AdditionalImportsProjectFeature : RazorProjectEngineFeatureBase, IImportProjectFeature
+        {
+            private readonly IImportProjectFeature _existingImportFeature;
+            private readonly RazorSourceDocument[] _imports;
+
+            public override RazorProjectEngine ProjectEngine
+            {
+                get => base.ProjectEngine;
+                set
+                {
+                    _existingImportFeature.ProjectEngine = value;
+                    base.ProjectEngine = value;
+                }
+            }
+
+            public AdditionalImportsProjectFeature(IImportProjectFeature existingImportFeature, params RazorSourceDocument[] imports)
+            {
+                _existingImportFeature = existingImportFeature;
+                _imports = imports;
+            }
+
+            public IReadOnlyList<RazorSourceDocument> GetImports(RazorProjectItem projectItem)
+            {
+                var imports = _existingImportFeature.GetImports(projectItem).ToList();
+                imports.AddRange(_imports);
+
+                return imports;
+            }
+        }
     }
 }

src/Microsoft.AspNetCore.Razor.Tools/CompositeRazorProjectFileSystem.cs

@@ -3,24 +3,25 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 
 namespace Microsoft.AspNetCore.Razor.Tools
 {
     internal class CompositeRazorProjectFileSystem : RazorProjectFileSystem
     {
-        public CompositeRazorProjectFileSystem(IReadOnlyList<RazorProjectFileSystem> projects)
+        public CompositeRazorProjectFileSystem(IReadOnlyList<RazorProjectFileSystem> fileSystems)
         {
-            Projects = projects ?? throw new ArgumentNullException(nameof(projects));
+            FileSystems = fileSystems ?? throw new ArgumentNullException(nameof(fileSystems));
         }
 
-        public IReadOnlyList<RazorProjectFileSystem> Projects { get; }
+        public IReadOnlyList<RazorProjectFileSystem> FileSystems { get; }
 
         public override IEnumerable<RazorProjectItem> EnumerateItems(string basePath)
         {
-            foreach (var project in Projects)
+            foreach (var fileSystem in FileSystems)
             {
-                foreach (var result in project.EnumerateItems(basePath))
+                foreach (var result in fileSystem.EnumerateItems(basePath))
                 {
                     yield return result;
                 }
@@ -30,9 +31,9 @@ namespace Microsoft.AspNetCore.Razor.Tools
         public override RazorProjectItem GetItem(string path)
         {
             RazorProjectItem razorProjectItem = null;
-            foreach (var project in Projects)
+            foreach (var fileSystem in FileSystems)
             {
-                razorProjectItem = project.GetItem(path);
+                razorProjectItem = fileSystem.GetItem(path);
                 if (razorProjectItem != null && razorProjectItem.Exists)
                 {
                     return razorProjectItem;

src/Microsoft.AspNetCore.Razor.Tools/GenerateCommand.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc.Razor.Extensions;
@@ -90,26 +91,20 @@ namespace Microsoft.AspNetCore.Razor.Tools
             tagHelperManifest = Path.Combine(projectDirectory, tagHelperManifest);
 
             var tagHelpers = GetTagHelpers(tagHelperManifest);
-
+            var inputItems = GetInputItems(projectDirectory, sources, outputs, relativePaths);
-            var engine = RazorEngine.Create(b =>
+            var compositeFileSystem = new CompositeRazorProjectFileSystem(new[]
+            {
+                GetVirtualRazorProjectSystem(inputItems),
+                RazorProjectFileSystem.Create(projectDirectory),
+            });
+            var projectEngine = RazorProjectEngine.Create(RazorConfiguration.Default, compositeFileSystem, b =>
             {
                 RazorExtensions.Register(b);
 
                 b.Features.Add(new StaticTagHelperFeature() { TagHelpers = tagHelpers, });
             });
 
-
+            var results = GenerateCode(projectEngine, inputItems);
-            var inputItems = GetInputItems(projectDirectory, sources, outputs, relativePaths);
-            var compositeProject = new CompositeRazorProjectFileSystem(
-                new[]
-                {
-                    GetVirtualRazorProjectSystem(inputItems),
-                    RazorProjectFileSystem.Create(projectDirectory),
-                });
-
-            var templateEngine = new MvcRazorTemplateEngine(engine, compositeProject);
-
-            var results = GenerateCode(templateEngine, inputItems);
 
             var success = true;
 
@@ -180,14 +175,15 @@ namespace Microsoft.AspNetCore.Razor.Tools
             return items;
         }
 
-        private OutputItem[] GenerateCode(RazorTemplateEngine templateEngine, SourceItem[] inputs)
+        private OutputItem[] GenerateCode(RazorProjectEngine projectEngine, SourceItem[] inputs)
         {
             var outputs = new OutputItem[inputs.Length];
-            Parallel.For(0, outputs.Length, new ParallelOptions() { MaxDegreeOfParallelism = 4 }, i =>
+            Parallel.For(0, outputs.Length, new ParallelOptions() { MaxDegreeOfParallelism = Debugger.IsAttached ? 1 : 4 }, i =>
             {
                 var inputItem = inputs[i];
-
+                var projectItem = projectEngine.FileSystem.GetItem(inputItem.FilePath);
-                var csharpDocument = templateEngine.GenerateCode(inputItem.FilePath);
+                var codeDocument = projectEngine.Process(projectItem);
+                var csharpDocument = codeDocument.GetCSharpDocument();
                 outputs[i] = new OutputItem(inputItem, csharpDocument);
             });
 

src/Microsoft.CodeAnalysis.Razor.Workspaces/RazorProjectEngineFactoryService.cs

@@ -7,8 +7,8 @@ using Microsoft.CodeAnalysis.Host;
 
 namespace Microsoft.CodeAnalysis.Razor
 {
-    internal abstract class RazorTemplateEngineFactoryService : ILanguageService
+    internal abstract class RazorProjectEngineFactoryService : ILanguageService
     {
-        public abstract RazorTemplateEngine Create(string projectPath, Action<IRazorEngineBuilder> configure);
+        public abstract RazorProjectEngine Create(string projectPath, Action<RazorProjectEngineBuilder> configure);
     }
 }

src/Microsoft.VisualStudio.Editor.Razor/BackgroundParser.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Text;
 using System.Threading;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
@@ -18,10 +19,10 @@ namespace Microsoft.VisualStudio.Editor.Razor
         private MainThreadState _main;
         private BackgroundThread _bg;
 
-        public BackgroundParser(RazorTemplateEngine templateEngine, string filePath)
+        public BackgroundParser(RazorProjectEngine projectEngine, string filePath, string projectDirectory)
         {
             _main = new MainThreadState(filePath);
-            _bg = new BackgroundThread(_main, templateEngine, filePath);
+            _bg = new BackgroundThread(_main, projectEngine, filePath, projectDirectory);
 
             _main.ResultsReady += (sender, args) => OnResultsReady(args);
         }
@@ -233,22 +234,25 @@ namespace Microsoft.VisualStudio.Editor.Razor
 
         private class BackgroundThread : ThreadStateBase
         {
+            private readonly string _filePath;
+            private readonly string _relativeFilePath;
+            private readonly string _projectDirectory;
             private MainThreadState _main;
             private Thread _backgroundThread;
             private CancellationToken _shutdownToken;
-            private RazorTemplateEngine _templateEngine;
+            private RazorProjectEngine _projectEngine;
-            private string _filePath;
             private RazorSyntaxTree _currentSyntaxTree;
             private IList<Edit> _previouslyDiscarded = new List<Edit>();
 
-            public BackgroundThread(MainThreadState main, RazorTemplateEngine templateEngine, string fileName)
+            public BackgroundThread(MainThreadState main, RazorProjectEngine projectEngine, string filePath, string projectDirectory)
             {
                 // Run on MAIN thread!
                 _main = main;
                 _shutdownToken = _main.CancelToken;
-                _templateEngine = templateEngine;
+                _projectEngine = projectEngine;
-                _filePath = fileName;
+                _filePath = filePath;
-
+                _relativeFilePath = GetNormalizedRelativeFilePath(filePath, projectDirectory);
+                _projectDirectory = projectDirectory;
                 _backgroundThread = new Thread(WorkerLoop);
                 SetThreadId(_backgroundThread.ManagedThreadId);
             }
@@ -262,8 +266,6 @@ namespace Microsoft.VisualStudio.Editor.Razor
             // **** BACKGROUND THREAD ****
             private void WorkerLoop()
             {
-                var fileNameOnly = Path.GetFileName(_filePath);
-
                 try
                 {
                     EnsureOnThread();
@@ -347,14 +349,31 @@ namespace Microsoft.VisualStudio.Editor.Razor
             {
                 EnsureOnThread();
 
-                var sourceDocument = new TextSnapshotSourceDocument(snapshot, _filePath);
+                var projectItem = new TextSnapshotProjectItem(snapshot, _projectDirectory, _relativeFilePath, _filePath);
-                var imports = _templateEngine.GetImports(_filePath);
+                var codeDocument = _projectEngine.ProcessDesignTime(projectItem);
 
-                var codeDocument = RazorCodeDocument.Create(sourceDocument, imports);
-
-                _templateEngine.GenerateCode(codeDocument);
                 return codeDocument;
             }
+
+            private string GetNormalizedRelativeFilePath(string filePath, string projectDirectory)
+            {
+                if (filePath.StartsWith(projectDirectory, StringComparison.OrdinalIgnoreCase))
+                {
+                    filePath = filePath.Substring(projectDirectory.Length);
+                }
+
+                if (filePath.Length > 1)
+                {
+                    filePath = filePath.Replace('\\', '/');
+
+                    if (filePath[0] != '/')
+                    {
+                        filePath = "/" + filePath;
+                    }
+                }
+
+                return filePath;
+            }
         }
 
         private class WorkParcel

src/Microsoft.VisualStudio.Editor.Razor/DefaultImportDocumentManager.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
+using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.CodeAnalysis.Razor;
 
@@ -15,7 +16,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
         private readonly FileChangeTrackerFactory _fileChangeTrackerFactory;
         private readonly ForegroundDispatcher _foregroundDispatcher;
         private readonly ErrorReporter _errorReporter;
-        private readonly RazorTemplateEngineFactoryService _templateEngineFactoryService;
+        private readonly RazorProjectEngineFactoryService _projectEngineFactoryService;
         private readonly Dictionary<string, ImportTracker> _importTrackerCache;
 
         public override event EventHandler<ImportChangedEventArgs> Changed;
@@ -24,7 +25,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             ForegroundDispatcher foregroundDispatcher,
             ErrorReporter errorReporter,
             FileChangeTrackerFactory fileChangeTrackerFactory,
-            RazorTemplateEngineFactoryService templateEngineFactoryService)
+            RazorProjectEngineFactoryService projectEngineFactoryService)
         {
             if (foregroundDispatcher == null)
             {
@@ -41,15 +42,15 @@ namespace Microsoft.VisualStudio.Editor.Razor
                 throw new ArgumentNullException(nameof(fileChangeTrackerFactory));
             }
 
-            if (templateEngineFactoryService == null)
+            if (projectEngineFactoryService == null)
             {
-                throw new ArgumentNullException(nameof(templateEngineFactoryService));
+                throw new ArgumentNullException(nameof(projectEngineFactoryService));
             }
 
             _foregroundDispatcher = foregroundDispatcher;
             _errorReporter = errorReporter;
             _fileChangeTrackerFactory = fileChangeTrackerFactory;
-            _templateEngineFactoryService = templateEngineFactoryService;
+            _projectEngineFactoryService = projectEngineFactoryService;
             _importTrackerCache = new Dictionary<string, ImportTracker>(StringComparer.OrdinalIgnoreCase);
         }
 
@@ -115,10 +116,26 @@ namespace Microsoft.VisualStudio.Editor.Razor
         private IEnumerable<RazorProjectItem> GetImportItems(VisualStudioDocumentTracker tracker)
         {
             var projectDirectory = Path.GetDirectoryName(tracker.ProjectPath);
-            var templateEngine = _templateEngineFactoryService.Create(projectDirectory, _ => { });
+            var projectEngine = _projectEngineFactoryService.Create(projectDirectory, _ => { });
-            var imports = templateEngine.GetImportItems(tracker.FilePath);
+            var trackerItem = projectEngine.FileSystem.GetItem(tracker.FilePath);
+            var importFeature = projectEngine.ProjectFeatures.OfType<IImportProjectFeature>().FirstOrDefault();
 
-            return imports;
+            // There should always be an import feature unless someone has misconfigured their RazorProjectEngine.
+            // In that case once we attempt to parse the Razor file we'll explode and give the a user a decent
+            // error message; for now, lets just be extra protective and assume 0 imports to not give a bad error.
+            var imports = importFeature?.GetImports(trackerItem) ?? Enumerable.Empty<RazorSourceDocument>();
+            var physicalImports = imports.Where(import => import.FilePath != null);
+
+            // Now that we have non-dynamic imports we need to get their RazorProjectItem equivalents so we have their
+            // physical file paths (according to the FileSystem).
+            var projectItems = new List<RazorProjectItem>();
+            foreach (var physicalImport in physicalImports)
+            {
+                var projectItem = projectEngine.FileSystem.GetItem(physicalImport.FilePath);
+                projectItems.Add(projectItem);
+            }
+
+            return projectItems;
         }
 
         private void OnChanged(ImportTracker importTracker, FileChangeKind changeKind)

src/Microsoft.VisualStudio.Editor.Razor/DefaultImportDocumentManagerFactory.cs

@@ -35,13 +35,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
 
             var errorReporter = languageServices.WorkspaceServices.GetRequiredService<ErrorReporter>();
             var fileChangeTrackerFactory = languageServices.GetRequiredService<FileChangeTrackerFactory>();
-            var templateEngineFactoryService = languageServices.GetRequiredService<RazorTemplateEngineFactoryService>();
+            var projectEngineFactoryService = languageServices.GetRequiredService<RazorProjectEngineFactoryService>();
 
             return new DefaultImportDocumentManager(
                 _foregroundDispatcher,
                 errorReporter,
                 fileChangeTrackerFactory,
-                templateEngineFactoryService);
+                projectEngineFactoryService);
         }
     }
 }

src/Microsoft.VisualStudio.Editor.Razor/DefaultProjectEngineFactoryService.cs

@@ -12,7 +12,7 @@ using MvcLatest = Microsoft.AspNetCore.Mvc.Razor.Extensions;
 
 namespace Microsoft.VisualStudio.Editor.Razor
 {
-    internal class DefaultTemplateEngineFactoryService : RazorTemplateEngineFactoryService
+    internal class DefaultProjectEngineFactoryService : RazorProjectEngineFactoryService
     {
         private readonly static MvcExtensibilityConfiguration DefaultConfiguration = new MvcExtensibilityConfiguration(
             RazorLanguageVersion.Version_2_0,
@@ -22,7 +22,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
 
         private readonly ProjectSnapshotManager _projectManager;
 
-        public DefaultTemplateEngineFactoryService(ProjectSnapshotManager projectManager)
+        public DefaultProjectEngineFactoryService(ProjectSnapshotManager projectManager)
         {
             if (projectManager == null)
             {
@@ -32,7 +32,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             _projectManager = projectManager;
         }
 
-        public override RazorTemplateEngine Create(string projectPath, Action<IRazorEngineBuilder> configure)
+        public override RazorProjectEngine Create(string projectPath, Action<RazorProjectEngineBuilder> configure)
         {
             if (projectPath == null)
             {
@@ -43,12 +43,14 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var project = FindProject(projectPath);
             var configuration = (project?.Configuration as MvcExtensibilityConfiguration) ?? DefaultConfiguration;
             var razorLanguageVersion = configuration.LanguageVersion;
-            var razorConfiguration = new RazorConfiguration(razorLanguageVersion, "unnamed", Array.Empty<RazorExtension>());
 
-            RazorEngine engine;
+            var razorConfiguration = new RazorConfiguration(razorLanguageVersion, "unnamed", Array.Empty<RazorExtension>());
+            var fileSystem = RazorProjectFileSystem.Create(projectPath);
+
+            RazorProjectEngine projectEngine;
             if (razorLanguageVersion.Major == 1)
             {
-                engine = RazorEngine.CreateCore(razorConfiguration, true, b =>
+                projectEngine = RazorProjectEngine.Create(razorConfiguration, fileSystem, b =>
                 {
                     configure?.Invoke(b);
 
@@ -59,24 +61,18 @@ namespace Microsoft.VisualStudio.Editor.Razor
                         Mvc1_X.RazorExtensions.RegisterViewComponentTagHelpers(b);
                     }
                 });
-
-                var templateEngine = new Mvc1_X.MvcRazorTemplateEngine(engine, RazorProjectFileSystem.Create(projectPath));
-                templateEngine.Options.ImportsFileName = "_ViewImports.cshtml";
-                return templateEngine;
             }
             else
             {
-                engine = RazorEngine.CreateCore(razorConfiguration, true, b =>
+                projectEngine = RazorProjectEngine.Create(razorConfiguration, fileSystem, b =>
                 {
                     configure?.Invoke(b);
 
                     MvcLatest.RazorExtensions.Register(b);
                 });
-
-                var templateEngine = new MvcLatest.MvcRazorTemplateEngine(engine, RazorProjectFileSystem.Create(projectPath));
-                templateEngine.Options.ImportsFileName = "_ViewImports.cshtml";
-                return templateEngine;
             }
+
+            return projectEngine;
         }
 
         private ProjectSnapshot FindProject(string directory)

src/Microsoft.VisualStudio.Editor.Razor/DefaultProjectEngineFactoryServiceFactory.cs

@@ -8,12 +8,12 @@ using Microsoft.CodeAnalysis.Razor.ProjectSystem;
 
 namespace Microsoft.VisualStudio.Editor.Razor
 {
-    [ExportLanguageServiceFactory(typeof(RazorTemplateEngineFactoryService), RazorLanguage.Name, ServiceLayer.Default)]
+    [ExportLanguageServiceFactory(typeof(RazorProjectEngineFactoryService), RazorLanguage.Name, ServiceLayer.Default)]
-    internal class DefaultTemplateEngineFactoryServiceFactory : ILanguageServiceFactory
+    internal class DefaultProjectEngineFactoryServiceFactory : ILanguageServiceFactory
     {
         public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
         {
-            return new DefaultTemplateEngineFactoryService(languageServices.GetRequiredService<ProjectSnapshotManager>());
+            return new DefaultProjectEngineFactoryService(languageServices.GetRequiredService<ProjectSnapshotManager>());
         }
     }
 }

src/Microsoft.VisualStudio.Editor.Razor/DefaultVisualStudioRazorParser.cs

@@ -31,9 +31,9 @@ namespace Microsoft.VisualStudio.Editor.Razor
         private readonly VisualStudioCompletionBroker _completionBroker;
         private readonly VisualStudioDocumentTracker _documentTracker;
         private readonly ForegroundDispatcher _dispatcher;
-        private readonly RazorTemplateEngineFactoryService _templateEngineFactory;
+        private readonly RazorProjectEngineFactoryService _projectEngineFactory;
         private readonly ErrorReporter _errorReporter;
-        private RazorTemplateEngine _templateEngine;
+        private RazorProjectEngine _projectEngine;
         private RazorCodeDocument _codeDocument;
         private ITextSnapshot _snapshot;
         private bool _disposed;
@@ -47,7 +47,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
         public DefaultVisualStudioRazorParser(
             ForegroundDispatcher dispatcher,
             VisualStudioDocumentTracker documentTracker,
-            RazorTemplateEngineFactoryService templateEngineFactory,
+            RazorProjectEngineFactoryService projectEngineFactory,
             ErrorReporter errorReporter,
             VisualStudioCompletionBroker completionBroker)
         {
@@ -61,9 +61,9 @@ namespace Microsoft.VisualStudio.Editor.Razor
                 throw new ArgumentNullException(nameof(documentTracker));
             }
 
-            if (templateEngineFactory == null)
+            if (projectEngineFactory == null)
             {
-                throw new ArgumentNullException(nameof(templateEngineFactory));
+                throw new ArgumentNullException(nameof(projectEngineFactory));
             }
 
             if (errorReporter == null)
@@ -77,7 +77,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             }
 
             _dispatcher = dispatcher;
-            _templateEngineFactory = templateEngineFactory;
+            _projectEngineFactory = projectEngineFactory;
             _errorReporter = errorReporter;
             _completionBroker = completionBroker;
             _documentTracker = documentTracker;
@@ -85,7 +85,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             _documentTracker.ContextChanged += DocumentTracker_ContextChanged;
         }
 
-        public override RazorTemplateEngine TemplateEngine => _templateEngine;
+        public override RazorProjectEngine ProjectEngine => _projectEngine;
 
         public override string FilePath => _documentTracker.FilePath;
 
@@ -170,8 +170,8 @@ namespace Microsoft.VisualStudio.Editor.Razor
             _dispatcher.AssertForegroundThread();
 
             var projectDirectory = Path.GetDirectoryName(_documentTracker.ProjectPath);
-            _templateEngine = _templateEngineFactory.Create(projectDirectory, ConfigureTemplateEngine);
+            _projectEngine = _projectEngineFactory.Create(projectDirectory, ConfigureProjectEngine);
-            _parser = new BackgroundParser(TemplateEngine, FilePath);
+            _parser = new BackgroundParser(ProjectEngine, FilePath, projectDirectory);
             _parser.ResultsReady += OnResultsReady;
             _parser.Start();
 
@@ -383,7 +383,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             DocumentStructureChanged?.Invoke(this, args);
         }
 
-        private void ConfigureTemplateEngine(IRazorEngineBuilder builder)
+        private void ConfigureProjectEngine(RazorProjectEngineBuilder builder)
         {
             builder.Features.Add(new VisualStudioParserOptionsFeature(_documentTracker.EditorSettings));
             builder.Features.Add(new VisualStudioTagHelperFeature(_documentTracker.TagHelpers));

src/Microsoft.VisualStudio.Editor.Razor/DefaultVisualStudioRazorParserFactory.cs

@@ -9,7 +9,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
     internal class DefaultVisualStudioRazorParserFactory : VisualStudioRazorParserFactory
     {
         private readonly ForegroundDispatcher _dispatcher;
-        private readonly RazorTemplateEngineFactoryService _templateEngineFactoryService;
+        private readonly RazorProjectEngineFactoryService _projectEngineFactoryService;
         private readonly VisualStudioCompletionBroker _completionBroker;
         private readonly ErrorReporter _errorReporter;
 
@@ -17,7 +17,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             ForegroundDispatcher dispatcher,
             ErrorReporter errorReporter,
             VisualStudioCompletionBroker completionBroker,
-            RazorTemplateEngineFactoryService templateEngineFactoryService)
+            RazorProjectEngineFactoryService projectEngineFactoryService)
         {
             if (dispatcher == null)
             {
@@ -34,15 +34,15 @@ namespace Microsoft.VisualStudio.Editor.Razor
                 throw new ArgumentNullException(nameof(completionBroker));
             }
 
-            if (templateEngineFactoryService == null)
+            if (projectEngineFactoryService == null)
             {
-                throw new ArgumentNullException(nameof(templateEngineFactoryService));
+                throw new ArgumentNullException(nameof(projectEngineFactoryService));
             }
 
             _dispatcher = dispatcher;
             _errorReporter = errorReporter;
             _completionBroker = completionBroker;
-            _templateEngineFactoryService = templateEngineFactoryService;
+            _projectEngineFactoryService = projectEngineFactoryService;
         }
 
         public override VisualStudioRazorParser Create(VisualStudioDocumentTracker documentTracker)
@@ -57,7 +57,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var parser = new DefaultVisualStudioRazorParser(
                 _dispatcher,
                 documentTracker,
-                _templateEngineFactoryService,
+                _projectEngineFactoryService,
                 _errorReporter,
                 _completionBroker);
             return parser;

src/Microsoft.VisualStudio.Editor.Razor/DefaultVisualStudioRazorParserFactoryFactory.cs

@@ -35,13 +35,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var workspaceServices = languageServices.WorkspaceServices;
             var errorReporter = workspaceServices.GetRequiredService<ErrorReporter>();
             var completionBroker = languageServices.GetRequiredService<VisualStudioCompletionBroker>();
-            var templateEngineFactoryService = languageServices.GetRequiredService<RazorTemplateEngineFactoryService>();
+            var projectEngineFactoryService = languageServices.GetRequiredService<RazorProjectEngineFactoryService>();
 
             return new DefaultVisualStudioRazorParserFactory(
                 _foregroundDispatcher,
                 errorReporter,
                 completionBroker,
-                templateEngineFactoryService);
+                projectEngineFactoryService);
         }
     }
 }

src/Microsoft.VisualStudio.Editor.Razor/TextSnapshotProjectItem.cs

@@ -0,0 +1,65 @@
+// 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.IO;
+using System.Text;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.VisualStudio.Text;
+
+namespace Microsoft.VisualStudio.Editor.Razor
+{
+    internal class TextSnapshotProjectItem : RazorProjectItem
+    {
+        private readonly ITextSnapshot _snapshot;
+
+        public TextSnapshotProjectItem(ITextSnapshot snapshot, string projectDirectory, string relativeFilePath, string filePath)
+        {
+            if (snapshot == null)
+            {
+                throw new ArgumentNullException(nameof(snapshot));
+            }
+
+            if (string.IsNullOrEmpty(projectDirectory))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(projectDirectory));
+            }
+
+            if (string.IsNullOrEmpty(relativeFilePath))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(relativeFilePath));
+            }
+
+            if (string.IsNullOrEmpty(filePath))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(filePath));
+            }
+
+            _snapshot = snapshot;
+            BasePath = projectDirectory;
+            FilePath = relativeFilePath;
+            PhysicalPath = filePath;
+        }
+
+        public override string BasePath { get; }
+
+        public override string FilePath { get; }
+
+        public override string PhysicalPath { get; }
+
+        public override bool Exists => true;
+
+        public override Stream Read()
+        {
+            var charArray = _snapshot.ToCharArray(0, _snapshot.Length);
+
+            // We can assume UTF8 because the call path that reads from RazorProjectItem => SourceDocument
+            // can't determine the encoding and always assumes Encoding.UTF8. This is something that we might
+            // want to revisit in the future.
+            var bytes = Encoding.UTF8.GetBytes(charArray);
+            var memoryStream = new MemoryStream(bytes);
+            return memoryStream;
+        }
+    }
+
+}

src/Microsoft.VisualStudio.Editor.Razor/TextSnapshotSourceDocument.cs

@@ -1,79 +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 System.Text;
-using Microsoft.AspNetCore.Razor.Language;
-using Microsoft.VisualStudio.Text;
-
-namespace Microsoft.VisualStudio.Editor.Razor
-{
-    internal class TextSnapshotSourceDocument : RazorSourceDocument
-    {
-        private readonly ITextSnapshot _buffer;
-        private readonly RazorSourceLineCollection _lines;
-
-        public TextSnapshotSourceDocument(ITextSnapshot snapshot, string filePath)
-        {
-            if (snapshot == null)
-            {
-                throw new ArgumentNullException(nameof(snapshot));
-            }
-
-            if (filePath == null)
-            {
-                throw new ArgumentNullException(nameof(filePath));
-            }
-
-            _buffer = snapshot;
-            FilePath = filePath;
-
-            _lines = new DefaultRazorSourceLineCollection(this);
-        }
-
-        public override char this[int position] => _buffer[position];
-
-        public override Encoding Encoding => Encoding.UTF8;
-
-        public override int Length => _buffer.Length;
-
-        public override RazorSourceLineCollection Lines => _lines;
-
-        public override string FilePath { get; }
-        
-        public override void CopyTo(int sourceIndex, char[] destination, int destinationIndex, int count)
-        {
-            if (destination == null)
-            {
-                throw new ArgumentNullException(nameof(destination));
-            }
-
-            if (sourceIndex < 0)
-            {
-                throw new ArgumentOutOfRangeException(nameof(sourceIndex));
-            }
-
-            if (destinationIndex < 0)
-            {
-                throw new ArgumentOutOfRangeException(nameof(destinationIndex));
-            }
-
-            if (count < 0 || count > Length - sourceIndex || count > destination.Length - destinationIndex)
-            {
-                throw new ArgumentOutOfRangeException(nameof(count));
-            }
-
-            if (count == 0)
-            {
-                return;
-            }
-
-            for (var i = 0; i < count; i++)
-            {
-                destination[destinationIndex + i] = this[sourceIndex + i];
-            }
-        }
-
-        public override byte[] GetChecksum() => throw new NotImplementedException();
-    }
-}

src/Microsoft.VisualStudio.Editor.Razor/VisualStudioRazorParser.cs

@@ -11,7 +11,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
     {
         public abstract event EventHandler<DocumentStructureChangedEventArgs> DocumentStructureChanged;
 
-        public abstract RazorTemplateEngine TemplateEngine { get; }
+        public abstract RazorProjectEngine ProjectEngine { get; }
 
         public abstract string FilePath { get; }
 

src/RazorPageGenerator/Program.cs

@@ -31,8 +31,8 @@ Examples:
 
             var rootNamespace = args[0];
             var targetProjectDirectory = args.Length > 1 ? args[1] : Directory.GetCurrentDirectory();
-            var razorEngine = CreateRazorEngine(rootNamespace);
+            var projectEngine = CreateProjectEngine(rootNamespace, targetProjectDirectory);
-            var results = MainCore(razorEngine, targetProjectDirectory);
+            var results = MainCore(projectEngine, targetProjectDirectory);
 
             foreach (var result in results)
             {
@@ -45,9 +45,10 @@ Examples:
             return 0;
         }
 
-        public static RazorEngine CreateRazorEngine(string rootNamespace, Action<IRazorEngineBuilder> configure = null)
+        public static RazorProjectEngine CreateProjectEngine(string rootNamespace, string targetProjectDirectory, Action<RazorProjectEngineBuilder> configure = null)
         {
-            var razorEngine = RazorEngine.Create(builder =>
+            var fileSystem = RazorProjectFileSystem.Create(targetProjectDirectory);
+            var projectEngine = RazorProjectEngine.Create(RazorConfiguration.Default, fileSystem, builder =>
             {
                 builder
                     .SetNamespace(rootNamespace)
@@ -66,20 +67,18 @@ Examples:
                 {
                     configure(builder);
                 }
-            });
-            return razorEngine;
-        }
 
-        public static IList<RazorPageGeneratorResult> MainCore(RazorEngine razorEngine, string targetProjectDirectory)
+                builder.AddDefaultImports(RazorSourceDocument.Create(@"
-        {
-            var viewDirectories = Directory.EnumerateDirectories(targetProjectDirectory, "Views", SearchOption.AllDirectories);
-            var razorProject = RazorProjectFileSystem.Create(targetProjectDirectory);
-            var templateEngine = new RazorTemplateEngine(razorEngine, razorProject);
-            templateEngine.Options.DefaultImports = RazorSourceDocument.Create(@"
 @using System
 @using System.Threading.Tasks
-", fileName: null);
+", fileName: null));
+            });
+            return projectEngine;
+        }
 
+        public static IList<RazorPageGeneratorResult> MainCore(RazorProjectEngine projectEngine, string targetProjectDirectory)
+        {
+            var viewDirectories = Directory.EnumerateDirectories(targetProjectDirectory, "Views", SearchOption.AllDirectories);
             var fileCount = 0;
 
             var results = new List<RazorPageGeneratorResult>();
@@ -88,7 +87,7 @@ Examples:
                 Console.WriteLine();
                 Console.WriteLine("  Generating code files for views in {0}", viewDir);
                 var viewDirPath = viewDir.Substring(targetProjectDirectory.Length).Replace('\\', '/');
-                var cshtmlFiles = razorProject.EnumerateItems(viewDirPath);
+                var cshtmlFiles = projectEngine.FileSystem.EnumerateItems(viewDirPath);
 
                 if (!cshtmlFiles.Any())
                 {
@@ -99,7 +98,7 @@ Examples:
                 foreach (var item in cshtmlFiles)
                 {
                     Console.WriteLine("    Generating code file for view {0}...", item.FileName);
-                    results.Add(GenerateCodeFile(templateEngine, item));
+                    results.Add(GenerateCodeFile(projectEngine, item));
                     Console.WriteLine("      Done!");
                     fileCount++;
                 }
@@ -108,10 +107,11 @@ Examples:
             return results;
         }
 
-        private static RazorPageGeneratorResult GenerateCodeFile(RazorTemplateEngine templateEngine, RazorProjectItem projectItem)
+        private static RazorPageGeneratorResult GenerateCodeFile(RazorProjectEngine projectEngine, RazorProjectItem projectItem)
         {
             var projectItemWrapper = new FileSystemRazorProjectItemWrapper(projectItem);
-            var cSharpDocument = templateEngine.GenerateCode(projectItemWrapper);
+            var codeDocument = projectEngine.Process(projectItemWrapper);
+            var cSharpDocument = codeDocument.GetCSharpDocument();
             if (cSharpDocument.Diagnostics.Any())
             {
                 var diagnostics = string.Join(Environment.NewLine, cSharpDocument.Diagnostics);

test/Microsoft.AspNetCore.Razor.Test.Common/Language/RazorProjectEngineBuilderExtensions.cs

@@ -0,0 +1,70 @@
+// 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 System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Language.IntegrationTests;
+using Microsoft.AspNetCore.Razor.Language.Intermediate;
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    public static class RazorProjectEngineBuilderExtensions
+    {
+        public static RazorProjectEngineBuilder AddTagHelpers(this RazorProjectEngineBuilder builder, params TagHelperDescriptor[] tagHelpers)
+        {
+            return AddTagHelpers(builder, (IEnumerable<TagHelperDescriptor>)tagHelpers);
+        }
+
+        public static RazorProjectEngineBuilder AddTagHelpers(this RazorProjectEngineBuilder builder, IEnumerable<TagHelperDescriptor> tagHelpers)
+        {
+            var feature = (TestTagHelperFeature)builder.Features.OfType<ITagHelperFeature>().FirstOrDefault();
+            if (feature == null)
+            {
+                feature = new TestTagHelperFeature();
+                builder.Features.Add(feature);
+            }
+
+            feature.TagHelpers.AddRange(tagHelpers);
+            return builder;
+        }
+
+        public static RazorProjectEngineBuilder ConfigureDocumentClassifier(this RazorProjectEngineBuilder builder)
+        {
+            var feature = builder.Features.OfType<DefaultDocumentClassifierPassFeature>().FirstOrDefault();
+            if (feature == null)
+            {
+                feature = new DefaultDocumentClassifierPassFeature();
+                builder.Features.Add(feature);
+            }
+
+            feature.ConfigureNamespace.Clear();
+            feature.ConfigureClass.Clear();
+            feature.ConfigureMethod.Clear();
+
+            feature.ConfigureNamespace.Add((RazorCodeDocument codeDocument, NamespaceDeclarationIntermediateNode node) =>
+            {
+                node.Content = "Microsoft.AspNetCore.Razor.Language.IntegrationTests.TestFiles";
+            });
+
+            feature.ConfigureClass.Add((RazorCodeDocument codeDocument, ClassDeclarationIntermediateNode node) =>
+            {
+                node.ClassName = IntegrationTestBase.FileName.Replace('/', '_');
+                node.Modifiers.Clear();
+                node.Modifiers.Add("public");
+            });
+
+            feature.ConfigureMethod.Add((RazorCodeDocument codeDocument, MethodDeclarationIntermediateNode node) =>
+            {
+                node.Modifiers.Clear();
+                node.Modifiers.Add("public");
+                node.Modifiers.Add("async");
+                node.MethodName = "ExecuteAsync";
+                node.ReturnType = typeof(Task).FullName;
+            });
+
+            return builder;
+        }
+    }
+}

test/Microsoft.AspNetCore.Razor.Test.Common/Language/TestRazorProjectFileSystem.cs

@@ -4,11 +4,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
-    public class TestRazorProjectFileSystem : RazorProjectFileSystem
+    internal class TestRazorProjectFileSystem : DefaultRazorProjectFileSystem
     {
         public static RazorProjectFileSystem Empty = new TestRazorProjectFileSystem();
 
@@ -19,7 +18,7 @@ namespace Microsoft.AspNetCore.Razor.Language
         {
         }
 
-        public TestRazorProjectFileSystem(IList<RazorProjectItem> items)
+        public TestRazorProjectFileSystem(IList<RazorProjectItem> items) : base("/")
         {
             _lookup = items.ToDictionary(item => item.FilePath);
         }

test/Microsoft.AspNetCore.Razor.Test.Common/Properties/AssemblyInfo.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.Runtime.CompilerServices;
+[assembly: InternalsVisibleTo("Microsoft.AspNetCore.Mvc.Razor.Extensions.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.AspNetCore.Razor.Language.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Workspaces.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultImportDocumentManagerIntegrationTest.cs

@@ -21,7 +21,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var testImportsPath = "C:\\path\\to\\project\\_ViewImports.cshtml";
             var tracker = Mock.Of<VisualStudioDocumentTracker>(t => t.FilePath == filePath && t.ProjectPath == projectPath);
             var anotherTracker = Mock.Of<VisualStudioDocumentTracker>(t => t.FilePath == anotherFilePath && t.ProjectPath == projectPath);
-            var templateEngineFactoryService = GetTemplateEngineFactoryService();
+            var templateEngineFactoryService = GetProjectEngineFactoryService();
             var fileChangeTracker = new Mock<FileChangeTracker>();
             fileChangeTracker.Setup(f => f.FilePath).Returns(testImportsPath);
             var fileChangeTrackerFactory = new Mock<FileChangeTrackerFactory>();
@@ -58,12 +58,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
             Assert.True(called);
         }
 
-        private RazorTemplateEngineFactoryService GetTemplateEngineFactoryService()
+        private RazorProjectEngineFactoryService GetProjectEngineFactoryService()
         {
             var projectManager = new Mock<ProjectSnapshotManager>();
             projectManager.Setup(p => p.Projects).Returns(Array.Empty<ProjectSnapshot>());
 
-            var service = new DefaultTemplateEngineFactoryService(projectManager.Object);
+            var service = new DefaultProjectEngineFactoryService(projectManager.Object);
             return service;
         }
     }

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultImportDocumentManagerTest.cs

@@ -137,12 +137,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
             manager.OnUnsubscribed(tracker);
         }
 
-        private RazorTemplateEngineFactoryService GetTemplateEngineFactoryService()
+        private RazorProjectEngineFactoryService GetTemplateEngineFactoryService()
         {
             var projectManager = new Mock<ProjectSnapshotManager>();
             projectManager.Setup(p => p.Projects).Returns(Array.Empty<ProjectSnapshot>());
 
-            var service = new DefaultTemplateEngineFactoryService(projectManager.Object);
+            var service = new DefaultProjectEngineFactoryService(projectManager.Object);
             return service;
         }
     }

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultProjectEngineFactoryServiceTest.cs

@@ -14,9 +14,9 @@ using MvcLatest = Microsoft.AspNetCore.Mvc.Razor.Extensions;
 
 namespace Microsoft.VisualStudio.Editor.Razor
 {
-    public class DefaultTemplateEngineFactoryServiceTest
+    public class DefaultProjectEngineFactoryServiceTest
     {
-        public DefaultTemplateEngineFactoryServiceTest()
+        public DefaultProjectEngineFactoryServiceTest()
         {
             Project project = null;
 
@@ -35,7 +35,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
         public Workspace Workspace { get; }
 
         [Fact]
-        public void Create_CreatesDesignTimeTemplateEngine_ForLatest()
+        public void Create_CreatesTemplateEngine_ForLatest()
         {
             // Arrange
             var projectManager = new TestProjectSnapshotManager(Workspace);
@@ -49,13 +49,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
                     new ProjectExtensibilityAssembly(new AssemblyIdentity("Microsoft.AspNetCore.Razor", new Version("2.0.0.0")))),
             });
 
-            var factoryService = new DefaultTemplateEngineFactoryService(projectManager);
+            var factoryService = new DefaultProjectEngineFactoryService(projectManager);
 
             // Act
             var engine = factoryService.Create("/TestPath/SomePath/", b =>
             {
                 b.Features.Add(new MyCoolNewFeature());
-                Assert.True(b.DesignTime);
             });
 
             // Assert
@@ -65,7 +64,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
         }
 
         [Fact]
-        public void Create_CreatesDesignTimeTemplateEngine_ForVersion1_1()
+        public void Create_CreatesTemplateEngine_ForVersion1_1()
         {
             // Arrange
             var projectManager = new TestProjectSnapshotManager(Workspace);
@@ -79,13 +78,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
                     new ProjectExtensibilityAssembly(new AssemblyIdentity("Microsoft.AspNetCore.Razor", new Version("1.1.3.0")))),
             });
 
-            var factoryService = new DefaultTemplateEngineFactoryService(projectManager);
+            var factoryService = new DefaultProjectEngineFactoryService(projectManager);
 
             // Act
             var engine = factoryService.Create("/TestPath/SomePath/", b =>
             {
                 b.Features.Add(new MyCoolNewFeature());
-                Assert.True(b.DesignTime);
             });
 
             // Assert
@@ -109,7 +107,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
                     new ProjectExtensibilityAssembly(new AssemblyIdentity("Microsoft.AspNetCore.Razor", new Version("1.0.0.0")))),
             });
 
-            var factoryService = new DefaultTemplateEngineFactoryService(projectManager);
+            var factoryService = new DefaultProjectEngineFactoryService(projectManager);
 
             // Act
             var engine = factoryService.Create("/TestPath/SomePath/", b =>
@@ -138,13 +136,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
                     new ProjectExtensibilityAssembly(new AssemblyIdentity("Microsoft.AspNetCore.Razor", new Version("3.0.0.0")))),
             });
 
-            var factoryService = new DefaultTemplateEngineFactoryService(projectManager);
+            var factoryService = new DefaultProjectEngineFactoryService(projectManager);
 
             // Act
             var engine = factoryService.Create("/TestPath/SomePath/", b =>
             {
                 b.Features.Add(new MyCoolNewFeature());
-                Assert.True(b.DesignTime);
             });
 
             // Assert
@@ -159,13 +156,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
             // Arrange
             var projectManager = new TestProjectSnapshotManager(Workspace);
 
-            var factoryService = new DefaultTemplateEngineFactoryService(projectManager);
+            var factoryService = new DefaultProjectEngineFactoryService(projectManager);
 
             // Act
             var engine = factoryService.Create("/TestPath/DifferentPath/", b =>
             {
                 b.Features.Add(new MyCoolNewFeature());
-                Assert.True(b.DesignTime);
             });
 
             // Assert
@@ -181,13 +177,12 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var projectManager = new TestProjectSnapshotManager(Workspace);
             projectManager.ProjectAdded(Project);
 
-            var factoryService = new DefaultTemplateEngineFactoryService(projectManager);
+            var factoryService = new DefaultProjectEngineFactoryService(projectManager);
 
             // Act
             var engine = factoryService.Create("/TestPath/DifferentPath/", b =>
             {
                 b.Features.Add(new MyCoolNewFeature());
-                Assert.True(b.DesignTime);
             });
 
             // Assert

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultVisualStudioRazorParserIntegrationTest.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Linq;
 using System.Threading;
@@ -525,34 +524,27 @@ namespace Microsoft.VisualStudio.Editor.Razor
             return new TestParserManager(parser);
         }
 
-        private static RazorTemplateEngineFactoryService CreateTemplateEngineFactory(
+        private static RazorProjectEngineFactoryService CreateTemplateEngineFactory(
             string path = TestLinePragmaFileName,
             IEnumerable<TagHelperDescriptor> tagHelpers = null)
         {
-            var engine = RazorEngine.CreateDesignTime(builder =>
+            var fileSystem = new TestRazorProjectFileSystem();
+            var projectEngine = RazorProjectEngine.Create(RazorConfiguration.Default, fileSystem, builder =>
             {
                 RazorExtensions.Register(builder);
 
+                builder.AddDefaultImports(RazorSourceDocument.Create("@addTagHelper *, Test", "_TestImports.cshtml"));
+
                 if (tagHelpers != null)
                 {
                     builder.AddTagHelpers(tagHelpers);
                 }
             });
 
-            // GetImports on RazorTemplateEngine will at least check that the item exists, so we need to pretend
+            var projectEngineFactoryService = Mock.Of<RazorProjectEngineFactoryService>(
-            // that it does.
+                service => service.Create(It.IsAny<string>(), It.IsAny<Action<RazorProjectEngineBuilder>>()) == projectEngine);
-            var items = new List<RazorProjectItem>();
-            items.Add(new TestRazorProjectItem(path));
 
-            var project = new TestRazorProjectFileSystem(items);
+            return projectEngineFactoryService;
-
-            var templateEngine = new RazorTemplateEngine(engine, project);
-            templateEngine.Options.DefaultImports = RazorSourceDocument.Create("@addTagHelper *, Test", "_TestImports.cshtml");
-
-            var templateEngineFactory = Mock.Of<RazorTemplateEngineFactoryService>(
-                service => service.Create(It.IsAny<string>(), It.IsAny<Action<IRazorEngineBuilder>>()) == templateEngine);
-
-            return templateEngineFactory;
         }
 
         private async Task RunTypeKeywordTestAsync(string keyword)

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultVisualStudioRazorParserTest.cs

@@ -32,7 +32,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>());
             parser.Dispose();
@@ -48,7 +48,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>());
             parser.Dispose();
@@ -64,7 +64,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>());
             parser.Dispose();
@@ -80,7 +80,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>()))
             {
@@ -108,7 +108,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 documentTracker,
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>()))
             {
@@ -139,7 +139,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>())
             {
@@ -169,7 +169,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>())
             {
@@ -198,7 +198,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>()))
             {
@@ -222,7 +222,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 documentTracker,
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>()))
             {
@@ -242,7 +242,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(isSupportedProject: true),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>()))
             {
@@ -261,7 +261,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             using (var parser = new DefaultVisualStudioRazorParser(
                 Dispatcher,
                 CreateDocumentTracker(isSupportedProject: false),
-                Mock.Of<RazorTemplateEngineFactoryService>(),
+                Mock.Of<RazorProjectEngineFactoryService>(),
                 new DefaultErrorReporter(),
                 Mock.Of<VisualStudioCompletionBroker>()))
             {

test/Microsoft.VisualStudio.Editor.Razor.Test/RazorSyntaxTreePartialParserTest.cs

@@ -3,14 +3,12 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using Microsoft.AspNetCore.Mvc.Razor.Extensions;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
 using Microsoft.VisualStudio.Test;
 using Microsoft.VisualStudio.Text;
 using Xunit;
-using Span = Microsoft.AspNetCore.Razor.Language.Legacy.Span;
 
 namespace Microsoft.VisualStudio.Editor.Razor
 {
@@ -44,12 +42,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
             {
                 builder.Build()
             };
-            var templateEngine = CreateTemplateEngine(tagHelpers: descriptors);
+            var projectEngine = CreateProjectEngine(tagHelpers: descriptors);
-            var document = TestRazorCodeDocument.Create(
+            var projectItem = new TestRazorProjectItem("Index.cshtml")
-                TestRazorSourceDocument.Create(edit.OldSnapshot.GetText()),
+            {
-                new[] { templateEngine.Options.DefaultImports });
+                Content = edit.OldSnapshot.GetText()
-            templateEngine.Engine.Process(document);
+            };
-            var syntaxTree = document.GetSyntaxTree();
+            var codeDocument = projectEngine.Process(projectItem);
+            var syntaxTree = codeDocument.GetSyntaxTree();
             var parser = new RazorSyntaxTreePartialParser(syntaxTree);
 
             // Act
@@ -115,12 +114,13 @@ namespace Microsoft.VisualStudio.Editor.Razor
                 attribute.SetPropertyName("StringAttribute");
             });
             var descriptors = new[] { builder.Build() };
-            var templateEngine = CreateTemplateEngine(tagHelpers: descriptors);
+            var projectEngine = CreateProjectEngine(tagHelpers: descriptors);
-            var document = TestRazorCodeDocument.Create(
+            var sourceDocument = new TestRazorProjectItem("Index.cshtml")
-                TestRazorSourceDocument.Create(edit.OldSnapshot.GetText()),
+            {
-                new[] { templateEngine.Options.DefaultImports });
+                Content = edit.OldSnapshot.GetText()
-            templateEngine.Engine.Process(document);
+            };
-            var syntaxTree = document.GetSyntaxTree();
+            var codeDocument = projectEngine.Process(sourceDocument);
+            var syntaxTree = codeDocument.GetSyntaxTree();
             var parser = new RazorSyntaxTreePartialParser(syntaxTree);
 
             // Act
@@ -548,7 +548,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
 
         private void RunPartialParseRejectionTest(TestEdit edit, PartialParseResultInternal additionalFlags = 0)
         {
-            var templateEngine = CreateTemplateEngine();
+            var templateEngine = CreateProjectEngine();
             var document = TestRazorCodeDocument.Create(edit.OldSnapshot.GetText());
             templateEngine.Engine.Process(document);
             var syntaxTree = document.GetSyntaxTree();
@@ -560,7 +560,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
 
         private static void RunPartialParseTest(TestEdit edit, Block expectedTree, PartialParseResultInternal additionalFlags = 0)
         {
-            var templateEngine = CreateTemplateEngine();
+            var templateEngine = CreateProjectEngine();
             var document = TestRazorCodeDocument.Create(edit.OldSnapshot.GetText());
             templateEngine.Engine.Process(document);
             var syntaxTree = document.GetSyntaxTree();
@@ -580,30 +580,24 @@ namespace Microsoft.VisualStudio.Editor.Razor
             return new TestEdit(sourceChange, oldSnapshot, changedSnapshot);
         }
 
-        private static RazorTemplateEngine CreateTemplateEngine(
+        private static RazorProjectEngine CreateProjectEngine(
             string path = "C:\\This\\Path\\Is\\Just\\For\\Line\\Pragmas.cshtml",
             IEnumerable<TagHelperDescriptor> tagHelpers = null)
         {
-            var engine = RazorEngine.CreateDesignTime(builder =>
+            var fileSystem = new TestRazorProjectFileSystem();
+            var projectEngine = RazorProjectEngine.Create(RazorConfiguration.Default, fileSystem, builder =>
             {
                 RazorExtensions.Register(builder);
 
+                builder.AddDefaultImports(RazorSourceDocument.Create("@addTagHelper *, Test", "_TestImports.cshtml"));
+
                 if (tagHelpers != null)
                 {
                     builder.AddTagHelpers(tagHelpers);
                 }
             });
 
-            // GetImports on RazorTemplateEngine will at least check that the item exists, so we need to pretend
+            return projectEngine;
-            // that it does.
-            var items = new List<RazorProjectItem>();
-            items.Add(new TestRazorProjectItem(path));
-
-            var project = new TestRazorProjectFileSystem(items);
-
-            var templateEngine = new RazorTemplateEngine(engine, project);
-            templateEngine.Options.DefaultImports = RazorSourceDocument.Create("@addTagHelper *, Test", "_TestImports.cshtml");
-            return templateEngine;
         }
     }
 }

test/RazorPageGenerator.Test/RazorPageGeneratorTest.cs

@@ -35,9 +35,10 @@ namespace RazorPageGenerator.Test
         {
             // Arrange
             var projectDirectory = TestProject.GetProjectDirectory(GetType());
-            var razorEngine = Program.CreateRazorEngine("Microsoft.AspNetCore.TestGenerated");
+            var projectEngine = Program.CreateProjectEngine("Microsoft.AspNetCore.TestGenerated", projectDirectory);
+
             // Act
-            var results = Program.MainCore(razorEngine, projectDirectory);
+            var results = Program.MainCore(projectEngine, projectDirectory);
 
             // Assert
             Assert.Collection(results,