Add MVC support for RazorProjectEngine.

- Make `RazorProjectEngine` call paths for all feature registrations.
- Add `DefaultMvcImportFeature` for latest and 1.X MVC.
- Ported `AddTargetExtension` and `AddDirective` to `RazorProjectEngineBuilderExtensions`.
- Added tests and a test file system project type.
- Moved obsolete `IRazorEngineBuilder` methods to the bottom of each file. Will actually obsolete the methods once `RazorProjectEngine` is working end-to-end.

#1828

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

@@ -0,0 +1,84 @@
+// 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.Mvc.Razor.Extensions.Version1_X
+{
+    internal class DefaultMvcImportFeature : RazorProjectEngineFeatureBase, IRazorImportFeature
+    {
+        private const string ImportsFileName = "_ViewImports.cshtml";
+
+        public IReadOnlyList<RazorSourceDocument> GetImports(string sourceFilePath)
+        {
+            if (string.IsNullOrEmpty(sourceFilePath))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpy, nameof(sourceFilePath));
+            }
+
+            var imports = new List<RazorSourceDocument>();
+            AddDefaultDirectivesImport(imports);
+
+            // We add hierarchical imports second so any default directive imports can be overridden.
+            AddHierarchicalImports(sourceFilePath, imports);
+
+            return imports;
+        }
+
+        // Internal for testing
+        internal static void AddDefaultDirectivesImport(List<RazorSourceDocument> imports)
+        {
+            using (var stream = new MemoryStream())
+            using (var writer = new StreamWriter(stream, Encoding.UTF8))
+            {
+                writer.WriteLine("@using System");
+                writer.WriteLine("@using System.Collections.Generic");
+                writer.WriteLine("@using System.Linq");
+                writer.WriteLine("@using System.Threading.Tasks");
+                writer.WriteLine("@using Microsoft.AspNetCore.Mvc");
+                writer.WriteLine("@using Microsoft.AspNetCore.Mvc.Rendering");
+                writer.WriteLine("@using Microsoft.AspNetCore.Mvc.ViewFeatures");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.Rendering.IHtmlHelper<TModel> Html");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.Rendering.IJsonHelper Json");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.IViewComponentHelper Component");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.IUrlHelper Url");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.ViewFeatures.IModelExpressionProvider ModelExpressionProvider");
+                writer.WriteLine("@addTagHelper Microsoft.AspNetCore.Mvc.Razor.TagHelpers.UrlResolutionTagHelper, Microsoft.AspNetCore.Mvc.Razor");
+                writer.Flush();
+
+                stream.Position = 0;
+                var defaultMvcImports = RazorSourceDocument.ReadFrom(stream, fileName: null, encoding: Encoding.UTF8);
+                imports.Add(defaultMvcImports);
+            }
+        }
+
+        // Internal for testing
+        internal void AddHierarchicalImports(string sourceFilePath, List<RazorSourceDocument> imports)
+        {
+            // We want items in descending order. FindHierarchicalItems returns items in ascending order.
+            var importProjectItems = ProjectEngine.FileSystem.FindHierarchicalItems(sourceFilePath, ImportsFileName).Reverse();
+            foreach (var importProjectItem in importProjectItems)
+            {
+                RazorSourceDocument importSourceDocument;
+
+                if (importProjectItem.Exists)
+                {
+                    importSourceDocument = RazorSourceDocument.ReadFrom(importProjectItem);
+                }
+                else
+                {
+                    // File doesn't exist on disk so just add a marker source document as an identifier for "there could be something here".
+                    var sourceDocumentProperties = new RazorSourceDocumentProperties(importProjectItem.FilePath, importProjectItem.RelativePhysicalPath);
+                    importSourceDocument = RazorSourceDocument.Create(string.Empty, sourceDocumentProperties);
+                }
+
+                imports.Add(importSourceDocument);
+            }
+        }
+    }
+}

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

@@ -24,8 +24,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
                 builder.Description = Resources.InjectDirective_Description;
             });
 
-        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        public static RazorProjectEngineBuilder Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new Pass());
             builder.AddTargetExtension(new InjectTargetExtension());
@@ -99,5 +104,20 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
                 }
             }
         }
+
+        #region Obsolete
+        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new Pass());
+            builder.AddTargetExtension(new InjectTargetExtension());
+            return builder;
+        }
+        #endregion
     }
 }

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

@@ -21,8 +21,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
                 builder.Description = Resources.ModelDirective_Description;
             });
 
-        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        public static RazorProjectEngineBuilder Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new Pass(builder.DesignTime));
             return builder;
@@ -128,5 +133,19 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
                 }
             }
         }
+
+        #region Obsolete
+        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new Pass(builder.DesignTime));
+            return builder;
+        }
+        #endregion
     }
 }

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

@@ -9,8 +9,68 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
 {
     public static class RazorExtensions
     {
+        public static void Register(RazorProjectEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            EnsureDesignTime(builder);
+
+            InjectDirective.Register(builder);
+            ModelDirective.Register(builder);
+
+            FunctionsDirective.Register(builder);
+            InheritsDirective.Register(builder);
+
+            // Register section directive with the 1.x compatible target extension.
+            builder.AddDirective(SectionDirective.Directive);
+            builder.Features.Add(new SectionDirectivePass());
+            builder.AddTargetExtension(new LegacySectionTargetExtension());
+
+            builder.AddTargetExtension(new TemplateTargetExtension()
+            {
+                TemplateTypeName = "global::Microsoft.AspNetCore.Mvc.Razor.HelperResult",
+            });
+
+            builder.Features.Add(new ModelExpressionPass());
+            builder.Features.Add(new MvcViewDocumentClassifierPass());
+
+            builder.SetImportFeature(new DefaultMvcImportFeature());
+        }
+
+        public static void RegisterViewComponentTagHelpers(RazorProjectEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            EnsureDesignTime(builder);
+
+            builder.Features.Add(new ViewComponentTagHelperPass());
+            builder.AddTargetExtension(new ViewComponentTagHelperTargetExtension());
+        }
+
+        private static void EnsureDesignTime(RazorProjectEngineBuilder builder)
+        {
+            if (builder.DesignTime)
+            {
+                return;
+            }
+
+            throw new NotSupportedException(Resources.RuntimeCodeGenerationNotSupported);
+        }
+
+        #region Obsolete
         public static void Register(IRazorEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             EnsureDesignTime(builder);
 
             InjectDirective.Register(builder);
@@ -35,6 +95,11 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
 
         public static void RegisterViewComponentTagHelpers(IRazorEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             EnsureDesignTime(builder);
 
             builder.Features.Add(new ViewComponentTagHelperPass());
@@ -50,5 +115,6 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
 
             throw new NotSupportedException(Resources.RuntimeCodeGenerationNotSupported);
         }
+        #endregion
     }
 }

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

@@ -0,0 +1,86 @@
+// 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.Mvc.Razor.Extensions
+{
+    internal class DefaultMvcImportFeature : RazorProjectEngineFeatureBase, IRazorImportFeature
+    {
+        private const string ImportsFileName = "_ViewImports.cshtml";
+
+        public IReadOnlyList<RazorSourceDocument> GetImports(string sourceFilePath)
+        {
+            if (string.IsNullOrEmpty(sourceFilePath))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpy, nameof(sourceFilePath));
+            }
+
+            var imports = new List<RazorSourceDocument>();
+            AddDefaultDirectivesImport(imports);
+
+            // We add hierarchical imports second so any default directive imports can be overridden.
+            AddHierarchicalImports(sourceFilePath, imports);
+
+            return imports;
+        }
+
+        // Internal for testing
+        internal static void AddDefaultDirectivesImport(List<RazorSourceDocument> imports)
+        {
+            using (var stream = new MemoryStream())
+            using (var writer = new StreamWriter(stream, Encoding.UTF8))
+            {
+                writer.WriteLine("@using System");
+                writer.WriteLine("@using System.Collections.Generic");
+                writer.WriteLine("@using System.Linq");
+                writer.WriteLine("@using System.Threading.Tasks");
+                writer.WriteLine("@using Microsoft.AspNetCore.Mvc");
+                writer.WriteLine("@using Microsoft.AspNetCore.Mvc.Rendering");
+                writer.WriteLine("@using Microsoft.AspNetCore.Mvc.ViewFeatures");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.Rendering.IHtmlHelper<TModel> Html");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.Rendering.IJsonHelper Json");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.IViewComponentHelper Component");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.IUrlHelper Url");
+                writer.WriteLine("@inject global::Microsoft.AspNetCore.Mvc.ViewFeatures.IModelExpressionProvider ModelExpressionProvider");
+                writer.WriteLine("@addTagHelper Microsoft.AspNetCore.Mvc.Razor.TagHelpers.UrlResolutionTagHelper, Microsoft.AspNetCore.Mvc.Razor");
+                writer.WriteLine("@addTagHelper Microsoft.AspNetCore.Mvc.Razor.TagHelpers.HeadTagHelper, Microsoft.AspNetCore.Mvc.Razor");
+                writer.WriteLine("@addTagHelper Microsoft.AspNetCore.Mvc.Razor.TagHelpers.BodyTagHelper, Microsoft.AspNetCore.Mvc.Razor");
+                writer.Flush();
+
+                stream.Position = 0;
+                var defaultMvcImports = RazorSourceDocument.ReadFrom(stream, fileName: null, encoding: Encoding.UTF8);
+                imports.Add(defaultMvcImports);
+            }
+        }
+
+        // Internal for testing
+        internal void AddHierarchicalImports(string sourceFilePath, List<RazorSourceDocument> imports)
+        {
+            // We want items in descending order. FindHierarchicalItems returns items in ascending order.
+            var importProjectItems = ProjectEngine.FileSystem.FindHierarchicalItems(sourceFilePath, ImportsFileName).Reverse();
+            foreach (var importProjectItem in importProjectItems)
+            {
+                RazorSourceDocument importSourceDocument;
+
+                if (importProjectItem.Exists)
+                {
+                    importSourceDocument = RazorSourceDocument.ReadFrom(importProjectItem);
+                }
+                else
+                {
+                    // File doesn't exist on disk so just add a marker source document as an identifier for "there could be something here".
+                    var sourceDocumentProperties = new RazorSourceDocumentProperties(importProjectItem.FilePath, importProjectItem.RelativePhysicalPath);
+                    importSourceDocument = RazorSourceDocument.Create(string.Empty, sourceDocumentProperties);
+                }
+
+                imports.Add(importSourceDocument);
+            }
+        }
+    }
+}

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

@@ -24,8 +24,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 builder.Description = Resources.InjectDirective_Description;
             });
 
-        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        public static RazorProjectEngineBuilder Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new Pass());
             builder.AddTargetExtension(new InjectTargetExtension());
@@ -99,5 +104,20 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 }
             }
         }
+
+        #region Obsolete
+        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new Pass());
+            builder.AddTargetExtension(new InjectTargetExtension());
+            return builder;
+        }
+        #endregion
     }
 }

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

@@ -21,8 +21,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 builder.Description = Resources.ModelDirective_Description;
             });
 
-        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        public static RazorProjectEngineBuilder Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new Pass(builder.DesignTime));
             return builder;
@@ -135,5 +140,19 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 }
             }
         }
+
+        #region Obsolete
+        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new Pass(builder.DesignTime));
+            return builder;
+        }
+        #endregion
     }
 }

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

@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 builder.Description = Resources.NamespaceDirective_Description;
             });
 
-        public static void Register(IRazorEngineBuilder builder)
+        public static void Register(RazorProjectEngineBuilder builder)
         {
             if (builder == null)
             {
@@ -186,5 +186,18 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 base.VisitDirective(node);
             }
         }
+
+        #region Obsolete
+        public static void Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException();
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new Pass());
+        }
+        #endregion
     }
 }

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

@@ -32,8 +32,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
 
         public IntermediateNode DirectiveNode { get; }
 
-        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        public static RazorProjectEngineBuilder Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             return builder;
         }
@@ -98,5 +103,18 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 }
             }
         }
+
+        #region Obsolete
+        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            return builder;
+        }
+        #endregion
     }
 }

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

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Razor.Language;
 using Microsoft.AspNetCore.Razor.Language.Extensions;
 
@@ -8,8 +9,51 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
 {
     public static class RazorExtensions
     {
+        public static void Register(RazorProjectEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            InjectDirective.Register(builder);
+            ModelDirective.Register(builder);
+            NamespaceDirective.Register(builder);
+            PageDirective.Register(builder);
+
+            FunctionsDirective.Register(builder);
+            InheritsDirective.Register(builder);
+            SectionDirective.Register(builder);
+
+            builder.AddTargetExtension(new ViewComponentTagHelperTargetExtension());
+            builder.AddTargetExtension(new TemplateTargetExtension()
+            {
+                TemplateTypeName = "global::Microsoft.AspNetCore.Mvc.Razor.HelperResult",
+            });
+
+            builder.Features.Add(new ModelExpressionPass());
+            builder.Features.Add(new PagesPropertyInjectionPass());
+            builder.Features.Add(new ViewComponentTagHelperPass());
+            builder.Features.Add(new RazorPageDocumentClassifierPass());
+            builder.Features.Add(new MvcViewDocumentClassifierPass());
+
+            if (!builder.DesignTime)
+            {
+                builder.Features.Add(new AssemblyAttributeInjectionPass());
+                builder.Features.Add(new InstrumentationPass());
+            }
+
+            builder.SetImportFeature(new DefaultMvcImportFeature());
+        }
+
+        #region Obsolete
         public static void Register(IRazorEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             InjectDirective.Register(builder);
             ModelDirective.Register(builder);
             NamespaceDirective.Register(builder);
@@ -37,5 +81,6 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
                 builder.Features.Add(new InstrumentationPass());
             }
         }
+        #endregion
     }
 }

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

@@ -6,10 +6,8 @@ using System.Collections.Generic;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
-    internal class DefaultRazorImportFeature : IRazorImportFeature
+    internal class DefaultRazorImportFeature : RazorProjectEngineFeatureBase, IRazorImportFeature
     {
-        public RazorProjectEngine ProjectEngine { get; set; }
-
         public IReadOnlyList<RazorSourceDocument> GetImports(string sourceFilePath) => Array.Empty<RazorSourceDocument>();
     }
 }

src/Microsoft.AspNetCore.Razor.Language/Extensions/FunctionsDirective.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Language.Extensions
@@ -15,10 +16,28 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 builder.Description = Resources.FunctionsDirective_Description;
             });
 
-        public static void Register(IRazorEngineBuilder builder)
+        public static void Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new FunctionsDirectivePass());
         }
+
+        #region Obsolete
+        public static void Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new FunctionsDirectivePass());
+        }
+        #endregion
     }
 }

src/Microsoft.AspNetCore.Razor.Language/Extensions/InheritsDirective.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Language.Extensions
@@ -17,10 +18,28 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 builder.Description = Resources.InheritsDirective_Description;
             });
 
-        public static void Register(IRazorEngineBuilder builder)
+        public static void Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new InheritsDirectivePass());
         }
+
+        #region Obsolete
+        public static void Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new InheritsDirectivePass());
+        }
+        #endregion
     }
 }

src/Microsoft.AspNetCore.Razor.Language/Extensions/SectionDirective.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Language.Extensions
@@ -16,11 +17,30 @@ namespace Microsoft.AspNetCore.Razor.Language.Extensions
                 builder.Description = Resources.SectionDirective_Description;
             });
 
-        public static void Register(IRazorEngineBuilder builder)
+        public static void Register(RazorProjectEngineBuilder builder)
         {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
             builder.AddDirective(Directive);
             builder.Features.Add(new SectionDirectivePass());
             builder.AddTargetExtension(new SectionTargetExtension());
         }
+
+        #region Obsolete
+        public static void Register(IRazorEngineBuilder builder)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            builder.AddDirective(Directive);
+            builder.Features.Add(new SectionDirectivePass());
+            builder.AddTargetExtension(new SectionTargetExtension());
+        }
+        #endregion
     }
 }

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Linq;
+using Microsoft.AspNetCore.Razor.Language.CodeGeneration;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
@@ -29,5 +30,77 @@ namespace Microsoft.AspNetCore.Razor.Language
 
             builder.Features.Add(feature);
         }
+
+        /// <summary>
+        /// Adds the specified <see cref="ICodeTargetExtension"/>.
+        /// </summary>
+        /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
+        /// <param name="extension">The <see cref="ICodeTargetExtension"/> to add.</param>
+        /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
+        public static RazorProjectEngineBuilder AddTargetExtension(this RazorProjectEngineBuilder builder, ICodeTargetExtension extension)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (extension == null)
+            {
+                throw new ArgumentNullException(nameof(extension));
+            }
+
+            var targetExtensionFeature = GetTargetExtensionFeature(builder);
+            targetExtensionFeature.TargetExtensions.Add(extension);
+
+            return builder;
+        }
+
+        /// <summary>
+        /// Adds the specified <see cref="DirectiveDescriptor"/>.
+        /// </summary>
+        /// <param name="builder">The <see cref="RazorProjectEngineBuilder"/>.</param>
+        /// <param name="directive">The <see cref="DirectiveDescriptor"/> to add.</param>
+        /// <returns>The <see cref="RazorProjectEngineBuilder"/>.</returns>
+        public static RazorProjectEngineBuilder AddDirective(this RazorProjectEngineBuilder builder, DirectiveDescriptor directive)
+        {
+            if (builder == null)
+            {
+                throw new ArgumentNullException(nameof(builder));
+            }
+
+            if (directive == null)
+            {
+                throw new ArgumentNullException(nameof(directive));
+            }
+
+            var directiveFeature = GetDirectiveFeature(builder);
+            directiveFeature.Directives.Add(directive);
+
+            return builder;
+        }
+
+        private static IRazorDirectiveFeature GetDirectiveFeature(RazorProjectEngineBuilder builder)
+        {
+            var directiveFeature = builder.Features.OfType<IRazorDirectiveFeature>().FirstOrDefault();
+            if (directiveFeature == null)
+            {
+                directiveFeature = new DefaultRazorDirectiveFeature();
+                builder.Features.Add(directiveFeature);
+            }
+
+            return directiveFeature;
+        }
+
+        private static IRazorTargetExtensionFeature GetTargetExtensionFeature(RazorProjectEngineBuilder builder)
+        {
+            var targetExtensionFeature = builder.Features.OfType<IRazorTargetExtensionFeature>().FirstOrDefault();
+            if (targetExtensionFeature == null)
+            {
+                targetExtensionFeature = new DefaultRazorTargetExtensionFeature();
+                builder.Features.Add(targetExtensionFeature);
+            }
+
+            return targetExtensionFeature;
+        }
     }
 }

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

@@ -0,0 +1,31 @@
+// 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;
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    public abstract class RazorProjectEngineFeatureBase : IRazorProjectEngineFeature
+    {
+        private RazorProjectEngine _projectEngine;
+
+        public RazorProjectEngine ProjectEngine
+        {
+            get => _projectEngine;
+            set
+            {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
+                _projectEngine = value;
+                OnInitialized();
+            }
+        }
+
+        protected virtual void OnInitialized()
+        {
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Test/DefaultMvcImportFeatureTest.cs

@@ -0,0 +1,77 @@
+// 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.Collections.Generic;
+using Microsoft.AspNetCore.Razor.Language;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
+{
+    public class DefaultMvcImportFeatureTest
+    {
+        [Fact]
+        public void AddDefaultDirectivesImport_AddsSingleDynamicImport()
+        {
+            // Arrange
+            var imports = new List<RazorSourceDocument>();
+
+            // Act
+            DefaultMvcImportFeature.AddDefaultDirectivesImport(imports);
+
+            // Assert
+            var import = Assert.Single(imports);
+            Assert.Null(import.FilePath);
+        }
+
+        [Fact]
+        public void AddHierarchicalImports_AddsViewImportSourceDocumentsOnDisk()
+        {
+            // Arrange
+            var imports = new List<RazorSourceDocument>();
+            var testFileSystem = new TestRazorProjectFileSystem(new[]
+            {
+                new TestRazorProjectItem("/Index.cshtml"),
+                new TestRazorProjectItem("/_ViewImports.cshtml"),
+                new TestRazorProjectItem("/Contact/_ViewImports.cshtml"),
+                new TestRazorProjectItem("/Contact/Index.cshtml"),
+            });
+            var mvcImportFeature = new DefaultMvcImportFeature()
+            {
+                ProjectEngine = Mock.Of<RazorProjectEngine>(projectEngine => projectEngine.FileSystem == testFileSystem)
+            };
+
+            // Act
+            mvcImportFeature.AddHierarchicalImports("/Contact/Index.cshtml", imports);
+
+            // Assert
+            Assert.Collection(imports,
+                import => Assert.Equal("/_ViewImports.cshtml", import.FilePath),
+                import => Assert.Equal("/Contact/_ViewImports.cshtml", import.FilePath));
+        }
+
+        [Fact]
+        public void AddHierarchicalImports_AddsViewImportSourceDocumentsNotOnDisk()
+        {
+            // Arrange
+            var imports = new List<RazorSourceDocument>();
+            var testFileSystem = new TestRazorProjectFileSystem(new[]
+            {
+                new TestRazorProjectItem("/Pages/Contact/Index.cshtml"),
+            });
+            var mvcImportFeature = new DefaultMvcImportFeature()
+            {
+                ProjectEngine = Mock.Of<RazorProjectEngine>(projectEngine => projectEngine.FileSystem == testFileSystem)
+            };
+
+            // Act
+            mvcImportFeature.AddHierarchicalImports("/Pages/Contact/Index.cshtml", imports);
+
+            // Assert
+            Assert.Collection(imports,
+                import => Assert.Equal("/_ViewImports.cshtml", import.FilePath),
+                import => Assert.Equal("/Pages/_ViewImports.cshtml", import.FilePath),
+                import => Assert.Equal("/Pages/Contact/_ViewImports.cshtml", import.FilePath));
+        }
+    }
+}

test/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X.Test/DefaultMvcImportFeatureTest.cs

@@ -0,0 +1,77 @@
+// 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.Collections.Generic;
+using Microsoft.AspNetCore.Razor.Language;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X
+{
+    public class DefaultMvcImportFeatureTest
+    {
+        [Fact]
+        public void AddDefaultDirectivesImport_AddsSingleDynamicImport()
+        {
+            // Arrange
+            var imports = new List<RazorSourceDocument>();
+
+            // Act
+            DefaultMvcImportFeature.AddDefaultDirectivesImport(imports);
+
+            // Assert
+            var import = Assert.Single(imports);
+            Assert.Null(import.FilePath);
+        }
+
+        [Fact]
+        public void AddHierarchicalImports_AddsViewImportSourceDocumentsOnDisk()
+        {
+            // Arrange
+            var imports = new List<RazorSourceDocument>();
+            var testFileSystem = new TestRazorProjectFileSystem(new[]
+            {
+                new TestRazorProjectItem("/Index.cshtml"),
+                new TestRazorProjectItem("/_ViewImports.cshtml"),
+                new TestRazorProjectItem("/Contact/_ViewImports.cshtml"),
+                new TestRazorProjectItem("/Contact/Index.cshtml"),
+            });
+            var mvcImportFeature = new DefaultMvcImportFeature()
+            {
+                ProjectEngine = Mock.Of<RazorProjectEngine>(projectEngine => projectEngine.FileSystem == testFileSystem)
+            };
+
+            // Act
+            mvcImportFeature.AddHierarchicalImports("/Contact/Index.cshtml", imports);
+
+            // Assert
+            Assert.Collection(imports,
+                import => Assert.Equal("/_ViewImports.cshtml", import.FilePath),
+                import => Assert.Equal("/Contact/_ViewImports.cshtml", import.FilePath));
+        }
+
+        [Fact]
+        public void AddHierarchicalImports_AddsViewImportSourceDocumentsNotOnDisk()
+        {
+            // Arrange
+            var imports = new List<RazorSourceDocument>();
+            var testFileSystem = new TestRazorProjectFileSystem(new[]
+            {
+                new TestRazorProjectItem("/Pages/Contact/Index.cshtml"),
+            });
+            var mvcImportFeature = new DefaultMvcImportFeature()
+            {
+                ProjectEngine = Mock.Of<RazorProjectEngine>(projectEngine => projectEngine.FileSystem == testFileSystem)
+            };
+
+            // Act
+            mvcImportFeature.AddHierarchicalImports("/Pages/Contact/Index.cshtml", imports);
+
+            // Assert
+            Assert.Collection(imports,
+                import => Assert.Equal("/_ViewImports.cshtml", import.FilePath),
+                import => Assert.Equal("/Pages/_ViewImports.cshtml", import.FilePath),
+                import => Assert.Equal("/Pages/Contact/_ViewImports.cshtml", import.FilePath));
+        }
+    }
+}

test/Microsoft.AspNetCore.Razor.Language.Test/RazorProjectEngineBuilderExtensionsTest.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using Microsoft.AspNetCore.Razor.Language.CodeGeneration;
 using Moq;
 using Xunit;
 
@@ -26,5 +27,77 @@ namespace Microsoft.AspNetCore.Razor.Language
             var feature = Assert.Single(builder.Features);
             Assert.Same(newFeature, feature);
         }
+
+        [Fact]
+        public void AddTargetExtension_CreatesAndAddsToTargetExtensionFeatureIfItDoesNotExist()
+        {
+            // Arrange
+            var builder = new DefaultRazorProjectEngineBuilder(false, Mock.Of<RazorProjectFileSystem>());
+            var expectedExtension = Mock.Of<ICodeTargetExtension>();
+
+            // Act
+            builder.AddTargetExtension(expectedExtension);
+
+            // Assert
+            var feature = Assert.Single(builder.Features);
+            var codeTargetExtensionFeature = Assert.IsAssignableFrom<IRazorTargetExtensionFeature>(feature);
+            var extensions = Assert.Single(codeTargetExtensionFeature.TargetExtensions);
+            Assert.Same(expectedExtension, extensions);
+        }
+
+        [Fact]
+        public void AddTargetExtension_UsesExistingFeatureIfExistsAndAddsTo()
+        {
+            // Arrange
+            var builder = new DefaultRazorProjectEngineBuilder(false, Mock.Of<RazorProjectFileSystem>());
+            var codeTargetExtensionFeature = new DefaultRazorTargetExtensionFeature();
+            builder.Features.Add(codeTargetExtensionFeature);
+            var expectedExtension = Mock.Of<ICodeTargetExtension>();
+
+            // Act
+            builder.AddTargetExtension(expectedExtension);
+
+            // Assert
+            var feature = Assert.Single(builder.Features);
+            Assert.Same(codeTargetExtensionFeature, feature);
+            var extensions = Assert.Single(codeTargetExtensionFeature.TargetExtensions);
+            Assert.Same(expectedExtension, extensions);
+        }
+
+        [Fact]
+        public void AddDirective_CreatesAndAddsToDirectiveFeatureIfItDoesNotExist()
+        {
+            // Arrange
+            var builder = new DefaultRazorProjectEngineBuilder(false, Mock.Of<RazorProjectFileSystem>());
+            var expectedDirective = Mock.Of<DirectiveDescriptor>();
+
+            // Act
+            builder.AddDirective(expectedDirective);
+
+            // Assert
+            var feature = Assert.Single(builder.Features);
+            var directiveFeature = Assert.IsAssignableFrom<IRazorDirectiveFeature>(feature);
+            var directive = Assert.Single(directiveFeature.Directives);
+            Assert.Same(expectedDirective, directive);
+        }
+
+        [Fact]
+        public void AddDirective_UsesExistingFeatureIfExistsAndAddsTo()
+        {
+            // Arrange
+            var builder = new DefaultRazorProjectEngineBuilder(false, Mock.Of<RazorProjectFileSystem>());
+            var directiveFeature = new DefaultRazorDirectiveFeature();
+            builder.Features.Add(directiveFeature);
+            var expecteDirective = Mock.Of<DirectiveDescriptor>();
+
+            // Act
+            builder.AddDirective(expecteDirective);
+
+            // Assert
+            var feature = Assert.Single(builder.Features);
+            Assert.Same(directiveFeature, feature);
+            var directive = Assert.Single(directiveFeature.Directives);
+            Assert.Same(expecteDirective, directive);
+        }
     }
 }

test/Microsoft.AspNetCore.Razor.Language.Test/RazorProjectEngineFeatureBaseTest.cs

@@ -0,0 +1,34 @@
+// 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 Moq;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    public class RazorProjectEngineFeatureBaseTest
+    {
+        [Fact]
+        public void ProjectEngineSetter_CallsOnInitialized()
+        {
+            // Arrange
+            var testFeature = new TestFeature();
+
+            // Act
+            testFeature.ProjectEngine = Mock.Of<RazorProjectEngine>();
+
+            // Assert
+            Assert.Equal(1, testFeature.InitializationCount);
+        }
+
+        private class TestFeature : RazorProjectEngineFeatureBase
+        {
+            public int InitializationCount { get; private set; }
+
+            protected override void OnInitialized()
+            {
+                InitializationCount++;
+            }
+        }
+    }
+}