Changes to support PageExecutionContext in Razor

Fixes #1083

src/Microsoft.AspNet.Mvc.Razor.Host/IMvcRazorHost.cs

@@ -6,8 +6,24 @@ using Microsoft.AspNet.Razor;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
+    /// <summary>
+    /// Specifies the contracts for a Razor host that parses Razor files and generates C# code.
+    /// </summary>
     public interface IMvcRazorHost
     {
+        /// <summary>
+        /// Flag that indicates if page execution instrumentation code should be injected into the output.
+        /// </summary>
+        bool EnableInstrumentation { get; set; }
+
+        /// <summary>
+        /// Parses and generates the contents of a Razor file represented by <paramref name="inputStream"/>.
+        /// </summary>
+        /// <param name="rootRelativePath">The path of the relative to the root of the application. 
+        /// Used to generate line pragmas and calculate the class name of the generated type.</param>
+        /// <param name="inputStream">A <see cref="Stream"/> that represents the Razor contents.</param>
+        /// <returns>A <see cref="GeneratorResults"/> instance that represents the results of code generation.
+        /// </returns>
         GeneratorResults GenerateCode(string rootRelativePath, Stream inputStream);
 
         /// <summary>

src/Microsoft.AspNet.Mvc.Razor.Host/MvcRazorHost.cs

@@ -82,7 +82,9 @@ namespace Microsoft.AspNet.Mvc.Razor
                 templateTypeName: "Microsoft.AspNet.Mvc.Razor.HelperResult",
                 defineSectionMethodName: "DefineSection")
             {
-                ResolveUrlMethodName = "Href"
+                ResolveUrlMethodName = "Href",
+                BeginContextMethodName = "BeginContext",
+                EndContextMethodName = "EndContext"
             };
 
             foreach (var ns in _defaultNamespaces)

src/Microsoft.AspNet.Mvc.Razor/IRazorPage.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 
 namespace Microsoft.AspNet.Mvc.Razor
 {
@@ -44,6 +45,11 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// </summary>
         string Layout { get; set; }
 
+        /// <summary>
+        /// Gets or sets a <see cref="IPageExecutionContext"/> instance used to instrument the page execution.
+        /// </summary>
+        IPageExecutionContext PageExecutionContext { get; set; }
+
         /// <summary>
         /// Gets or sets the sections that can be rendered by this page.
         /// </summary>

src/Microsoft.AspNet.Mvc.Razor/Properties/Resources.Designer.cs

@@ -58,6 +58,22 @@ namespace Microsoft.AspNet.Mvc.Razor
             return string.Format(CultureInfo.CurrentCulture, GetString("FlushPointCannotBeInvoked"), p0);
         }
 
+        /// <summary>
+        /// The {0} returned by '{1}' must be an instance of '{2}'.
+        /// </summary>
+        internal static string Instrumentation_WriterMustBeBufferedTextWriter
+        {
+            get { return GetString("Instrumentation_WriterMustBeBufferedTextWriter"); }
+        }
+
+        /// <summary>
+        /// The {0} returned by '{1}' must be an instance of '{2}'.
+        /// </summary>
+        internal static string FormatInstrumentation_WriterMustBeBufferedTextWriter(object p0, object p1, object p2)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("Instrumentation_WriterMustBeBufferedTextWriter"), p0, p1, p2);
+        }
+
         /// <summary>
         /// The layout view '{0}' could not be located.
         /// </summary>

src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs

@@ -10,6 +10,7 @@ using System.Security.Principal;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 using Microsoft.Framework.DependencyInjection;
 
 namespace Microsoft.AspNet.Mvc.Razor
@@ -47,8 +48,12 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// <inheritdoc />
         public ViewContext ViewContext { get; set; }
 
+        /// <inheritdoc />
         public string Layout { get; set; }
 
+        /// <inheritdoc />
+        public IPageExecutionContext PageExecutionContext { get; set; }
+
         /// <summary>
         /// Gets the TextWriter that the page is writing output to.
         /// </summary>
@@ -268,6 +273,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                     // Calculate length of the source span by the position of the next value (or suffix)
                     var sourceLength = next.Position - attrVal.Value.Position;
 
+                    BeginContext(attrVal.Value.Position, sourceLength, isLiteral: attrVal.Literal);
                     // The extra branching here is to ensure that we call the Write*To(string) overload whe
                     // possible.
                     if (attrVal.Literal && stringValue != null)
@@ -287,6 +293,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                         WriteTo(writer, val.Value);
                     }
 
+                    EndContext();
                     wroteSomething = true;
                 }
                 if (wroteSomething)
@@ -308,7 +315,9 @@ namespace Microsoft.AspNet.Mvc.Razor
 
         private void WritePositionTaggedLiteral(TextWriter writer, string value, int position)
         {
+            BeginContext(position, value.Length, isLiteral: true);
             WriteLiteralTo(writer, value);
+            EndContext();
         }
 
         private void WritePositionTaggedLiteral(TextWriter writer, PositionTagged<string> value)
@@ -420,6 +429,16 @@ namespace Microsoft.AspNet.Mvc.Razor
             }
         }
 
+        public void BeginContext(int position, int length, bool isLiteral)
+        {
+            PageExecutionContext?.BeginContext(position, length, isLiteral);
+        }
+
+        public void EndContext()
+        {
+            PageExecutionContext?.EndContext();
+        }
+
         private void EnsureMethodCanBeInvoked(string methodName)
         {
             if (PreviousSectionWriters == null)

src/Microsoft.AspNet.Mvc.Razor/RazorTextWriter.cs

@@ -18,7 +18,7 @@ namespace Microsoft.AspNet.Mvc.Razor
     /// This is primarily designed to avoid creating large in-memory strings.
     /// Refer to https://aspnetwebstack.codeplex.com/workitem/585 for more details.
     /// </remarks>
-    public class RazorTextWriter : TextWriter
+    public class RazorTextWriter : TextWriter, IBufferedTextWriter
     {
         private static readonly Task _completedTask = Task.FromResult(0);
         private readonly TextWriter _unbufferedWriter;
@@ -43,9 +43,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             get { return _encoding; }
         }
 
-        /// <summary>
+        /// <inheritdoc />
-        /// Gets a flag that determines if this instance of <see cref="RazorTextWriter"/> is buffering content.
-        /// </summary>
         public bool IsBuffering { get; private set; } = true;
 
         /// <summary>
@@ -267,10 +265,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             await _unbufferedWriter.FlushAsync();
         }
 
-        /// <summary>
+        /// <inheritdoc />
-        /// Copies the content of the <see cref="RazorTextWriter"/> to the <see cref="TextWriter"/> instance.
-        /// </summary>
-        /// <param name="writer">The writer to copy contents to.</param>
         public void CopyTo(TextWriter writer)
         {
             var targetRazorTextWriter = writer as RazorTextWriter;
@@ -286,11 +281,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             }
         }
 
-        /// <summary>
+        /// <inheritdoc />
-        /// Copies the content of the <see cref="RazorTextWriter"/> to the specified <see cref="TextWriter"/> instance.
-        /// </summary>
-        /// <param name="writer">The writer to copy contents to.</param>
-        /// <returns>A task that represents the asynchronous copy operation.</returns>
         public Task CopyToAsync(TextWriter writer)
         {
             var targetRazorTextWriter = writer as RazorTextWriter;

src/Microsoft.AspNet.Mvc.Razor/Resources.resx

@@ -126,6 +126,9 @@
   <data name="FlushPointCannotBeInvoked" xml:space="preserve">
     <value>'{0}' cannot be invoked when a Layout page is set to be executed.</value>
   </data>
+  <data name="Instrumentation_WriterMustBeBufferedTextWriter" xml:space="preserve">
+    <value>The {0} returned by '{1}' must be an instance of '{2}'.</value>
+  </data>
   <data name="LayoutCannotBeLocated" xml:space="preserve">
     <value>The layout view '{0}' could not be located.</value>
   </data>

src/Microsoft.AspNet.Mvc.Razor/Services/IBufferedTextWriter.cs

@@ -0,0 +1,34 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.IO;
+using System.Threading.Tasks;
+using Microsoft.Framework.Runtime;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    /// <summary>
+    /// Specifies the contracts for a <see cref="TextWriter"/> that buffers its content.
+    /// </summary>
+    [AssemblyNeutral]
+    public interface IBufferedTextWriter
+    {
+        /// <summary>
+        /// Gets a flag that determines if content is currently being buffered.
+        /// </summary>
+        bool IsBuffering { get; }
+
+        /// <summary>
+        /// Copies the buffered content to the <paramref name="writer"/>.
+        /// </summary>
+        /// <param name="writer">The writer to copy the contents to./param>
+        void CopyTo(TextWriter writer);
+
+        /// <summary>
+        /// Asynchronously copies the buffered content to the <paramref name="writer"/>.
+        /// </summary>
+        /// <param name="writer">The writer to copy the contents to./param>
+        /// <returns>A <see cref="Task"/> representing the copy operation.</returns>
+        Task CopyToAsync(TextWriter writer);
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/Services/IPageExecutionContext.cs

@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.Framework.Runtime;
+
+namespace Microsoft.AspNet.PageExecutionInstrumentation
+{
+    /// <summary>
+    /// Specifies the contracts for a execution context that instruments web page execution.
+    /// </summary>
+    [AssemblyNeutral]
+    public interface IPageExecutionContext
+    {
+        /// <summary>
+        /// Invoked at the start of a write operation.
+        /// </summary>
+        /// <param name="position">The absolute character position of the expression or text in the Razor file.</param>
+        /// <param name="length">The character length of the expression or text in the Razor file.</param>
+        /// <param name="isLiteral">A flag that indicates if the operation is for a literal text and not for a
+        /// language expression.</param>
+        void BeginContext(int position, int length, bool isLiteral);
+
+        /// <summary>
+        /// Invoked at the end of a write operation.
+        /// </summary>
+        void EndContext();
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/Services/IPageExecutionListenerFeature.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.IO;
+using Microsoft.Framework.Runtime;
+
+namespace Microsoft.AspNet.PageExecutionInstrumentation
+{
+    /// <summary>
+    /// Specifies the contracts for a HTTP feature that provides the context to instrument a web page.
+    /// </summary>
+    [AssemblyNeutral]
+    public interface IPageExecutionListenerFeature
+    {
+        /// <summary>
+        /// Decorates the <see cref="TextWriter"/> used by web page instances to
+        /// write the result to.
+        /// </summary>
+        /// <param name="writer">The output <see cref="TextWriter"/> for the web page.</param>
+        /// <returns>A <see cref="TextWriter"/> that wraps <paramref name="writer"/>.</returns>
+        /// <remarks>
+        TextWriter DecorateWriter(TextWriter writer);
+
+        /// <summary>
+        /// Creates a <see cref="IPageExecutionContext"/> for the specified <paramref name="sourceFilePath"/>.
+        /// </summary>
+        /// <param name="sourceFilePath">The path of the <see cref="Mvc.Razor.IRazorPage"/>.</param>
+        /// <param name="writer">The <see cref="TextWriter"/> obtained from <see cref="DecorateWriter(TextWriter)"/>.
+        /// </param>
+        /// <returns></returns>
+        IPageExecutionContext GetContext(string sourceFilePath, TextWriter writer);
+    }
+}

test/Microsoft.AspNet.Mvc.Razor.Host.Test/InjectChunkVisitorTest.cs

@@ -2,14 +2,10 @@
 // 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 Microsoft.AspNet.Razor;
 using Microsoft.AspNet.Razor.Generator;
 using Microsoft.AspNet.Razor.Generator.Compiler;
 using Microsoft.AspNet.Razor.Generator.Compiler.CSharp;
 using Microsoft.AspNet.Razor.Parser.SyntaxTree;
-using Microsoft.AspNet.Razor.Text;
 using Xunit;
 
 namespace Microsoft.AspNet.Mvc.Razor

test/Microsoft.AspNet.Mvc.Razor.Test/RazorPageTest.cs

@@ -5,8 +5,8 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Threading.Tasks;
-using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Mvc.Rendering;
+using Microsoft.AspNet.PageExecutionInstrumentation;
 using Microsoft.AspNet.PipelineCore;
 using Microsoft.AspNet.Testing;
 using Moq;
@@ -351,6 +351,68 @@ Layout end
             Assert.DoesNotThrow(() => page.SectionWriters["test-section"].WriteTo(TextWriter.Null));
         }
 
+        [Fact]
+        public async Task WriteAttribute_CallsBeginAndEndContext_OnPageExecutionListenerContext()
+        {
+            // Arrange
+            var page = CreatePage(p =>
+            {
+                p.WriteAttribute("href",
+                                 new PositionTagged<string>("prefix", 0),
+                                 new PositionTagged<string>("suffix", 34),
+                                 new AttributeValue(new PositionTagged<string>("prefix", 0),
+                                                    new PositionTagged<object>("attr1-value", 8),
+                                                    literal: true),
+                                 new AttributeValue(new PositionTagged<string>("prefix2", 22),
+                                                    new PositionTagged<object>("attr2", 29),
+                                                    literal: false));
+            });
+            var context = new Mock<IPageExecutionContext>(MockBehavior.Strict);
+            var sequence = new MockSequence();
+            context.InSequence(sequence).Setup(f => f.BeginContext(0, 6, true)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            context.InSequence(sequence).Setup(f => f.BeginContext(8, 14, true)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            context.InSequence(sequence).Setup(f => f.BeginContext(22, 7, true)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            context.InSequence(sequence).Setup(f => f.BeginContext(29, 5, false)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            context.InSequence(sequence).Setup(f => f.BeginContext(34, 6, true)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            page.PageExecutionContext = context.Object;
+
+            // Act
+            await page.ExecuteAsync();
+
+            // Assert
+            context.Verify();
+        }
+
+        [Fact]
+        public async Task WriteAttribute_CallsBeginAndEndContext_OnPrefixAndSuffixValues()
+        {
+            // Arrange
+            var page = CreatePage(p =>
+            {
+                p.WriteAttribute("href",
+                                 new PositionTagged<string>("prefix", 0),
+                                 new PositionTagged<string>("tail", 7));
+            });
+            var context = new Mock<IPageExecutionContext>(MockBehavior.Strict);
+            var sequence = new MockSequence();
+            context.InSequence(sequence).Setup(f => f.BeginContext(0, 6, true)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            context.InSequence(sequence).Setup(f => f.BeginContext(7, 4, true)).Verifiable();
+            context.InSequence(sequence).Setup(f => f.EndContext()).Verifiable();
+            page.PageExecutionContext = context.Object;
+
+            // Act
+            await page.ExecuteAsync();
+
+            // Assert
+            context.Verify();
+        }
+
         private static TestableRazorPage CreatePage(Action<TestableRazorPage> executeAction,
                                                     ViewContext context = null)
         {