[Design] Add DiagnosticSource to RazorView

src/Microsoft.AspNetCore.Mvc.Razor/Internal/MvcRazorDiagnosticSourceExtensions.cs

@@ -0,0 +1,49 @@
+// 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.Diagnostics;
+using Microsoft.AspNetCore.Mvc.Rendering;
+
+namespace Microsoft.AspNetCore.Mvc.Razor.Internal
+{
+    public static class MvcRazorDiagnosticSourceExtensions
+    {
+        public static void BeforeViewPage(
+            this DiagnosticSource diagnosticSource,
+            IRazorPage page,
+            ViewContext viewContext)
+        {
+            if (diagnosticSource.IsEnabled("Microsoft.AspNetCore.Mvc.Razor.BeforeViewPage"))
+            {
+                diagnosticSource.Write(
+                    "Microsoft.AspNetCore.Mvc.Razor.BeforeViewPage",
+                    new
+                    {
+                        page = page,
+                        viewContext = viewContext,
+                        actionDescriptor = viewContext.ActionDescriptor,
+                        httpContext = viewContext.HttpContext,
+                    });
+            }
+        }
+
+        public static void AfterViewPage(
+            this DiagnosticSource diagnosticSource,
+            IRazorPage page,
+            ViewContext viewContext)
+        {
+            if (diagnosticSource.IsEnabled("Microsoft.AspNetCore.Mvc.Razor.AfterViewPage"))
+            {
+                diagnosticSource.Write(
+                    "Microsoft.AspNetCore.Mvc.Razor.AfterViewPage",
+                    new
+                    {
+                        page = page,
+                        viewContext = viewContext,
+                        actionDescriptor = viewContext.ActionDescriptor,
+                        httpContext = viewContext.HttpContext,
+                    });
+            }
+        }
+    }
+}

src/Microsoft.AspNetCore.Mvc.Razor/RazorView.cs

@@ -10,6 +10,7 @@
 using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.AspNetCore.Mvc.ViewEngines;
 using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;
+using Microsoft.AspNetCore.Mvc.Razor.Internal;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Mvc.Razor
@@ -23,6 +24,7 @@ public class RazorView : IView
         private readonly IRazorViewEngine _viewEngine;
         private readonly IRazorPageActivator _pageActivator;
         private readonly HtmlEncoder _htmlEncoder;
+        private readonly DiagnosticSource _diagnosticSource;
         private IViewBufferScope _bufferScope;
 
         /// <summary>
@@ -34,12 +36,14 @@ public class RazorView : IView
         /// </param>
         /// <param name="razorPage">The <see cref="IRazorPage"/> instance to execute.</param>
         /// <param name="htmlEncoder">The HTML encoder.</param>
+        /// <param name="diagnosticSource">The <see cref="DiagnosticSource"/>.</param>
         public RazorView(
             IRazorViewEngine viewEngine,
             IRazorPageActivator pageActivator,
             IReadOnlyList<IRazorPage> viewStartPages,
             IRazorPage razorPage,
-            HtmlEncoder htmlEncoder)
+            HtmlEncoder htmlEncoder,
+            DiagnosticSource diagnosticSource)
         {
             if (viewEngine == null)
             {
@@ -66,11 +70,17 @@ public RazorView(
                 throw new ArgumentNullException(nameof(htmlEncoder));
             }
 
+            if (diagnosticSource == null)
+            {
+                throw new ArgumentNullException(nameof(diagnosticSource));
+            }
+
             _viewEngine = viewEngine;
             _pageActivator = pageActivator;
             ViewStartPages = viewStartPages;
             RazorPage = razorPage;
             _htmlEncoder = htmlEncoder;
+            _diagnosticSource = diagnosticSource;
         }
 
         /// <inheritdoc />
@@ -152,11 +162,21 @@ private async Task<ViewBufferTextWriter> RenderPageAsync(
             }
         }
 
-        private Task RenderPageCoreAsync(IRazorPage page, ViewContext context)
+        private async Task RenderPageCoreAsync(IRazorPage page, ViewContext context)
         {
             page.ViewContext = context;
             _pageActivator.Activate(page, context);
-            return page.ExecuteAsync();
+
+            _diagnosticSource.BeforeViewPage(page, context);
+
+            try
+            {
+                await page.ExecuteAsync();
+            }
+            finally
+            {
+                _diagnosticSource.AfterViewPage(page, context);
+            }
         }
 
         private async Task RenderViewStartsAsync(ViewContext context)

src/Microsoft.AspNetCore.Mvc.Razor/RazorViewEngine.cs

@@ -44,6 +44,7 @@ public class RazorViewEngine : IRazorViewEngine
         private readonly ILogger _logger;
         private readonly RazorViewEngineOptions _options;
         private readonly RazorProject _razorProject;
+        private readonly DiagnosticSource _diagnosticSource;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RazorViewEngine" />.
@@ -54,7 +55,8 @@ public RazorViewEngine(
             HtmlEncoder htmlEncoder,
             IOptions<RazorViewEngineOptions> optionsAccessor,
             RazorProject razorProject,
-            ILoggerFactory loggerFactory)
+            ILoggerFactory loggerFactory,
+            DiagnosticSource diagnosticSource)
         {
             _options = optionsAccessor.Value;
 
@@ -77,6 +79,7 @@ public RazorViewEngine(
             _htmlEncoder = htmlEncoder;
             _logger = loggerFactory.CreateLogger<RazorViewEngine>();
             _razorProject = razorProject;
+            _diagnosticSource = diagnosticSource;
             ViewLookupCache = new MemoryCache(new MemoryCacheOptions());
         }
 
@@ -466,7 +469,7 @@ private ViewEngineResult CreateViewEngineResult(ViewLocationCacheResult result,
                 viewStarts[i] = viewStartItem.PageFactory();
             }
 
-            var view = new RazorView(this, _pageActivator, viewStarts, page, _htmlEncoder);
+            var view = new RazorView(this, _pageActivator, viewStarts, page, _htmlEncoder, _diagnosticSource);
             return ViewEngineResult.Found(viewName, view);
         }
 

src/Microsoft.AspNetCore.Mvc.RazorPages/Infrastructure/PageResultExecutor.cs

@@ -19,6 +19,7 @@ public class PageResultExecutor : ViewExecutor
     {
         private readonly IRazorViewEngine _razorViewEngine;
         private readonly IRazorPageActivator _razorPageActivator;
+        private readonly DiagnosticSource _diagnosticSource;
         private readonly HtmlEncoder _htmlEncoder;
 
         /// <summary>
@@ -42,6 +43,7 @@ public PageResultExecutor(
             _razorViewEngine = razorViewEngine;
             _htmlEncoder = htmlEncoder;
             _razorPageActivator = razorPageActivator;
+            _diagnosticSource = diagnosticSource;
         }
 
         /// <summary>
@@ -76,7 +78,8 @@ public virtual Task ExecuteAsync(PageContext pageContext, PageResult result)
                 _razorPageActivator,
                 viewStarts,
                 new RazorPageAdapter(result.Page),
-                _htmlEncoder);
+                _htmlEncoder,
+                _diagnosticSource);
 
             return ExecuteAsync(viewContext, result.ContentType, result.StatusCode);
         }

test/Microsoft.AspNetCore.Mvc.Razor.Test/RazorViewEngineTest.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
@@ -1350,7 +1351,8 @@ public void CreateCacheResult_LogsPrecompiledViewFound()
                 new HtmlTestEncoder(),
                 GetOptionsAccessor(expanders: null),
                 new FileProviderRazorProject(new TestFileProvider()),
-                loggerFactory);
+                loggerFactory,
+                new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"));
 
             // Act
             var result = viewEngine.CreateCacheResult(null, relativePath, false);
@@ -1881,7 +1883,7 @@ public TestableRazorViewEngine(
                 IRazorPageFactoryProvider pageFactory,
                 IOptions<RazorViewEngineOptions> optionsAccessor,
                 RazorProject razorProject)
-                : base(pageFactory, Mock.Of<IRazorPageActivator>(), new HtmlTestEncoder(), optionsAccessor, razorProject, NullLoggerFactory.Instance)
+                : base(pageFactory, Mock.Of<IRazorPageActivator>(), new HtmlTestEncoder(), optionsAccessor, razorProject, NullLoggerFactory.Instance, new DiagnosticListener("Microsoft.AspNetCore.Mvc.Razor"))
             {
             }