Add an option to RazorPrecompileModule to allow conditional compilation

based on Configuration.

Fixes #3276

samples/TagHelperSample.Web/compiler/preprocess/RazorPreCompilation.cs

@@ -0,0 +1,12 @@
+// 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.AspNet.Mvc.Razor.Precompilation;
+
+namespace TagHelperSample.Web
+{
+    public class TagHelpersRazorPreCompilation : RazorPreCompileModule
+    {
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/Precompilation/RazorPreCompileModule.cs

@@ -16,6 +16,7 @@ namespace Microsoft.AspNet.Mvc.Razor.Precompilation
     /// </summary>
     public abstract class RazorPreCompileModule : ICompileModule
     {
+        private const string ReleaseConfiguration = "release";
         private readonly object _memoryCacheLookupLock = new object();
         private readonly Dictionary<PrecompilationCacheKey, MemoryCache> _memoryCacheLookup =
             new Dictionary<PrecompilationCacheKey, MemoryCache>();
@@ -29,6 +30,11 @@ namespace Microsoft.AspNet.Mvc.Razor.Precompilation
         /// <remarks>Pre-compiles all Razor views in the application.</remarks>
         public virtual void BeforeCompile(BeforeCompileContext context)
         {
+            if (!EnablePreCompilation(context))
+            {
+                return;
+            }
+
             var fileProvider = new PhysicalFileProvider(context.ProjectContext.ProjectDirectory);
 
             MemoryCache memoryCache;
@@ -67,6 +73,27 @@ namespace Microsoft.AspNet.Mvc.Razor.Precompilation
         {
         }
 
+        /// <summary>
+        /// Determines if this instance of <see cref="RazorPreCompileModule"/> should enable
+        /// compilation of views.
+        /// </summary>
+        /// <param name="context">The <see cref="BeforeCompileContext"/>.</param>
+        /// <returns><c>true</c> if views should be precompiled; otherwise <c>false</c>.</returns>
+        /// <remarks>Returns <c>true</c> if the current application is being built in <c>release</c>
+        /// configuration.</remarks>
+        protected virtual bool EnablePreCompilation(BeforeCompileContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            return string.Equals(
+                context.ProjectContext.Configuration,
+                ReleaseConfiguration,
+                StringComparison.OrdinalIgnoreCase);
+        }
+
         private class PrecompilationCacheKey : IEquatable<PrecompilationCacheKey>
         {
             public string Configuration { get; set; }

test/WebSites/PrecompilationWebSite/compiler/preprocess/RazorPreCompilation.cs

@@ -1,15 +1,13 @@
 // 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.AspNet.Mvc.Razor.Precompilation;
+using Microsoft.Dnx.Compilation.CSharp;
 
 namespace PrecompilationWebSite
 {
     public class RazorPreCompilation : RazorPreCompileModule
     {
-        public RazorPreCompilation()
+        protected override bool EnablePreCompilation(BeforeCompileContext context) => true;
-        {
-        }
     }
 }