Make RazorViewEngineOptions.FileProvider a list instead of a single item

Fixes #3806

samples/EmbeddedViewSample.Web/Startup.cs

@@ -20,10 +20,12 @@ public void ConfigureServices(IServiceCollection services)
 
             services.Configure<RazorViewEngineOptions>(options =>
             {
+                options.FileProviders.Clear();
+
                 // Base namespace matches the resources added to the assembly from the EmbeddedResources folder.
-                options.FileProvider = new EmbeddedFileProvider(
+                options.FileProviders.Add(new EmbeddedFileProvider(
                     GetType().GetTypeInfo().Assembly,
-                    baseNamespace: "EmbeddedViewSample.Web.EmbeddedResources");
+                    baseNamespace: "EmbeddedViewSample.Web.EmbeddedResources"));
             });
         }
 

src/Microsoft.AspNet.Mvc.Razor/Compilation/DefaultCompilerCacheProvider.cs

@@ -16,7 +16,7 @@ public class DefaultCompilerCacheProvider : ICompilerCacheProvider
         /// <param name="optionsAccessor">An accessor to the <see cref="RazorViewEngineOptions"/>.</param>
         public DefaultCompilerCacheProvider(IOptions<RazorViewEngineOptions> mvcViewOptions)
         {
-            var fileProvider = mvcViewOptions.Value.FileProvider;
+            var fileProvider = mvcViewOptions.Value.GetCompositeFileProvider();
             Cache = new CompilerCache(fileProvider);
         }
 

src/Microsoft.AspNet.Mvc.Razor/Compilation/PrecompiledViewsCompilerCacheProvider.cs

@@ -42,7 +42,7 @@ public PrecompiledViewsCompilerCacheProvider(
             IEnumerable<Assembly> assemblies)
         {
             _loadContextAccessor = loadContextAccessor;
-            _fileProvider = mvcViewOptions.Value.FileProvider;
+            _fileProvider = mvcViewOptions.Value.GetCompositeFileProvider();
             _createCache = CreateCache;
             _assemblies = assemblies.ToArray();
         }

src/Microsoft.AspNet.Mvc.Razor/Compilation/RazorCompilationService.cs

@@ -27,17 +27,15 @@ public class RazorCompilationService : IRazorCompilationService
         /// </summary>
         /// <param name="compilationService">The <see cref="ICompilationService"/> to compile generated code.</param>
         /// <param name="razorHost">The <see cref="IMvcRazorHost"/> to generate code from Razor files.</param>
-        /// <param name="viewEngineOptions">
-        /// The <see cref="IFileProvider"/> to read Razor files referenced in error messages.
-        /// </param>
+        /// <param name="viewEngineOptions">Accessor to <see cref="RazorViewEngineOptions"/>.</param>
         public RazorCompilationService(
             ICompilationService compilationService,
             IMvcRazorHost razorHost,
             IOptions<RazorViewEngineOptions> viewEngineOptions)
         {
             _compilationService = compilationService;
             _razorHost = razorHost;
-            _fileProvider = viewEngineOptions.Value.FileProvider;
+            _fileProvider = viewEngineOptions.Value.GetCompositeFileProvider();
         }
 
         /// <inheritdoc />
@@ -105,9 +103,10 @@ internal CompilationResult GetCompilationFailedResult(RelativeFileInfo file, IEn
 
         private DiagnosticMessage CreateDiagnosticMessage(RazorError error, string filePath)
         {
+            var location = error.Location;
             return new DiagnosticMessage(
                 message: error.Message,
-                formattedMessage: $"{error} ({error.Location.LineIndex},{error.Location.CharacterIndex}) {error.Message}",
+                formattedMessage: $"{error} ({location.LineIndex},{location.CharacterIndex}) {error.Message}",
                 filePath: filePath,
                 startLine: error.Location.LineIndex + 1,
                 startColumn: error.Location.CharacterIndex,

src/Microsoft.AspNet.Mvc.Razor/Compilation/RoslynCompilationService.cs

@@ -65,7 +65,7 @@ public RoslynCompilationService(
             _environment = environment;
             _libraryExporter = libraryExporter;
             _applicationReferences = new Lazy<List<MetadataReference>>(GetApplicationReferences);
-            _fileProvider = optionsAccessor.Value.FileProvider;
+            _fileProvider = optionsAccessor.Value.GetCompositeFileProvider();
             _classPrefix = host.MainClassNamePrefix;
             _compilationCallback = optionsAccessor.Value.CompilationCallback;
             _parseOptions = optionsAccessor.Value.ParseOptions;

src/Microsoft.AspNet.Mvc.Razor/DependencyInjection/MvcRazorMvcCoreBuilderExtensions.cs

@@ -14,7 +14,6 @@
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.CompilationAbstractions;
 using Microsoft.Extensions.DependencyInjection.Extensions;
-using Microsoft.Extensions.MemoryPool;
 using Microsoft.Extensions.Options;
 using Microsoft.Extensions.PlatformAbstractions;
 
@@ -134,8 +133,8 @@ internal static void AddRazorViewEngineServices(IServiceCollection services)
 
             services.TryAdd(ServiceDescriptor.Singleton<IChunkTreeCache>(serviceProvider =>
             {
-                var cachedFileProvider = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
-                return new DefaultChunkTreeCache(cachedFileProvider.Value.FileProvider);
+                var viewEngineOptions = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
+                return new DefaultChunkTreeCache(viewEngineOptions.Value.GetCompositeFileProvider());
             }));
 
             // Caches compilation artifacts across the lifetime of the application.

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

@@ -14,13 +14,13 @@ namespace Microsoft.AspNet.Mvc.Razor
     /// </summary>
     public class RazorViewEngineOptions
     {
-        private IFileProvider _fileProvider;
-
         private CSharpParseOptions _parseOptions = new CSharpParseOptions(LanguageVersion.CSharp6);
 
-        private CSharpCompilationOptions _compilationOptions = new CSharpCompilationOptions(CodeAnalysis.OutputKind.DynamicallyLinkedLibrary);
+        private CSharpCompilationOptions _compilationOptions =
+            new CSharpCompilationOptions(CodeAnalysis.OutputKind.DynamicallyLinkedLibrary);
 
         private Action<RoslynCompilationContext> _compilationCallback = c => { };
+        private IFileProvider _fileProvider;
 
         /// <summary>
         /// Get a <see cref="IList{IViewLocationExpander}"/> used by the <see cref="RazorViewEngine"/>.
@@ -29,33 +29,22 @@ public class RazorViewEngineOptions
             = new List<IViewLocationExpander>();
 
         /// <summary>
-        /// Gets or sets the <see cref="IFileProvider" /> used by <see cref="RazorViewEngine"/> to locate Razor files on
-        /// disk.
+        /// Gets the sequence of <see cref="IFileProvider" /> instances used by <see cref="RazorViewEngine"/> to
+        /// locate Razor files.
         /// </summary>
         /// <remarks>
-        /// At startup, this is initialized to an instance of <see cref="PhysicalFileProvider"/> that is rooted at the
-        /// application root.
+        /// At startup, this is initialized to include an instance of <see cref="PhysicalFileProvider"/> that is
+        /// rooted at the application root.
         /// </remarks>
-        public IFileProvider FileProvider
-        {
-            get { return _fileProvider; }
-
-            set
-            {
-                if (value == null)
-                {
-                    throw new ArgumentNullException(nameof(value));
-                }
-
-                _fileProvider = value;
-            }
-        }
+        public IList<IFileProvider> FileProviders { get; } = new List<IFileProvider>();
 
         /// <summary>
         /// Gets or sets the callback that is used to customize Razor compilation
         /// to change compilation settings you can update <see cref="RoslynCompilationContext.Compilation"/> property.
-        /// Customizations made here would not reflect in tooling (Intellisense).
         /// </summary>
+        /// <remarks>
+        /// Customizations made here would not reflect in tooling (Intellisense).
+        /// </remarks>
         public Action<RoslynCompilationContext> CompilationCallback
         {
             get { return _compilationCallback; }
@@ -65,6 +54,7 @@ public Action<RoslynCompilationContext> CompilationCallback
                 {
                     throw new ArgumentNullException(nameof(value));
                 }
+
                 _compilationCallback = value;
             }
         }
@@ -81,6 +71,7 @@ public CSharpParseOptions ParseOptions
                 {
                     throw new ArgumentNullException(nameof(value));
                 }
+
                 _parseOptions = value;
             }
         }
@@ -97,9 +88,31 @@ public CSharpCompilationOptions CompilationOptions
                 {
                     throw new ArgumentNullException(nameof(value));
                 }
+
                 _compilationOptions = value;
             }
         }
 
+        /// <summary>
+        /// Gets the composite result of <see cref="FileProviders"/>.
+        /// </summary>
+        /// <returns>The <see cref="IFileProvider"/> instance if exactly one instance is registered, otherwise
+        /// a <see cref="CompositeFileProvider"/> that contains all registered instances.</returns>
+        public IFileProvider GetCompositeFileProvider()
+        {
+            if (_fileProvider == null)
+            {
+                if (FileProviders.Count == 1)
+                {
+                    _fileProvider = FileProviders[0];
+                }
+                else
+                {
+                    _fileProvider = new CompositeFileProvider(FileProviders);
+                }
+            }
+
+            return _fileProvider;
+        }
     }
 }

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

@@ -31,7 +31,7 @@ private static void ConfigureRazor(RazorViewEngineOptions razorOptions,
             IApplicationEnvironment applicationEnvironment,
             IHostingEnvironment hostingEnvironment)
         {
-            razorOptions.FileProvider = new PhysicalFileProvider(applicationEnvironment.ApplicationBasePath);
+            razorOptions.FileProviders.Add(new PhysicalFileProvider(applicationEnvironment.ApplicationBasePath));
 
             var parseOptions = new CSharpParseOptions(LanguageVersion.CSharp6);
             var compilationOptions = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary);

src/Microsoft.AspNet.Mvc.Razor/project.json

@@ -10,6 +10,7 @@
     "keyFile": "../../tools/Key.snk"
   },
   "dependencies": {
+    "Microsoft.AspNet.FileProviders.Composite": "1.0.0-*",
     "Microsoft.AspNet.Mvc.Razor.Host": "6.0.0-*",
     "Microsoft.AspNet.Mvc.ViewFeatures": "6.0.0-*",
     "Microsoft.AspNet.Razor.Runtime.Precompilation": "4.0.0-*",
@@ -26,8 +27,7 @@
       "type": "build"
     },
     "Microsoft.Dnx.Compilation.CSharp.Common": "1.0.0-*",
-    "Microsoft.Dnx.Compilation.CSharp.Abstractions": "1.0.0-*",
-    "Microsoft.Extensions.MemoryPool": "1.0.0-*"
+    "Microsoft.Dnx.Compilation.CSharp.Abstractions": "1.0.0-*"
   },
   "frameworks": {
     "net451": {

test/Microsoft.AspNet.Mvc.Razor.Test/Compilation/RazorCompilationServiceTest.cs

@@ -213,10 +213,8 @@ private static GeneratorResults GetGeneratorResult()
 
         private static IOptions<RazorViewEngineOptions> GetOptions(IFileProvider fileProvider = null)
         {
-            var razorViewEngineOptions = new RazorViewEngineOptions
-            {
-                FileProvider = fileProvider ?? new TestFileProvider()
-            };
+            var razorViewEngineOptions = new RazorViewEngineOptions();
+            razorViewEngineOptions.FileProviders.Add(fileProvider ?? new TestFileProvider());
             var options = new Mock<IOptions<RazorViewEngineOptions>>();
             options.SetupGet(o => o.Value)
                 .Returns(razorViewEngineOptions);

test/Microsoft.AspNet.Mvc.Razor.Test/Compilation/RoslynCompilationServiceTest.cs

@@ -224,17 +224,16 @@ public void GetCompilationFailedResult_ReturnsCompilationResult_WithGroupedMessa
             var generatedCodeFileName = "Generated Code";
             var fileProvider = new TestFileProvider();
             fileProvider.AddFile(viewPath, "view-content");
-            var options = new Mock<IOptions<RazorViewEngineOptions>>();
-            options.SetupGet(o => o.Value)
-                .Returns(new RazorViewEngineOptions
-                {
-                    FileProvider = fileProvider
-                });
+            var options = new RazorViewEngineOptions();
+            options.FileProviders.Add(fileProvider);
+            var optionsAccessor = new Mock<IOptions<RazorViewEngineOptions>>();
+            optionsAccessor.SetupGet(o => o.Value)
+                .Returns(options);
             var compilationService = new RoslynCompilationService(
                 PlatformServices.Default.Application,
                 CompilationServices.Default.LibraryExporter,
                 Mock.Of<IMvcRazorHost>(),
-                options.Object);
+                optionsAccessor.Object);
 
             var assemblyName = "random-assembly-name";
 
@@ -355,9 +354,9 @@ private static IOptions<RazorViewEngineOptions> GetOptions(IFileProvider filePro
         {
             var razorViewEngineOptions = new RazorViewEngineOptions
             {
-                FileProvider = fileProvider ?? new TestFileProvider(),
-                CompilationCallback = callback ?? (c => { })
+                CompilationCallback = callback ?? (c => { }),
             };
+            razorViewEngineOptions.FileProviders.Add(fileProvider ?? new TestFileProvider());
             var options = new Mock<IOptions<RazorViewEngineOptions>>();
             options
                 .SetupGet(o => o.Value)

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

@@ -1,7 +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.AspNet.FileProviders;
 using Microsoft.AspNet.Mvc.Internal;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
@@ -12,18 +12,27 @@ namespace Microsoft.AspNet.Mvc.Razor
     public class RazorViewEngineOptionsTest
     {
         [Fact]
-        public void FileProviderThrows_IfNullIsAssigned()
+        public void AddRazorOptions_ConfiguresOptionsAsExpected()
         {
             // Arrange
-            var options = new RazorViewEngineOptions();
+            var services = new ServiceCollection().AddOptions();
+            var fileProvider = new TestFileProvider();
 
-            // Act and Assert
-            var ex = Assert.Throws<ArgumentNullException>(() => options.FileProvider = null);
-            Assert.Equal("value", ex.ParamName);
+            // Act
+            var builder = new MvcBuilder(services);
+            builder.AddRazorOptions(options =>
+            {
+                options.FileProviders.Add(fileProvider);
+            });
+            var serviceProvider = services.BuildServiceProvider();
+
+            // Assert
+            var accessor = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
+            Assert.Same(fileProvider, accessor.Value.FileProviders[0]);
         }
 
         [Fact]
-        public void AddRazorOptions_ConfiguresOptionsProperly()
+        public void GetCompositeFileProvider_ReturnsInstanceIfExactlyOneFileProviderIsSpecified()
         {
             // Arrange
             var services = new ServiceCollection().AddOptions();
@@ -33,13 +42,54 @@ public void AddRazorOptions_ConfiguresOptionsProperly()
             var builder = new MvcBuilder(services);
             builder.AddRazorOptions(options =>
             {
-                options.FileProvider = fileProvider;
+                options.FileProviders.Add(fileProvider);
+            });
+            var serviceProvider = services.BuildServiceProvider();
+
+            // Assert
+            var accessor = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
+            Assert.Same(fileProvider, accessor.Value.GetCompositeFileProvider());
+        }
+
+        [Fact]
+        public void GetCompositeFileProvider_ReturnsCompositeFileProviderIfNoInstancesAreRegistered()
+        {
+            // Arrange
+            var services = new ServiceCollection().AddOptions();
+
+            // Act
+            var builder = new MvcBuilder(services);
+            builder.AddRazorOptions(options =>
+            {
+                options.FileProviders.Clear();
+            });
+            var serviceProvider = services.BuildServiceProvider();
+
+            // Assert
+            var accessor = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
+            var result = accessor.Value.GetCompositeFileProvider();
+            Assert.IsType<CompositeFileProvider>(result);
+        }
+
+        [Fact]
+        public void GetCompositeFileProvider_ReturnsCompositeFileProviderIfMoreThanOneInstanceIsRegistered()
+        {
+            // Arrange
+            var services = new ServiceCollection().AddOptions();
+
+            // Act
+            var builder = new MvcBuilder(services);
+            builder.AddRazorOptions(options =>
+            {
+                options.FileProviders.Add(new TestFileProvider());
+                options.FileProviders.Add(new TestFileProvider());
             });
             var serviceProvider = services.BuildServiceProvider();
 
             // Assert
             var accessor = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
-            Assert.Same(fileProvider, accessor.Value.FileProvider);
+            var result = accessor.Value.GetCompositeFileProvider();
+            Assert.IsType<CompositeFileProvider>(result);
         }
     }
 }