[Fixes #4550] Add an Option to set the Razor view location formats

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

@@ -462,6 +462,22 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             return string.Format(CultureInfo.CurrentCulture, GetString("Compilation_DependencyContextIsNotSpecified"), p0, p1, p2);
         }
 
+        /// <summary>
+        /// '{0}' cannot be empty. These locations are required to locate a view for rendering.
+        /// </summary>
+        internal static string ViewLocationFormatsIsRequired
+        {
+            get { return GetString("ViewLocationFormatsIsRequired"); }
+        }
+
+        /// <summary>
+        /// '{0}' cannot be empty. These locations are required to locate a view for rendering.
+        /// </summary>
+        internal static string FormatViewLocationFormatsIsRequired(object p0)
+        {
+            return string.Format(CultureInfo.CurrentCulture, GetString("ViewLocationFormatsIsRequired"), p0);
+        }
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);

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

@@ -8,7 +8,6 @@ using System.Globalization;
 using System.Linq;
 using System.Text.Encodings.Web;
 using Microsoft.AspNetCore.Mvc.Razor.Internal;
-using Microsoft.AspNetCore.Mvc.Routing;
 using Microsoft.AspNetCore.Mvc.ViewEngines;
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
@@ -21,12 +20,15 @@ namespace Microsoft.AspNetCore.Mvc.Razor
     /// Default implementation of <see cref="IRazorViewEngine"/>.
     /// </summary>
     /// <remarks>
-    /// For <c>ViewResults</c> returned from controllers, views should be located in <see cref="ViewLocationFormats"/>
+    /// For <c>ViewResults</c> returned from controllers, views should be located in
-    /// by default. For the controllers in an area, views should exist in <see cref="AreaViewLocationFormats"/>.
+    /// <see cref="RazorViewEngineOptions.ViewLocationFormats"/>
+    /// by default. For the controllers in an area, views should exist in
+    /// <see cref="RazorViewEngineOptions.AreaViewLocationFormats"/>.
     /// </remarks>
     public class RazorViewEngine : IRazorViewEngine
     {
-        private const string ViewExtension = ".cshtml";
+        public static readonly string ViewExtension = ".cshtml";
+
         private const string ControllerKey = "controller";
         private const string AreaKey = "area";
         private static readonly ViewLocationCacheItem[] EmptyViewStartLocationCacheItems =
@@ -34,10 +36,10 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         private static readonly TimeSpan _cacheExpirationDuration = TimeSpan.FromMinutes(20);
 
         private readonly IRazorPageFactoryProvider _pageFactory;
-        private readonly IList<IViewLocationExpander> _viewLocationExpanders;
         private readonly IRazorPageActivator _pageActivator;
         private readonly HtmlEncoder _htmlEncoder;
         private readonly ILogger _logger;
+        private readonly RazorViewEngineOptions _options;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="RazorViewEngine" />.
@@ -49,9 +51,24 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             IOptions<RazorViewEngineOptions> optionsAccessor,
             ILoggerFactory loggerFactory)
         {
+            _options = optionsAccessor.Value;
+
+            if (_options.ViewLocationFormats.Count == 0)
+            {
+                throw new ArgumentException(
+                    Resources.FormatViewLocationFormatsIsRequired(nameof(RazorViewEngineOptions.ViewLocationFormats)),
+                    nameof(optionsAccessor));
+            }
+
+            if (_options.AreaViewLocationFormats.Count == 0)
+            {
+                throw new ArgumentException(
+                    Resources.FormatViewLocationFormatsIsRequired(nameof(RazorViewEngineOptions.AreaViewLocationFormats)),
+                    nameof(optionsAccessor));
+            }
+
             _pageFactory = pageFactory;
             _pageActivator = pageActivator;
-            _viewLocationExpanders = optionsAccessor.Value.ViewLocationExpanders;
             _htmlEncoder = htmlEncoder;
             _logger = loggerFactory.CreateLogger<RazorViewEngine>();
             ViewLookupCache = new MemoryCache(new MemoryCacheOptions
@@ -60,47 +77,6 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             });
         }
 
-        /// <summary>
-        /// Gets the locations where this instance of <see cref="RazorViewEngine"/> will search for views.
-        /// </summary>
-        /// <remarks>
-        /// The locations of the views returned from controllers that do not belong to an area.
-        /// Locations are composite format strings (see http://msdn.microsoft.com/en-us/library/txafckwd.aspx),
-        /// which contains following indexes:
-        /// {0} - Action Name
-        /// {1} - Controller Name
-        /// The values for these locations are case-sensitive on case-sensitive file systems.
-        /// For example, the view for the <c>Test</c> action of <c>HomeController</c> should be located at
-        /// <c>/Views/Home/Test.cshtml</c>. Locations such as <c>/views/home/test.cshtml</c> would not be discovered
-        /// </remarks>
-        public virtual IEnumerable<string> ViewLocationFormats { get; } = new[]
-        {
-            "/Views/{1}/{0}" + ViewExtension,
-            "/Views/Shared/{0}" + ViewExtension,
-        };
-
-        /// <summary>
-        /// Gets the locations where this instance of <see cref="RazorViewEngine"/> will search for views within an
-        /// area.
-        /// </summary>
-        /// <remarks>
-        /// The locations of the views returned from controllers that belong to an area.
-        /// Locations are composite format strings (see http://msdn.microsoft.com/en-us/library/txafckwd.aspx),
-        /// which contains following indexes:
-        /// {0} - Action Name
-        /// {1} - Controller Name
-        /// {2} - Area name
-        /// The values for these locations are case-sensitive on case-sensitive file systems.
-        /// For example, the view for the <c>Test</c> action of <c>HomeController</c> should be located at
-        /// <c>/Views/Home/Test.cshtml</c>. Locations such as <c>/views/home/test.cshtml</c> would not be discovered
-        /// </remarks>
-        public virtual IEnumerable<string> AreaViewLocationFormats { get; } = new[]
-        {
-            "/Areas/{2}/Views/{1}/{0}" + ViewExtension,
-            "/Areas/{2}/Views/Shared/{0}" + ViewExtension,
-            "/Views/Shared/{0}" + ViewExtension,
-        };
-
         /// <summary>
         /// A cache for results of view lookups.
         /// </summary>
@@ -311,15 +287,15 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 isMainPage);
             Dictionary<string, string> expanderValues = null;
 
-            if (_viewLocationExpanders.Count > 0)
+            if (_options.ViewLocationExpanders.Count > 0)
             {
                 expanderValues = new Dictionary<string, string>(StringComparer.Ordinal);
                 expanderContext.Values = expanderValues;
 
                 // Perf: Avoid allocations
-                for (var i = 0; i < _viewLocationExpanders.Count; i++)
+                for (var i = 0; i < _options.ViewLocationExpanders.Count; i++)
                 {
-                    _viewLocationExpanders[i].PopulateValues(expanderContext);
+                    _options.ViewLocationExpanders[i].PopulateValues(expanderContext);
                 }
             }
 
@@ -385,13 +361,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor
             ViewLocationCacheKey cacheKey)
         {
             // Only use the area view location formats if we have an area token.
-            var viewLocations = !string.IsNullOrEmpty(expanderContext.AreaName) ?
+            IEnumerable<string> viewLocations = !string.IsNullOrEmpty(expanderContext.AreaName) ?
-                AreaViewLocationFormats :
+                _options.AreaViewLocationFormats :
-                ViewLocationFormats;
+                _options.ViewLocationFormats;
 
-            for (var i = 0; i < _viewLocationExpanders.Count; i++)
+            for (var i = 0; i < _options.ViewLocationExpanders.Count; i++)
             {
-                viewLocations = _viewLocationExpanders[i].ExpandViewLocations(expanderContext, viewLocations);
+                viewLocations = _options.ViewLocationExpanders[i].ExpandViewLocations(expanderContext, viewLocations);
             }
 
             ViewLocationCacheResult cacheResult = null;

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

@@ -20,7 +20,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         private Action<RoslynCompilationContext> _compilationCallback = c => { };
 
         /// <summary>
-        /// Get a <see cref="IList{IViewLocationExpander}"/> used by the <see cref="RazorViewEngine"/>.
+        /// Gets a <see cref="IList{IViewLocationExpander}"/> used by the <see cref="RazorViewEngine"/>.
         /// </summary>
         public IList<IViewLocationExpander> ViewLocationExpanders { get; }
             = new List<IViewLocationExpander>();
@@ -35,6 +35,61 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         /// </remarks>
         public IList<IFileProvider> FileProviders { get; } = new List<IFileProvider>();
 
+        /// <summary>
+        /// Gets the locations where <see cref="RazorViewEngine"/> will search for views.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// The locations of the views returned from controllers that do not belong to an area.
+        /// Locations are composite format strings (see http://msdn.microsoft.com/en-us/library/txafckwd.aspx),
+        /// which may contain the following format items:
+        /// </para>
+        /// <list type="bullet">
+        /// <item>
+        /// <description>{0} - Action Name</description>
+        /// </item>
+        /// <item>
+        /// <description>{1} - Controller Name</description>
+        /// </item>
+        /// </list>
+        /// <para>
+        /// The values for these locations are case-sensitive on case-sensitive file systems.
+        /// For example, the view for the <c>Test</c> action of <c>HomeController</c> should be located at
+        /// <c>/Views/Home/Test.cshtml</c>. Locations such as <c>/views/home/test.cshtml</c> would not be discovered.
+        /// </para>
+        /// </remarks>
+        public IList<string> ViewLocationFormats { get; } = new List<string>();
+
+        /// <summary>
+        /// Gets the locations where <see cref="RazorViewEngine"/> will search for views within an
+        /// area.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// The locations of the views returned from controllers that belong to an area.
+        /// Locations are composite format strings (see http://msdn.microsoft.com/en-us/library/txafckwd.aspx),
+        /// which may contain the following format items:
+        /// </para>
+        /// <list type="bullet">
+        /// <item>
+        /// <description>{0} - Action Name</description>
+        /// </item>
+        /// <item>
+        /// <description>{1} - Controller Name</description>
+        /// </item>
+        /// <item>
+        /// <description>{2} - Area Name</description>
+        /// </item>
+        /// </list>
+        /// <para>
+        /// The values for these locations are case-sensitive on case-sensitive file systems.
+        /// For example, the view for the <c>Test</c> action of <c>HomeController</c> under <c>Admin</c> area should
+        /// be located at <c>/Areas/Admin/Views/Home/Test.cshtml</c>.
+        /// Locations such as <c>/areas/admin/views/home/test.cshtml</c> would not be discovered.
+        /// </para>
+        /// </remarks>
+        public IList<string> AreaViewLocationFormats { get; } = new List<string>();
+
         /// <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.

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

@@ -50,6 +50,13 @@ namespace Microsoft.AspNetCore.Mvc
             var parseOptions = razorOptions.ParseOptions;
             razorOptions.ParseOptions = parseOptions.WithPreprocessorSymbols(
                 parseOptions.PreprocessorSymbolNames.Concat(new[] { configurationSymbol }));
+
+            razorOptions.ViewLocationFormats.Add("/Views/{1}/{0}" + RazorViewEngine.ViewExtension);
+            razorOptions.ViewLocationFormats.Add("/Views/Shared/{0}" + RazorViewEngine.ViewExtension);
+
+            razorOptions.AreaViewLocationFormats.Add("/Areas/{2}/Views/{1}/{0}" + RazorViewEngine.ViewExtension);
+            razorOptions.AreaViewLocationFormats.Add("/Areas/{2}/Views/Shared/{0}" + RazorViewEngine.ViewExtension);
+            razorOptions.AreaViewLocationFormats.Add("/Views/Shared/{0}" + RazorViewEngine.ViewExtension);
         }
     }
 }

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

@@ -203,4 +203,7 @@
   <data name="Compilation_DependencyContextIsNotSpecified" xml:space="preserve">
     <value>The Razor page '{0}' failed to compile. Ensure that your application's {1} sets the '{2}' compilation property.</value>
   </data>
+  <data name="ViewLocationFormatsIsRequired" xml:space="preserve">
+    <value>'{0}' cannot be empty. These locations are required to locate a view for rendering.</value>
+  </data>
 </root>

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

@@ -1,6 +1,8 @@
 // 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.Linq;
 using Microsoft.AspNetCore.Mvc.ApplicationParts;
 using Microsoft.AspNetCore.Mvc.Internal;
 using Microsoft.Extensions.DependencyInjection;
@@ -11,6 +13,67 @@ namespace Microsoft.AspNetCore.Mvc.Razor
 {
     public class RazorViewEngineOptionsTest
     {
+        [Fact]
+        public void AreaViewLocationFormats_ContainsExpectedLocations()
+        {
+            // Arrange
+            var services = new ServiceCollection().AddOptions();
+            var areaViewLocations = new[]
+            {
+                "/Areas/{2}/MvcViews/{1}/{0}.cshtml",
+                "/Areas/{2}/MvcViews/Shared/{0}.cshtml",
+                "/MvcViews/Shared/{0}.cshtml"
+            };
+            var builder = new MvcBuilder(services, new ApplicationPartManager());
+            builder.AddRazorOptions(options =>
+            {
+                options.AreaViewLocationFormats.Clear();
+
+                foreach (var location in areaViewLocations)
+                {
+                    options.AreaViewLocationFormats.Add(location);
+                }
+            });
+            var serviceProvider = services.BuildServiceProvider();
+            var accessor = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
+
+            // Act
+            var formats = accessor.Value.AreaViewLocationFormats;
+
+            // Assert
+            Assert.Equal(areaViewLocations, formats, StringComparer.Ordinal);
+        }
+
+        [Fact]
+        public void ViewLocationFormats_ContainsExpectedLocations()
+        {
+            // Arrange
+            var services = new ServiceCollection().AddOptions();
+            var viewLocations = new[]
+            {
+                "/MvcViews/{1}/{0}.cshtml",
+                "/MvcViews/Shared/{0}.cshtml"
+            };
+            var builder = new MvcBuilder(services, new ApplicationPartManager());
+            builder.AddRazorOptions(options =>
+            {
+                options.ViewLocationFormats.Clear();
+
+                foreach (var location in viewLocations)
+                {
+                    options.ViewLocationFormats.Add(location);
+                }
+            });
+            var serviceProvider = services.BuildServiceProvider();
+            var accessor = serviceProvider.GetRequiredService<IOptions<RazorViewEngineOptions>>();
+
+            // Act
+            var formats = accessor.Value.ViewLocationFormats;
+
+            // Assert
+            Assert.Equal(viewLocations, formats, StringComparer.Ordinal);
+        }
+
         [Fact]
         public void AddRazorOptions_ConfiguresOptionsAsExpected()
         {

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

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Threading;
+using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc.Abstractions;
 using Microsoft.AspNetCore.Mvc.Routing;
@@ -364,10 +365,9 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
                 .Verifiable();
             var viewEngine = new TestableRazorViewEngine(
                 pageFactory.Object,
-                GetOptionsAccessor());
+                GetOptionsAccessor(
-            viewEngine.SetLocationFormats(
+                    viewLocationFormats: new[] { "fake-path1/{1}/{0}.rzr" },
-                new[] { "fake-path1/{1}/{0}.rzr" },
+                    areaViewLocationFormats: new[] { "fake-area-path/{2}/{1}/{0}.rzr" }));
-                new[] { "fake-area-path/{2}/{1}/{0}.rzr" });
             var context = GetActionContext(_controllerTestContext);
 
             // Act
@@ -393,10 +393,9 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
                 .Verifiable();
             var viewEngine = new TestableRazorViewEngine(
                 pageFactory.Object,
-                GetOptionsAccessor());
+                GetOptionsAccessor(
-            viewEngine.SetLocationFormats(
+                    viewLocationFormats: new[] { "fake-path1/{1}/{0}.rzr" },
-                new[] { "fake-path1/{1}/{0}.rzr" },
+                    areaViewLocationFormats: new[] { "fake-area-path/{2}/{1}/{0}.rzr" }));
-                new[] { "fake-area-path/{2}/{1}/{0}.rzr" });
             var context = GetActionContext(_areaTestContext);
 
             // Act
@@ -1462,38 +1461,6 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
             Assert.Equal(expectedPagePath, result);
         }
 
-        [Fact]
-        public void AreaViewLocationFormats_ContainsExpectedLocations()
-        {
-            // Arrange
-            var viewEngine = CreateViewEngine();
-            var areaViewLocations = new string[]
-            {
-                "/Areas/{2}/Views/{1}/{0}.cshtml",
-                "/Areas/{2}/Views/Shared/{0}.cshtml",
-                "/Views/Shared/{0}.cshtml"
-            };
-
-            // Act & Assert
-            Assert.Equal(areaViewLocations, viewEngine.AreaViewLocationFormats);
-        }
-
-        [Fact]
-        public void ViewLocationFormats_ContainsExpectedLocations()
-        {
-            // Arrange
-            var viewEngine = CreateViewEngine();
-
-            var viewLocations = new string[]
-            {
-                "/Views/{1}/{0}.cshtml",
-                "/Views/Shared/{0}.cshtml"
-            };
-
-            // Act & Assert
-            Assert.Equal(viewLocations, viewEngine.ViewLocationFormats);
-        }
-
         [Fact]
         public void GetNormalizedRouteValue_ReturnsValueFromRouteValues_IfKeyHandlingIsRequired()
         {
@@ -1713,15 +1680,19 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
             IEnumerable<IViewLocationExpander> expanders = null)
         {
             pageFactory = pageFactory ?? Mock.Of<IRazorPageFactoryProvider>();
-            return new TestableRazorViewEngine(
+            return new TestableRazorViewEngine(pageFactory, GetOptionsAccessor(expanders));
-                pageFactory,
-                GetOptionsAccessor(expanders));
         }
 
         private static IOptions<RazorViewEngineOptions> GetOptionsAccessor(
-            IEnumerable<IViewLocationExpander> expanders = null)
+            IEnumerable<IViewLocationExpander> expanders = null,
+            IEnumerable<string> viewLocationFormats = null,
+            IEnumerable<string> areaViewLocationFormats = null)
         {
+            var optionsSetup = new RazorViewEngineOptionsSetup(Mock.Of<IHostingEnvironment>());
+
             var options = new RazorViewEngineOptions();
+            optionsSetup.Configure(options);
+
             if (expanders != null)
             {
                 foreach (var expander in expanders)
@@ -1730,6 +1701,26 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
                 }
             }
 
+            if (viewLocationFormats != null)
+            {
+                options.ViewLocationFormats.Clear();
+
+                foreach (var location in viewLocationFormats)
+                {
+                    options.ViewLocationFormats.Add(location);
+                }
+            }
+
+            if (areaViewLocationFormats != null)
+            {
+                options.AreaViewLocationFormats.Clear();
+
+                foreach (var location in areaViewLocationFormats)
+                {
+                    options.AreaViewLocationFormats.Add(location);
+                }
+            }
+
             var optionsAccessor = new Mock<IOptions<RazorViewEngineOptions>>();
             optionsAccessor
                 .SetupGet(v => v.Value)
@@ -1784,9 +1775,6 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
 
         private class TestableRazorViewEngine : RazorViewEngine
         {
-            private IEnumerable<string> _viewLocationFormats;
-            private IEnumerable<string> _areaViewLocationFormats;
-
             public TestableRazorViewEngine(
                 IRazorPageFactoryProvider pageFactory,
                 IOptions<RazorViewEngineOptions> optionsAccessor)
@@ -1794,20 +1782,6 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
             {
             }
 
-            public void SetLocationFormats(
-                IEnumerable<string> viewLocationFormats,
-                IEnumerable<string> areaViewLocationFormats)
-            {
-                _viewLocationFormats = viewLocationFormats;
-                _areaViewLocationFormats = areaViewLocationFormats;
-            }
-
-            public override IEnumerable<string> ViewLocationFormats =>
-                _viewLocationFormats != null ? _viewLocationFormats : base.ViewLocationFormats;
-
-            public override IEnumerable<string> AreaViewLocationFormats =>
-                _areaViewLocationFormats != null ? _areaViewLocationFormats : base.AreaViewLocationFormats;
-
             public IMemoryCache ViewLookupCachePublic => ViewLookupCache;
         }
     }

test/Microsoft.AspNetCore.Mvc.Test/RazorViewEngineOptionsSetupTest.cs

@@ -1,12 +1,10 @@
 // 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.IO;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Razor;
 using Microsoft.CodeAnalysis;
 using Microsoft.Extensions.FileProviders;
-using Microsoft.Extensions.PlatformAbstractions;
 using Moq;
 using Xunit;