Allow "page" route parameter to be used in Mvc controllers

Fixes #6660

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

@@ -240,7 +240,13 @@ namespace Microsoft.AspNetCore.Mvc.Razor
         {
             var controllerName = GetNormalizedRouteValue(actionContext, ControllerKey);
             var areaName = GetNormalizedRouteValue(actionContext, AreaKey);
-            var razorPageName = GetNormalizedRouteValue(actionContext, PageKey);
+            string razorPageName = null;
+            if (actionContext.ActionDescriptor.RouteValues.ContainsKey(PageKey))
+            {
+                // Only calculate the Razor Page name if "page" is registered in RouteValues.
+                razorPageName = GetNormalizedRouteValue(actionContext, PageKey);
+            }
+
             var expanderContext = new ViewLocationExpanderContext(
                 actionContext,
                 pageName,
@@ -270,8 +276,7 @@ namespace Microsoft.AspNetCore.Mvc.Razor
                 expanderContext.IsMainPage,
                 expanderValues);
 
-            ViewLocationCacheResult cacheResult;
-            if (!ViewLookupCache.TryGetValue(cacheKey, out cacheResult))
+            if (!ViewLookupCache.TryGetValue(cacheKey, out ViewLocationCacheResult cacheResult))
             {
                 _logger.ViewLookupCacheMiss(cacheKey.ViewName, cacheKey.ControllerName);
                 cacheResult = OnCacheMiss(expanderContext, cacheKey);

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

@@ -10,13 +10,13 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
     {
         public IEnumerable<string> ExpandViewLocations(ViewLocationExpanderContext context, IEnumerable<string> viewLocations)
         {
-            if (string.IsNullOrEmpty(context.PageName))
+            if ((context.ActionContext.ActionDescriptor is PageActionDescriptor) && !string.IsNullOrEmpty(context.PageName))
             {
-                // Not a page - just act natural.
-                return viewLocations;
+                return ExpandPageHierarchy();
             }
 
-            return ExpandPageHierarchy();
+            // Not a page - just act natural.
+            return viewLocations;
 
             IEnumerable<string> ExpandPageHierarchy()
             {

test/Microsoft.AspNetCore.Mvc.FunctionalTests/BasicTests.cs

@@ -376,5 +376,31 @@ namespace Microsoft.AspNetCore.Mvc.FunctionalTests
             // Assert
             Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
         }
+
+        [Fact]
+        public async Task UsingPageRouteParameterInConventionalRouteWorks()
+        {
+            // Arrange
+            var expected = "ConventionalRoute - Hello from mypage";
+
+            // Act
+            var response = await Client.GetStringAsync("/PageRoute/ConventionalRoute/mypage");
+
+            // Assert
+            Assert.Equal(expected, response.Trim());
+        }
+
+        [Fact]
+        public async Task UsingPageRouteParameterInAttributeRouteWorks()
+        {
+            // Arrange
+            var expected = "AttributeRoute - Hello from test-page";
+
+            // Act
+            var response = await Client.GetStringAsync("/PageRoute/Attribute/test-page");
+
+            // Assert
+            Assert.Equal(expected, response.Trim());
+        }
     }
 }

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

@@ -1791,6 +1791,79 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
             Assert.Equal(expected, actual);
         }
 
+        [Fact]
+        public void ViewEngine_DoesNotSetPageValue_IfItIsNotSpecifiedInRouteValues()
+        {
+            // Arrange
+            var routeValues = new Dictionary<string, object>
+            {
+                { "controller", "MyController" },
+                { "action", "MyAction" }
+            };
+
+            var expected = new[] { "some-seed" };
+            var expander = new Mock<IViewLocationExpander>();
+            expander
+                .Setup(e => e.PopulateValues(It.IsAny<ViewLocationExpanderContext>()))
+                .Callback((ViewLocationExpanderContext c) =>
+                {
+                    Assert.Equal("MyController", c.ControllerName);
+                    Assert.Null(c.PageName);
+                })
+                .Verifiable();
+
+            expander
+                .Setup(e => e.ExpandViewLocations(
+                    It.IsAny<ViewLocationExpanderContext>(),
+                    It.IsAny<IEnumerable<string>>()))
+                .Returns(expected);
+
+            var viewEngine = CreateViewEngine(expanders: new[] { expander.Object });
+            var context = GetActionContext(routeValues);
+
+            // Act
+            viewEngine.FindView(context, viewName: "Test-view", isMainPage: true);
+
+            // Assert
+            expander.Verify();
+        }
+
+        [Fact]
+        public void ViewEngine_SetsPageValue_IfItIsSpecifiedInRouteValues()
+        {
+            // Arrange
+            var routeValues = new Dictionary<string, object>
+            {
+                { "page", "MyPage" },
+            };
+
+            var expected = new[] { "some-seed" };
+            var expander = new Mock<IViewLocationExpander>();
+            expander
+                .Setup(e => e.PopulateValues(It.IsAny<ViewLocationExpanderContext>()))
+                .Callback((ViewLocationExpanderContext c) =>
+                {
+                    Assert.Equal("MyPage", c.PageName);
+                })
+                .Verifiable();
+
+            expander
+                .Setup(e => e.ExpandViewLocations(
+                    It.IsAny<ViewLocationExpanderContext>(),
+                    It.IsAny<IEnumerable<string>>()))
+                .Returns(expected);
+
+            var viewEngine = CreateViewEngine(expanders: new[] { expander.Object });
+            var context = GetActionContext(routeValues);
+            context.ActionDescriptor.RouteValues["page"] = "MyPage";
+
+            // Act
+            viewEngine.FindView(context, viewName: "MyView", isMainPage: true);
+
+            // Assert
+            expander.Verify();
+        }
+
         // Return RazorViewEngine with a page factory provider that is always successful.
         private RazorViewEngine CreateSuccessfulViewEngine()
         {
@@ -1931,8 +2004,8 @@ namespace Microsoft.AspNetCore.Mvc.Razor.Test
                       optionsAccessor,
                       new FileProviderRazorProject(
                           Mock.Of<IRazorViewEngineFileProviderAccessor>(a => a.FileProvider == new TestFileProvider())))
-                      {
-                      }
+            {
+            }
 
             public TestableRazorViewEngine(
                 IRazorPageFactoryProvider pageFactory,

test/Microsoft.AspNetCore.Mvc.RazorPages.Test/Infrastructure/PageViewLocationExpanderTest.cs

@@ -1,13 +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;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
-using System.Text;
+using Microsoft.AspNetCore.Mvc.Controllers;
 using Microsoft.AspNetCore.Mvc.Razor;
-using Microsoft.AspNetCore.Razor.Language;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
@@ -48,6 +45,28 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
             Assert.Equal(locations, actual);
         }
 
+        [Fact]
+        public void ExpandLocations_NoOp_ForNonPageWithPageName()
+        {
+            // Verifies the fix for https://github.com/aspnet/Mvc/issues/6660. This ensures that when PageViewLocationExpander is called
+            // from a non-Razor Page with a route value for "
+            // Arrange
+            var context = CreateContext(pageName: "test");
+            context.ActionContext.ActionDescriptor = new ControllerActionDescriptor();
+            var locations = new string[]
+            {
+                "/ignore-me",
+            };
+
+            var expander = new PageViewLocationExpander();
+
+            // Act
+            var actual = expander.ExpandViewLocations(context, locations);
+
+            // Assert
+            Assert.Equal(locations, actual);
+        }
+
         [Fact]
         public void ExpandLocations_NoOp_WhenLocationDoesNotContainPageToken()
         {
@@ -125,8 +144,13 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
 
         private ViewLocationExpanderContext CreateContext(string viewName = "_LoginPartial.cshtml", string pageName = null)
         {
+            var actionContext = new ActionContext
+            {
+                ActionDescriptor = new PageActionDescriptor(),
+            };
+
             return new ViewLocationExpanderContext(
-                new ActionContext(),
+                actionContext,
                 viewName,
                 controllerName: null,
                 areaName: null,
@@ -134,6 +158,7 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Infrastructure
                 isMainPage: true)
             {
                 Values = new Dictionary<string, string>(),
+                
             };
         }
     }

test/WebSites/BasicWebSite/Controllers/PageRouteController.cs

@@ -0,0 +1,25 @@
+// 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 Microsoft.AspNetCore.Mvc;
+
+namespace BasicWebSite.Controllers
+{
+    // Verifies that we can use the "page" token in routing in a controller only (no Razor Pages) application
+    // without affecting view lookups.
+    public class PageRouteController : Controller
+    {
+        public IActionResult ConventionalRoute(string page)
+        {
+            ViewData["page"] = page;
+            return View();
+        }
+
+        [HttpGet("/PageRoute/Attribute/{page}")]
+        public IActionResult AttributeRoute(string page)
+        {
+            ViewData["page"] = page;
+            return View();
+        }
+    }
+}

test/WebSites/BasicWebSite/Startup.cs

@@ -44,6 +44,7 @@ namespace BasicWebSite
                 routes.MapRoute("ActionAsMethod", "{controller}/{action}",
                     defaults: new { controller = "Home", action = "Index" });
 
+                routes.MapRoute("PageRoute", "{controller}/{action}/{page}");
             });
         }
     }

test/WebSites/BasicWebSite/Views/PageRoute/AttributeRoute.cshtml

@@ -0,0 +1 @@
+AttributeRoute - Hello from @ViewBag.Page

test/WebSites/BasicWebSite/Views/PageRoute/ConventionalRoute.cshtml

@@ -0,0 +1 @@
+ConventionalRoute - Hello from @ViewBag.Page