CompiledPageRouteModelProvider should de-dup descriptors

Fixes #7543

src/Microsoft.AspNetCore.Mvc.RazorPages/Internal/CompiledPageRouteModelProvider.cs

@@ -58,22 +58,55 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
             }
         }
 
-        /// <summary>
-        /// Gets the sequence of <see cref="CompiledViewDescriptor"/> from <paramref name="applicationManager"/>.
-        /// </summary>
-        /// <param name="applicationManager">The <see cref="ApplicationPartManager"/>s</param>
-        /// <returns>The sequence of <see cref="CompiledViewDescriptor"/>.</returns>
-        protected virtual IEnumerable<CompiledViewDescriptor> GetViewDescriptors(ApplicationPartManager applicationManager)
+        private IEnumerable<CompiledViewDescriptor> GetViewDescriptors(ApplicationPartManager applicationManager)
         {
             if (applicationManager == null)
             {
                 throw new ArgumentNullException(nameof(applicationManager));
             }
 
+            var viewsFeature = GetViewFeature(applicationManager);
+
+            var visited = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+            foreach (var viewDescriptor in viewsFeature.ViewDescriptors)
+            {
+                if (!visited.Add(viewDescriptor.RelativePath))
+                {
+                    // Already seen an descriptor with a higher "order"
+                    continue;
+                }
+
+                if (!viewDescriptor.IsPrecompiled)
+                {
+                    continue;
+                }
+
+                if (IsRazorPage(viewDescriptor))
+                {
+                    yield return viewDescriptor;
+                }
+            }
+
+            bool IsRazorPage(CompiledViewDescriptor viewDescriptor)
+            {
+                if (viewDescriptor.Item != null)
+                {
+                    return viewDescriptor.Item.Kind == RazorPageDocumentClassifierPass.RazorPageDocumentKind;
+                }
+                else if (viewDescriptor.ViewAttribute != null)
+                {
+                    return viewDescriptor.ViewAttribute is RazorPageAttribute;
+                }
+
+                return false;
+            }
+        }
+
+        protected virtual ViewsFeature GetViewFeature(ApplicationPartManager applicationManager)
+        {
             var viewsFeature = new ViewsFeature();
             applicationManager.PopulateFeature(viewsFeature);
-
-            return viewsFeature.ViewDescriptors.Where(d => d.IsPrecompiled && d.ViewAttribute is RazorPageAttribute);
+            return viewsFeature;
         }
 
         private void CreateModels(PageRouteModelProviderContext context)

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

@@ -484,5 +484,25 @@ Hello from /Pages/Shared/";
             // Assert
             Assert.Contains("Name is required", response);
         }
+
+        [Fact]
+        public async Task PagesFromClassLibraries_CanBeServed()
+        {
+            // Act
+            var response = await Client.GetStringAsync("/ClassLibraryPages/Served");
+
+            // Assert
+            Assert.Contains("This page is served from RazorPagesClassLibrary", response);
+        }
+
+        [Fact]
+        public async Task PagesFromClassLibraries_CanBeOverriden()
+        {
+            // Act
+            var response = await Client.GetStringAsync("/ClassLibraryPages/Overriden");
+
+            // Assert
+            Assert.Contains("This page is overriden by RazorPagesWebSite", response);
+        }
     }
 }

test/Microsoft.AspNetCore.Mvc.RazorPages.Test/Internal/CompiledPageRouteModelProviderTest.cs

@@ -518,6 +518,53 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
                 });
         }
 
+        [Fact]
+        public void OnProvidersExecuting_UsesTheFirstDescriptorForEachPath()
+        {
+            // ViewsFeature may contain duplicate entries for the same Page - for instance when an app overloads a library's views.
+            // It picks the first entry for each path. In the ordinary case, this should ensure that the app's Razor Pages are prefered
+            // to a Razor Page added by a library.
+
+            // Arrange
+            var descriptors = new[]
+            {
+                // Page coming from the app
+                CreateVersion_2_1_Descriptor("/Pages/About.cshtml", metadata: new object[]
+                {
+                    new RazorSourceChecksumAttribute("SHA1", GetChecksum("some content"), "/Pages/About.cshtml"),
+                }),
+                CreateVersion_2_1_Descriptor("/Pages/Home.cshtml", metadata: new object[]
+                {
+                    new RazorSourceChecksumAttribute("SHA1", GetChecksum("some content"), "/Pages/Index.cshtml"),
+                }),
+                // Page coming from the app
+                CreateVersion_2_1_Descriptor("/Pages/About.cshtml", metadata: new object[]
+                {
+                    new RazorSourceChecksumAttribute("SHA1", GetChecksum("some content"), "/Pages/About.cshtml"),
+                }),
+            };
+
+            var provider = CreateProvider(descriptors: descriptors);
+            var context = new PageRouteModelProviderContext();
+
+            // Act
+            provider.OnProvidersExecuting(context);
+
+            // Assert
+            Assert.Collection(
+                context.RouteModels,
+                result =>
+                {
+                    Assert.Equal("/Pages/About.cshtml", result.RelativePath);
+                    Assert.Equal("/About", result.ViewEnginePath);
+                },
+                result =>
+                {
+                    Assert.Equal("/Pages/Home.cshtml", result.RelativePath);
+                    Assert.Equal("/Home", result.ViewEnginePath);
+                });
+        }
+
         [Fact]
         public void GetRouteTemplate_ReturnsPathFromRazorPageAttribute()
         {
@@ -602,6 +649,7 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
         {
             return new CompiledViewDescriptor
             {
+                IsPrecompiled = true,
                 RelativePath = path,
                 ViewAttribute = new RazorPageAttribute(path, typeof(object), routeTemplate),
             };
@@ -613,6 +661,7 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
         {
             return new CompiledViewDescriptor
             {
+                IsPrecompiled = true,
                 RelativePath = path,
                 Item = new TestRazorCompiledItem(typeof(object), "mvc.1.0.razor-page", path, metadata ?? Array.Empty<object>()),
             };
@@ -631,7 +680,16 @@ namespace Microsoft.AspNetCore.Mvc.RazorPages.Internal
 
             public List<CompiledViewDescriptor> Descriptors { get; } = new List<CompiledViewDescriptor>();
 
-            protected override IEnumerable<CompiledViewDescriptor> GetViewDescriptors(ApplicationPartManager applicationManager) => Descriptors;
+            protected override ViewsFeature GetViewFeature(ApplicationPartManager applicationManager)
+            {
+                var feature = new ViewsFeature();
+                foreach (var descriptor in Descriptors)
+                {
+                    feature.ViewDescriptors.Add(descriptor);
+                }
+
+                return feature;
+            }
         }
     }
 }

test/WebSites/RazorPagesClassLibrary/Pages/ClassLibraryPages/Overriden.cshtml

@@ -0,0 +1,2 @@
+@page
+@{ throw new Exception("This page should be overriden by the application."); }

test/WebSites/RazorPagesClassLibrary/Pages/ClassLibraryPages/Served.cshtml

@@ -0,0 +1,2 @@
+@page
+This page is served from RazorPagesClassLibrary

test/WebSites/RazorPagesClassLibrary/RazorPagesClassLibrary.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk.Razor">
+
+  <PropertyGroup>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\src\Microsoft.AspNetCore.Mvc\Microsoft.AspNetCore.Mvc.csproj" />
+  </ItemGroup>
+
+</Project>

test/WebSites/RazorPagesWebSite/Pages/ClassLibraryPages/Overriden.cshtml

@@ -0,0 +1,2 @@
+@page
+This page is overriden by RazorPagesWebSite

test/WebSites/RazorPagesWebSite/RazorPagesWebSite.csproj

@@ -6,6 +6,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\..\src\Microsoft.AspNetCore.Mvc\Microsoft.AspNetCore.Mvc.csproj" />
+    <ProjectReference Include="..\RazorPagesClassLibrary\RazorPagesClassLibrary.csproj" />
 
     <PackageReference Include="Microsoft.AspNetCore.Authentication.Cookies" Version="$(MicrosoftAspNetCoreAuthenticationCookiesPackageVersion)" />
     <PackageReference Include="Microsoft.AspNetCore.Server.IISIntegration" Version="$(MicrosoftAspNetCoreServerIISIntegrationPackageVersion)" />