Ensure ApplicationPart attributes are added during incremental builds (dotnet/razor#686)

Fixes https://github.com/aspnet/AspNetCore/issues/11315\n\nCommit migrated from dotnet/razor@1a7a74b

Author: pranavkm

src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.MvcApplicationPartsDiscovery.targets

@@ -67,7 +67,16 @@ Copyright (c) .NET Foundation. All rights reserved.
       OutputFile="$(_MvcApplicationPartAttributeGeneratedFile)"
       Condition="'@(_ApplicationPartAssemblyNames->Count())' != '0'" />
 
-    <ItemGroup Condition="'@(_ApplicationPartAssemblyNames->Count())' != '0'">
+    <!--
+      If the generated attribute file exists, but no assembly names were discovered,
+      it suggests that the assembly references were changed to no longer point to MVC.
+      In this case, delete the file so that future incremental builds can no longer pick it up.
+    -->
+    <Delete
+      File="$(_MvcApplicationPartAttributeGeneratedFile)"
+      Condition="'@(_ApplicationPartAssemblyNames->Count())' == '0' AND Exists('$(_MvcApplicationPartAttributeGeneratedFile)')" />
+
+    <ItemGroup Condition="Exists('$(_MvcApplicationPartAttributeGeneratedFile)')">
       <Compile Remove="$(_MvcApplicationPartAttributeGeneratedFile)" Condition="'$(Language)'!='F#'" />
       <Compile Include="$(_MvcApplicationPartAttributeGeneratedFile)"  Condition="'$(Language)'!='F#'" />
 

src/Razor/Microsoft.NET.Sdk.Razor/test/IntegrationTests/ApplicationPartDiscoveryIntegrationTest.cs

@@ -34,6 +34,7 @@ private async Task Build_ProjectWithDependencyThatReferencesMvc_AddsAttribute(MS
 
             Assert.FileExists(result, IntermediateOutputPath, "AppWithP2PReference.MvcApplicationPartsAssemblyInfo.cs");
             Assert.FileContains(result, Path.Combine(IntermediateOutputPath, "AppWithP2PReference.MvcApplicationPartsAssemblyInfo.cs"), "[assembly: Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute(\"ClassLibrary\")]");
+            Assert.AssemblyHasAttribute(result, Path.Combine(OutputPath, "AppWithP2PReference.dll"), "Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute");
         }
 
         [Fact]
@@ -69,6 +70,33 @@ public async Task BuildIncrementalism_WhenApplicationPartAttributeIsGenerated()
 
             Assert.FileExists(result, generatedAttributeFile);
             Assert.Equal(thumbPrint, GetThumbPrint(generatedAttributeFile));
+            Assert.AssemblyHasAttribute(result, Path.Combine(OutputPath, "AppWithP2PReference.dll"), "Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute");
+        }
+
+        // Regression test for https://github.com/aspnet/AspNetCore/issues/11315
+        [Fact]
+        [InitializeTestProject("AppWithP2PReference", additionalProjects: "ClassLibrary")]
+        public async Task BuildIncrementalism_CausingRecompilation_WhenApplicationPartAttributeIsGenerated()
+        {
+            var result = await DotnetMSBuild("Build");
+
+            Assert.BuildPassed(result);
+
+            var generatedAttributeFile = Path.Combine(IntermediateOutputPath, "AppWithP2PReference.MvcApplicationPartsAssemblyInfo.cs");
+            Assert.FileExists(result, generatedAttributeFile);
+            Assert.FileContains(result, generatedAttributeFile, "[assembly: Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute(\"ClassLibrary\")]");
+
+            var thumbPrint = GetThumbPrint(generatedAttributeFile);
+
+            // Touch a file in the main app which should call recompilation, but not the Mvc discovery tasks to re-run.
+            File.AppendAllText(Path.Combine(Project.DirectoryPath, "Program.cs"), " ");
+            result = await DotnetMSBuild("Build");
+
+            Assert.BuildPassed(result);
+
+            Assert.FileExists(result, generatedAttributeFile);
+            Assert.Equal(thumbPrint, GetThumbPrint(generatedAttributeFile));
+            Assert.AssemblyHasAttribute(result, Path.Combine(OutputPath, "AppWithP2PReference.dll"), "Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute");
         }
 
         [Fact]
@@ -88,6 +116,7 @@ public async Task Build_ProjectWithDependencyThatReferencesMvc_AddsAttributeToNo
 
             Assert.FileExists(result, IntermediateOutputPath, "SimpleMvcFSharp.MvcApplicationPartsAssemblyInfo.fs");
             Assert.FileContains(result, Path.Combine(IntermediateOutputPath, "SimpleMvcFSharp.MvcApplicationPartsAssemblyInfo.fs"), "<assembly: Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute(\"ClassLibrary\")>");
+            Assert.AssemblyHasAttribute(result, Path.Combine(OutputPath, "SimpleMvcFSharp.dll"), "Microsoft.AspNetCore.Mvc.ApplicationParts.ApplicationPartAttribute");
         }
 
         [Fact]

src/Razor/Microsoft.NET.Sdk.Razor/test/IntegrationTests/Assert.cs

@@ -507,6 +507,36 @@ private static IEnumerable<string> GetDeclaredTypeNames(string assemblyPath)
             }
         }
 
+        public static void AssemblyHasAttribute(MSBuildResult result, string assemblyPath, string fullTypeName)
+        {
+            if (result == null)
+            {
+                throw new ArgumentNullException(nameof(result));
+            }
+
+            assemblyPath = Path.Combine(result.Project.DirectoryPath, Path.Combine(assemblyPath));
+
+            var typeNames = GetAssemblyAttributes(assemblyPath);
+            Assert.Contains(fullTypeName, typeNames);
+        }
+
+        private static IEnumerable<string> GetAssemblyAttributes(string assemblyPath)
+        {
+            using (var file = File.OpenRead(assemblyPath))
+            {
+                var peReader = new PEReader(file);
+                var metadataReader = peReader.GetMetadataReader();
+                return metadataReader.CustomAttributes.Where(t => !t.IsNil).Select(t =>
+                {
+                    var attribute = metadataReader.GetCustomAttribute(t);
+                    var constructor = metadataReader.GetMemberReference((MemberReferenceHandle)attribute.Constructor);
+                    var type = metadataReader.GetTypeReference((TypeReferenceHandle)constructor.Parent);
+
+                    return metadataReader.GetString(type.Namespace) + "." + metadataReader.GetString(type.Name);
+                }).ToArray();
+            }
+        }
+
         private abstract class MSBuildXunitException : Xunit.Sdk.XunitException
         {
             protected MSBuildXunitException(MSBuildResult result)