Preserve files being published to the publish root and the wwwroot (#19938)

* Preserve files being published to the publish root and the wwwroot

Fixes https://github.com/dotnet/aspnetcore/issues/19926

src/Components/WebAssembly/Build/src/build/netstandard1.0/Microsoft.AspNetCore.Components.WebAssembly.Build.props

@@ -1,3 +1,7 @@
 <Project>
   <Import Project="$(MSBuildThisFileDirectory)..\..\targets\All.props" />
+
+  <PropertyGroup>
+    <ReferencesComponentsWebAssemblyBuild>true</ReferencesComponentsWebAssemblyBuild>
+  </PropertyGroup>
 </Project>

src/Components/WebAssembly/Build/src/targets/Blazor.MonoRuntime.targets

@@ -272,6 +272,15 @@
     <ReadLinesFromFile File="$(_BlazorApplicationAssembliesCacheFile)" Condition="'@(_BlazorResolvedAssembly->Count())' == '0'">
       <Output TaskParameter="Lines" ItemName="_BlazorResolvedAssembly"/>
     </ReadLinesFromFile>
+
+    <ItemGroup>
+      <!--
+        Workaround for https://github.com/dotnet/aspnetcore/issues/19926. Add _BlazorResolvedAssembly to FileWrites so that these files
+        do not get removed during an incremental build. Note that we add these files here as opposed to _ResolveBlazorRuntimeDependencies
+        since the task that calculates these items in _ResolveBlazorRuntimeDependencies does not execute in incremental builds.
+       -->
+      <FileWrites Include="$(_BlazorResolvedAssembly)"/>
+    </ItemGroup>
   </Target>
 
   <Target
@@ -291,9 +300,20 @@
       ApplicationDependencies="@(_BlazorManagedRuntimeAssembly)"
       WebAssemblyBCLAssemblies="@(_WebAssemblyBCLAssembly)">
 
-      <Output TaskParameter="Dependencies" ItemName="_BlazorResolvedAssembly" />
+      <Output TaskParameter="Dependencies" ItemName="_BlazorResolvedAssemblyUnlinked" />
     </ResolveBlazorRuntimeDependencies>
 
+    <!--
+    Workaround for https://github.com/dotnet/aspnetcore/issues/19926. Using the files from their initial locations
+    as-is causes RazorSDK to remove files from a hosted app's publish directory. This is because files being removed
+    are looked up by their path. We'll copy files to an intermediate location to avoid the removal code.
+    -->
+    <Copy
+      SourceFiles="@(_BlazorResolvedAssemblyUnlinked)"
+      DestinationFolder="$(_BlazorIntermediateOutputPath)unlinked">
+        <Output TaskParameter="CopiedFiles" ItemName="_BlazorResolvedAssembly" />
+    </Copy>
+
     <WriteLinesToFile File="$(_BlazorApplicationAssembliesCacheFile)" Lines="@(_BlazorResolvedAssembly)" Overwrite="true" />
 
     <ItemGroup>

src/Components/WebAssembly/Build/test/BuildIntegrationTests/PublishIntegrationTest.cs

@@ -178,18 +178,23 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
         }
 
         [Fact]
-        public async Task Publish_HostedApp_Works()
+        public async Task Publish_HostedApp_WithLinkOnBuildTrue_Works()
         {
             // Arrange
             using var project = ProjectDirectory.Create("blazorhosted", additionalProjects: new[] { "standalone", "razorclasslibrary", });
             project.TargetFramework = "netcoreapp3.1";
             var result = await MSBuildProcessManager.DotnetMSBuild(project, "Publish");
+            AddSiblingProjectFileContent(project, @"
+<PropertyGroup>
+    <BlazorWebAssemblyEnableLinking>true</BlazorWebAssemblyEnableLinking>
+</PropertyGroup>");
 
             Assert.BuildPassed(result);
 
             var publishDirectory = project.PublishOutputDirectory;
             // Make sure the main project exists
             Assert.FileExists(result, publishDirectory, "blazorhosted.dll");
+            Assert.FileExists(result, publishDirectory, "RazorClassLibrary.dll");
 
             var blazorPublishDirectory = Path.Combine(publishDirectory, "wwwroot");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "blazor.boot.json");
@@ -198,6 +203,10 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "wasm", DotNetJsFileName);
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "_bin", "standalone.dll");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "_bin", "Microsoft.Extensions.Logging.Abstractions.dll"); // Verify dependencies are part of the output.
+            // Verify project references appear as static web assets
+            Assert.FileExists(result, blazorPublishDirectory, "_framework", "_bin", "RazorClassLibrary.dll");
+            // Also verify project references to the server project appear in the publish output
+            Assert.FileExists(result, publishDirectory, "RazorClassLibrary.dll");
 
             // Verify static assets are in the publish directory
             Assert.FileExists(result, blazorPublishDirectory, "index.html");
@@ -224,7 +233,7 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
             using var project = ProjectDirectory.Create("blazorhosted", additionalProjects: new[] { "standalone", "razorclasslibrary", });
             project.TargetFramework = "netcoreapp3.1";
 
-            AddSiblingProjectFileContent(@"
+            AddSiblingProjectFileContent(project, @"
 <PropertyGroup>
     <BlazorWebAssemblyEnableLinking>false</BlazorWebAssemblyEnableLinking>
 </PropertyGroup>");
@@ -241,12 +250,18 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
             // Make sure the main project exists
             Assert.FileExists(result, publishDirectory, "blazorhosted.dll");
 
+            // Verification for https://github.com/dotnet/aspnetcore/issues/19926. Verify binaries for projects
+            // referenced by the Hosted project appear in the publish directory
+            Assert.FileExists(result, publishDirectory, "RazorClassLibrary.dll");
+            Assert.FileExists(result, publishDirectory, "standalone.dll");
+
             var blazorPublishDirectory = Path.Combine(publishDirectory, "wwwroot");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "blazor.boot.json");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "blazor.webassembly.js");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "wasm", "dotnet.wasm");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "wasm", DotNetJsFileName);
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "_bin", "standalone.dll");
+            Assert.FileExists(result, blazorPublishDirectory, "_framework", "_bin", "RazorClassLibrary.dll");
             Assert.FileExists(result, blazorPublishDirectory, "_framework", "_bin", "Microsoft.Extensions.Logging.Abstractions.dll"); // Verify dependencies are part of the output.
 
             // Verify static assets are in the publish directory
@@ -268,14 +283,7 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
                 serviceWorkerContent: "// This is the production service worker",
                 assetsManifestPath: "custom-service-worker-assets.js");
 
-            void AddSiblingProjectFileContent(string content)
-            {
-                var path = Path.Combine(project.SolutionPath, "standalone", "standalone.csproj");
-                var existing = File.ReadAllText(path);
-                var updated = existing.Replace("<!-- Test Placeholder -->", content);
-                File.WriteAllText(path, updated);
             }
-        }
 
         [Fact]
         public async Task Publish_HostedApp_WithNoBuild_Works()
@@ -319,6 +327,14 @@ namespace Microsoft.AspNetCore.Components.WebAssembly.Build
                 assetsManifestPath: "custom-service-worker-assets.js");
         }
 
+        private static void AddSiblingProjectFileContent(ProjectDirectory project, string content)
+        {
+            var path = Path.Combine(project.SolutionPath, "standalone", "standalone.csproj");
+            var existing = File.ReadAllText(path);
+            var updated = existing.Replace("<!-- Test Placeholder -->", content);
+            File.WriteAllText(path, updated);
+        }
+
         private static void VerifyBootManifestHashes(MSBuildResult result, string blazorPublishDirectory)
         {
             var bootManifestResolvedPath = Assert.FileExists(result, blazorPublishDirectory, "_framework", "blazor.boot.json");

src/Components/WebAssembly/Build/testassets/blazorhosted/Program.cs

@@ -10,6 +10,7 @@ namespace blazorhosted.Server
         public static void Main(string[] args)
         {
             Console.WriteLine(typeof(IWebHost));
+            GC.KeepAlive(typeof(RazorClassLibrary.Class1));
         }
     }
 }