[release/5.0.1xx-preview4] Single-File: Close AppHost stream when reu…

…sing extraction

Customer Scenario
Self-contained Apps published as a single-file fail at run-time.

Problem

Single-file bundles are now processed in the framework rather than the apphost (dotnet/runtime#34274).
This means that hostpolicy and hostfxr DLLs are excluded from being bundled themselves.
In the case of self-contained single-file apps, these files need to be separate files until static-apphost is available.
This needs to be ensured by the SDK; otherwise app execution will fail.

Solution

This change fixes the problem by adapting the SDK to:
* Pass the correct target-OS settings (otherwise cross-targetting builds will not work correctly)
* Copy files excluded by the Bundler to the publish directory.

The stage-0 netcoreapp is updated to preview4, because preview2 apphost is not compatible with preview4 bundler.

Risk
Low

global.json

@@ -1,6 +1,6 @@
 {
   "tools": {
-    "dotnet": "5.0.100-preview.2.20152.7",
+    "dotnet": "5.0.100-preview.4.20229.10",
     "runtimes": {
       "dotnet": [
         "$(MicrosoftNETCoreAppRuntimePackageVersion)"

src/Tasks/Microsoft.NET.Build.Tasks/GenerateBundle.cs

@@ -5,6 +5,8 @@
 using Microsoft.NET.HostModel.Bundle;
 using System;
 using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
 
 namespace Microsoft.NET.Build.Tasks
 {
@@ -18,13 +20,24 @@ public class GenerateBundle : TaskBase
         public bool IncludeSymbols { get; set; }
         [Required]
         public string OutputDir { get; set; }
+        [Required]
+        public string TargetFrameworkVersion { get; set; }
+        [Required]
+        public string RuntimeIdentifier { get; set; }
+
         [Required]
         public bool ShowDiagnosticOutput { get; set; }
 
+        [Output]
+        public ITaskItem[] ExcludedFiles { get; set; }
+
         protected override void ExecuteCore()
         {
+            OSPlatform targetOS = RuntimeIdentifier.StartsWith("win") ? OSPlatform.Windows :
+                                  RuntimeIdentifier.StartsWith("osx") ? OSPlatform.OSX : OSPlatform.Linux;
+
             BundleOptions options = BundleOptions.BundleAllContent | (IncludeSymbols ? BundleOptions.BundleSymbolFiles : BundleOptions.None);
-            var bundler = new Bundler(AppHostName, OutputDir, options, diagnosticOutput: ShowDiagnosticOutput);
+            var bundler = new Bundler(AppHostName, OutputDir, options, targetOS, new Version(TargetFrameworkVersion), ShowDiagnosticOutput);
             var fileSpec = new List<FileSpec>(FilesToBundle.Length);
 
             foreach (var item in FilesToBundle)
@@ -34,6 +47,12 @@ protected override void ExecuteCore()
             }
 
             bundler.GenerateBundle(fileSpec);
+
+			// Certain files are excluded from the bundle, based on BundleOptions.
+			// For example, native files and contents files are excluded by default.
+			// Return the set of excluded files in ExcludedFiles, so that they can be placed in the publish directory.
+
+            ExcludedFiles = FilesToBundle.Zip(fileSpec, (item, spec) => (spec.Excluded) ? item : null).Where(x => x != null).ToArray();
         }
     }
 }

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Publish.targets

@@ -945,11 +945,6 @@ Copyright (c) .NET Foundation. All rights reserved.
       <PublishedSingleFilePath>$(PublishDir)$(PublishedSingleFileName)</PublishedSingleFilePath>
     </PropertyGroup>
 
-    <ItemGroup>
-      <ResolvedFileToPublish Remove="@(_FilesToBundle)"/>
-      <!-- ResolvedFileToPublish shouldn't include PublishedSingleFilePath, since the single-file bundle is written directly to the publish directory -->
-    </ItemGroup>
-
   </Target>
 
   <UsingTask TaskName="GenerateBundle" AssemblyFile="$(MicrosoftNETBuildTasksAssembly)" />
@@ -963,8 +958,17 @@ Copyright (c) .NET Foundation. All rights reserved.
                     AppHostName="$(PublishedSingleFileName)"
                     IncludeSymbols="$(IncludeSymbolsInSingleFile)"
                     OutputDir="$(PublishDir)"
-                    ShowDiagnosticOutput="false"/>
+                    TargetFrameworkVersion="$(_TargetFrameworkVersionWithoutV)"
+                    RuntimeIdentifier="$(RuntimeIdentifier)"
+                    ShowDiagnosticOutput="false">
+      <Output TaskParameter="ExcludedFiles" ItemName="_FilesExcludedFromBundle"/>
+    </GenerateBundle>
 
+    <ItemGroup>
+      <ResolvedFileToPublish Remove="@(_FilesToBundle)"/>
+      <ResolvedFileToPublish Include="@(_FilesExcludedFromBundle)"/>
+      <!-- ResolvedFileToPublish shouldn't include PublishedSingleFilePath, since the single-file bundle is written directly to the publish directory -->
+    </ItemGroup>
   </Target>
 
   <!--

src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishASingleFileApp.cs

@@ -66,9 +66,9 @@ private PublishCommand GetPublishCommand()
             return new PublishCommand(Log, testAsset.TestRoot);
         }
 
-        private DirectoryInfo GetPublishDirectory(PublishCommand publishCommand)
+        private DirectoryInfo GetPublishDirectory(PublishCommand publishCommand, string targetFramework = "netcoreapp3.0")
         {
-            return publishCommand.GetOutputDirectory(targetFramework: "netcoreapp3.0",
+            return publishCommand.GetOutputDirectory(targetFramework: targetFramework,
                                                      runtimeIdentifier: RuntimeInformation.RuntimeIdentifier);
         }
 
@@ -352,5 +352,41 @@ public void It_rewrites_the_apphost_for_non_single_file_publish()
 
             appHostSize.Should().BeLessThan(singleFileSize);
         }
+
+        [CoreMSBuildOnlyTheory]
+        [InlineData("netcoreapp3.0", false)]
+        [InlineData("netcoreapp3.0", true)]
+        [InlineData("netcoreapp3.1", false)]
+        [InlineData("netcoreapp3.1", true)]
+        [InlineData("netcoreapp5.0", false)]
+        [InlineData("netcoreapp5.0", true)]
+        public void It_runs_single_file_apps(string targetFramework, bool selfContained)
+        {
+            var testProject = new TestProject()
+            {
+                Name = "SingleFileTest",
+                TargetFrameworks = targetFramework,
+                IsSdkProject = true,
+                IsExe = true,
+            };
+            testProject.AdditionalProperties.Add("SelfContained", $"{selfContained}");
+
+            var testAsset = _testAssetsManager.CreateTestProject(testProject);
+            var publishCommand = new PublishCommand(Log, Path.Combine(testAsset.TestRoot, testProject.Name));
+
+            publishCommand.Execute(PublishSingleFile, RuntimeIdentifier)
+                .Should()
+                .Pass();
+
+            var publishDir = GetPublishDirectory(publishCommand, targetFramework).FullName;
+            var singleFilePath = Path.Combine(publishDir, $"{testProject.Name}{Constants.ExeSuffix}");
+
+            var command = new RunExeCommand(Log, singleFilePath);
+            command.Execute()
+                .Should()
+                .Pass()
+                .And
+                .HaveStdOutContaining("Hello World");
+        }
     }
 }