Multithreading migration: Group 9 — 4 Package/Asset tasks (Pattern B)

src/Tasks/Common/ProcessTaskEnvironmentDriver.cs

@@ -103,6 +103,7 @@ public ProcessStartInfo GetProcessStartInfo()
             var startInfo = new ProcessStartInfo
             {
                 WorkingDirectory = _projectDirectory.Value,
+                UseShellExecute = false,
             };
 
             // Populate environment from the scoped environment dictionary

src/Tasks/Common/TaskEnvironmentDefaults.cs

@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Provides a default TaskEnvironment for single-threaded MSBuild execution.
+// When MSBuild supports IMultiThreadableTask, it sets TaskEnvironment directly.
+// This fallback ensures tasks work with older MSBuild versions that do not set it.
+
+#if NETFRAMEWORK
+
+using System;
+
+namespace Microsoft.Build.Framework
+{
+    internal static class TaskEnvironmentDefaults
+    {
+        /// <summary>
+        /// Creates a default TaskEnvironment backed by the current process environment.
+        /// Uses Environment.CurrentDirectory as the project directory, which in single-threaded
+        /// MSBuild is set to the project directory before task execution.
+        /// </summary>
+        internal static TaskEnvironment Create() =>
+            new TaskEnvironment(new ProcessTaskEnvironmentDriver(Environment.CurrentDirectory));
+    }
+}
+
+#endif

src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAGetPackageDirectoryMultiThreading.cs

@@ -0,0 +1,165 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Concurrent;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Build.Framework;
+using Xunit;
+
+namespace Microsoft.NET.Build.Tasks.UnitTests
+{
+    [Collection("CWD-Dependent")]
+
+    public class GivenAGetPackageDirectoryMultiThreading
+    {
+        private const string AssetsJson = """
+            {
+              "version": 3,
+              "targets": { ".NETCoreApp,Version=v8.0": {} },
+              "libraries": {},
+              "packageFolders": {},
+              "projectFileDependencyGroups": { ".NETCoreApp,Version=v8.0": [] },
+              "project": {
+                "version": "1.0.0",
+                "frameworks": { "net8.0": {} }
+              }
+            }
+            """;
+
+        private static (bool result, MockBuildEngine engine) RunTask(
+            string assetsRelPath, string projectDir)
+        {
+            var engine = new MockBuildEngine();
+            var task = new GetPackageDirectory
+            {
+                BuildEngine = engine,
+                AssetsFileWithAdditionalPackageFolders = assetsRelPath,
+                Items = Array.Empty<ITaskItem>(),
+                PackageFolders = Array.Empty<string>(),
+                TaskEnvironment = TaskEnvironmentHelper.CreateForTest(projectDir),
+            };
+
+            var result = task.Execute();
+            return (result, engine);
+        }
+
+        [Fact]
+        public void AssetsFile_IsResolvedRelativeToProjectDirectory()
+        {
+            var projectDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"pkgdir-mt-{Guid.NewGuid():N}"));
+            Directory.CreateDirectory(projectDir);
+            try
+            {
+                var objDir = Path.Combine(projectDir, "obj");
+                Directory.CreateDirectory(objDir);
+                File.WriteAllText(Path.Combine(objDir, "project.assets.json"), AssetsJson);
+
+                var task = new GetPackageDirectory
+                {
+                    BuildEngine = new MockBuildEngine(),
+                    AssetsFileWithAdditionalPackageFolders = "obj\\project.assets.json",
+                    Items = Array.Empty<ITaskItem>(),
+                    PackageFolders = Array.Empty<string>(),
+                };
+
+                var teProp = task.GetType().GetProperty("TaskEnvironment");
+                teProp.Should().NotBeNull("task must have a TaskEnvironment property after migration");
+                task.TaskEnvironment = TaskEnvironmentHelper.CreateForTest(projectDir);
+
+                var result = task.Execute();
+                result.Should().BeTrue("task should succeed when assets file is found via TaskEnvironment");
+            }
+            finally
+            {
+                Directory.Delete(projectDir, true);
+            }
+        }
+
+        [Theory]
+        [InlineData(4)]
+        [InlineData(16)]
+        public void GetPackageDirectory_ConcurrentExecution(int parallelism)
+        {
+            var projectDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"pkgdir-conc-{Guid.NewGuid():N}"));
+            Directory.CreateDirectory(projectDir);
+            try
+            {
+                var objDir = Path.Combine(projectDir, "obj");
+                Directory.CreateDirectory(objDir);
+                File.WriteAllText(Path.Combine(objDir, "project.assets.json"), AssetsJson);
+
+                var errors = new ConcurrentBag<string>();
+                var barrier = new Barrier(parallelism);
+                Parallel.For(0, parallelism, new ParallelOptions { MaxDegreeOfParallelism = parallelism }, i =>
+                {
+                    try
+                    {
+                        var task = new GetPackageDirectory
+                        {
+                            BuildEngine = new MockBuildEngine(),
+                            TaskEnvironment = TaskEnvironmentHelper.CreateForTest(projectDir),
+                            AssetsFileWithAdditionalPackageFolders = Path.Combine("obj", "project.assets.json"),
+                            Items = Array.Empty<ITaskItem>(),
+                            PackageFolders = Array.Empty<string>(),
+                        };
+                        barrier.SignalAndWait();
+                        task.Execute();
+                    }
+                    catch (Exception ex) { errors.Add($"Thread {i}: {ex.Message}"); }
+                });
+                errors.Should().BeEmpty();
+            }
+            finally
+            {
+                Directory.Delete(projectDir, true);
+            }
+        }
+
+        [Fact]
+        public void ItProducesSameResultsInMultiProcessAndMultiThreadedEnvironments()
+        {
+            var projectDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"pkgdir-parity-{Guid.NewGuid():N}"));
+            var otherDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"pkgdir-decoy-{Guid.NewGuid():N}"));
+            Directory.CreateDirectory(projectDir);
+            Directory.CreateDirectory(otherDir);
+            var savedCwd = Directory.GetCurrentDirectory();
+            try
+            {
+                var objDir = Path.Combine(projectDir, "obj");
+                Directory.CreateDirectory(objDir);
+                File.WriteAllText(Path.Combine(objDir, "project.assets.json"), AssetsJson);
+
+                var assetsRelPath = Path.Combine("obj", "project.assets.json");
+
+                // --- Multiprocess mode: CWD == projectDir ---
+                Directory.SetCurrentDirectory(projectDir);
+                var (mpResult, mpEngine) = RunTask(assetsRelPath, projectDir);
+
+                // --- Multithreaded mode: CWD == otherDir ---
+                Directory.SetCurrentDirectory(otherDir);
+                var (mtResult, mtEngine) = RunTask(assetsRelPath, projectDir);
+
+                mpResult.Should().Be(mtResult,
+                    "task should return the same success/failure in both environments");
+                mpEngine.Errors.Count.Should().Be(mtEngine.Errors.Count,
+                    "error count should be the same in both environments");
+                for (int i = 0; i < mpEngine.Errors.Count; i++)
+                {
+                    mpEngine.Errors[i].Message.Should().Be(
+                        mtEngine.Errors[i].Message,
+                        $"error message [{i}] should be identical in both environments");
+                }
+                mpEngine.Warnings.Count.Should().Be(mtEngine.Warnings.Count,
+                    "warning count should be the same in both environments");
+            }
+            finally
+            {
+                Directory.SetCurrentDirectory(savedCwd);
+                Directory.Delete(projectDir, true);
+                if (Directory.Exists(otherDir)) Directory.Delete(otherDir, true);
+            }
+        }
+    }
+}