Multithreading migration: Group 7 — 4 attribute-only + 2 Pattern B tasks

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

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using FluentAssertions;
+using Microsoft.Build.Framework;
+using System.Collections.Concurrent;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace Microsoft.NET.Build.Tasks.UnitTests
+{
+    public class GivenAFilterResolvedFilesMultiThreading
+    {
+        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": {} }
+              }
+            }
+            """;
+
+        [Fact]
+        public void FilterResolvedFiles_HasMultiThreadableAttribute()
+        {
+            typeof(FilterResolvedFiles).GetCustomAttribute<MSBuildMultiThreadableTaskAttribute>()
+                .Should().NotBeNull("task must be decorated with [MSBuildMultiThreadableTask]");
+        }
+
+        [Fact]
+        public void AssetsFilePath_IsResolvedRelativeToProjectDirectory()
+        {
+            var projectDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"filter-mt-{Guid.NewGuid():N}"));
+            Directory.CreateDirectory(projectDir);
+            try
+            {
+                var assetsDir = Path.Combine(projectDir, "obj");
+                Directory.CreateDirectory(assetsDir);
+                File.WriteAllText(Path.Combine(assetsDir, "project.assets.json"), AssetsJson);
+
+                var task = new FilterResolvedFiles
+                {
+                    BuildEngine = new MockBuildEngine(),
+                    AssetsFilePath = "obj\\project.assets.json",
+                    ResolvedFiles = Array.Empty<ITaskItem>(),
+                    PackagesToPrune = Array.Empty<ITaskItem>(),
+                    TargetFramework = ".NETCoreApp,Version=v8.0",
+                    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);
+            }
+        }
+
+        private static (bool result, MockBuildEngine engine) RunTask(
+            string assetsRelPath, string projectDir)
+        {
+            var engine = new MockBuildEngine();
+            var task = new FilterResolvedFiles
+            {
+                BuildEngine = engine,
+                AssetsFilePath = assetsRelPath,
+                ResolvedFiles = Array.Empty<ITaskItem>(),
+                PackagesToPrune = Array.Empty<ITaskItem>(),
+                TargetFramework = ".NETCoreApp,Version=v8.0",
+                TaskEnvironment = TaskEnvironmentHelper.CreateForTest(projectDir),
+            };
+
+            var result = task.Execute();
+            return (result, engine);
+        }
+
+        [Fact]
+        public void ItProducesSameResultsInMultiProcessAndMultiThreadedEnvironments()
+        {
+            var projectDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"filter-parity-{Guid.NewGuid():N}"));
+            var otherDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"filter-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");
+                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);
+            }
+        }
+
+        [Theory]
+        [InlineData(4)]
+        [InlineData(16)]
+        public void FilterResolvedFiles_ConcurrentExecution(int parallelism)
+        {
+            var projectDir = Path.GetFullPath(Path.Combine(Path.GetTempPath(), $"filter-concurrent-{Guid.NewGuid():N}"));
+            Directory.CreateDirectory(projectDir);
+            try
+            {
+                var objDir = Path.Combine(projectDir, "obj");
+                Directory.CreateDirectory(objDir);
+                File.WriteAllText(Path.Combine(objDir, "project.assets.json"), AssetsJson);
+
+                var errors = new ConcurrentBag<string>();
+                var barrier = new Barrier(parallelism);
+                Parallel.For(0, parallelism, new ParallelOptions { MaxDegreeOfParallelism = parallelism }, i =>
+                {
+                    try
+                    {
+                        var task = new FilterResolvedFiles
+                        {
+                            BuildEngine = new MockBuildEngine(),
+                            AssetsFilePath = Path.Combine("obj", "project.assets.json"),
+                            ResolvedFiles = Array.Empty<ITaskItem>(),
+                            PackagesToPrune = Array.Empty<ITaskItem>(),
+                            TargetFramework = ".NETCoreApp,Version=v8.0",
+                            TaskEnvironment = TaskEnvironmentHelper.CreateForTest(projectDir),
+                        };
+                        barrier.SignalAndWait();
+                        task.Execute();
+                    }
+                    catch (Exception ex) { errors.Add($"Thread {i}: {ex.Message}"); }
+                });
+                errors.Should().BeEmpty();
+            }
+            finally
+            {
+                Directory.Delete(projectDir, true);
+            }
+        }
+    }
+}