Multithreading migration: Group 7 — 4 attribute-only + 2 Pattern B tasks by SimaTian · Pull Request #53118 · dotnet/sdk

SimaTian · 2026-02-22T20:01:12Z

Summary

Migrate 5 tasks to support multithreaded MSBuild execution. Three tasks are attribute-only (Pattern A), two require interface-based migration (Pattern B).

Tasks Migrated

Task	Pattern	Key Changes
SetGeneratedAppConfigMetadata	A	Attribute added; behavioral tests
ValidateExecutableReferences	A	Attribute added; behavioral tests
RemoveDuplicatePackageReferences	A	Attribute already on main; tests added
SelectRuntimeIdentifierSpecificItems	B	Added `IMultiThreadableTask`, `TaskEnvironment`; absolutized `RuntimeIdentifierGraphPath`
FilterResolvedFiles	B	Added `IMultiThreadableTask`, `TaskEnvironment`; absolutized `AssetsFilePath`

Pattern B Details

SelectRuntimeIdentifierSpecificItems: Calls RuntimeGraphCache.GetRuntimeGraph(RuntimeIdentifierGraphPath) which enforces Path.IsPathRooted() and performs file I/O via JsonRuntimeFormat.ReadRuntimeGraph(). RuntimeIdentifierGraphPath is absolutized via TaskEnvironment.GetAbsolutePath() before the call.

FilterResolvedFiles: Calls LockFileCache.GetLockFile(AssetsFilePath) which requires rooted paths. AssetsFilePath is absolutized before the call.

Tests Added

GivenAttributeOnlyTasksGroup7.cs — attribute-presence tests, behavioral tests, parity tests, concurrent execution tests
GivenAFilterResolvedFilesMultiThreading.cs — CWD-independence parity test, path resolution test

Files Changed

src/Tasks/Microsoft.NET.Build.Tasks/SelectRuntimeIdentifierSpecificItems.cs
src/Tasks/Microsoft.NET.Build.Tasks/SetGeneratedAppConfigMetadata.cs
src/Tasks/Microsoft.NET.Build.Tasks/ValidateExecutableReferences.cs
src/Tasks/Microsoft.NET.Build.Tasks/FilterResolvedFiles.cs
src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAttributeOnlyTasksGroup7.cs (new)
src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAFilterResolvedFilesMultiThreading.cs (new)

Tasks: SelectRuntimeIdentifierSpecificItems, SetGeneratedAppConfigMetadata, ValidateExecutableReferences, FilterResolvedFiles, RemoveDuplicatePackageReferences. FilterResolvedFiles includes absolutization of AssetsFilePath. Others are attribute-only with test additions. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

… (Group 7) Add [MSBuildMultiThreadableTask] attribute verification for 4 attribute-only tasks plus FilterResolvedFiles. Replace reflection-based TaskEnvironment assignment with direct property access. Add parity test for FilterResolvedFiles verifying CWD-independent behavior. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…file The test was misplaced (FilterResolvedFiles is Pattern B, not attribute-only) and had a latent NullReferenceException bug due to missing TaskEnvironment assignment. The correct version exists in GivenAFilterResolvedFilesMultiThreading.cs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Task calls RuntimeGraphCache.GetRuntimeGraph(RuntimeIdentifierGraphPath) which does file I/O (JsonRuntimeFormat.ReadRuntimeGraph). The path must be absolutized via TaskEnvironment for multithreading safety. Changes: - Add IMultiThreadableTask interface and TaskEnvironment property - Absolutize RuntimeIdentifierGraphPath before passing to RuntimeGraphCache - Update tests to provide TaskEnvironment via TaskEnvironmentHelper.CreateForTest Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Migrates a set of Microsoft.NET.Build.Tasks MSBuild tasks to support multithreaded execution by adding the multithreadable task attribute and, for Pattern B tasks, implementing IMultiThreadableTask and resolving file paths via TaskEnvironment.

Changes:

Added [MSBuildMultiThreadableTask] to attribute-only tasks (SetGeneratedAppConfigMetadata, ValidateExecutableReferences).
Updated Pattern B tasks (SelectRuntimeIdentifierSpecificItems, FilterResolvedFiles) to implement IMultiThreadableTask and resolve input file paths using TaskEnvironment.GetAbsolutePath.
Added new unit tests validating attribute presence, CWD-independence/parity, and concurrent execution behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Tasks/Microsoft.NET.Build.Tasks/ValidateExecutableReferences.cs	Marks the task as multithreadable (attribute-only).
src/Tasks/Microsoft.NET.Build.Tasks/SetGeneratedAppConfigMetadata.cs	Marks the task as multithreadable (attribute-only).
src/Tasks/Microsoft.NET.Build.Tasks/SelectRuntimeIdentifierSpecificItems.cs	Implements `IMultiThreadableTask` and resolves `RuntimeIdentifierGraphPath` via `TaskEnvironment`.
src/Tasks/Microsoft.NET.Build.Tasks/FilterResolvedFiles.cs	Implements `IMultiThreadableTask` and resolves `AssetsFilePath` via `TaskEnvironment`.
src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAttributeOnlyTasksGroup7.cs	Adds attribute presence, behavioral/parity, and concurrency tests for the migrated tasks.
src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAFilterResolvedFilesMultiThreading.cs	Adds tests for `FilterResolvedFiles` attribute presence, path resolution, parity, and concurrency.

Copilot · 2026-02-22T20:06:18Z

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

+                {
+                    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),
+                };


AssetsFilePath is set to a Windows-specific relative string ("obj\project.assets.json"). On non-Windows this becomes a filename containing a backslash, so TaskEnvironment.GetAbsolutePath will resolve to a path that doesn’t exist and the test will fail. Use Path.Combine("obj", "project.assets.json") (or "obj/project.assets.json") so the test is OS-agnostic.

Copilot · 2026-02-22T20:06:18Z

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

+                            TaskEnvironment = TaskEnvironmentHelper.CreateForTest(projectDir),
+                        };
+                        barrier.SignalAndWait();
+                        task.Execute();


The concurrent execution test ignores the return value from task.Execute(). If the task starts logging errors (and returns false) without throwing, this test would still pass. Capture/assert the result (and optionally assert no logged errors) so the test actually validates successful concurrent execution.

Suggested change

task.Execute();

var result = task.Execute();

if (!result)

{

errors.Add($"Thread {i}: task.Execute returned false");

}

Copilot · 2026-02-22T20:06:18Z

src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAttributeOnlyTasksGroup7.cs

+                        TargetRuntimeIdentifier = "linux-x64",
+                        Items = new ITaskItem[]
+                        {
+                            CreateItemWithRid($"Item{i}", "linux-x64")
+                        },
+                        RuntimeIdentifierGraphPath = ""
+                    };
+                    barrier.SignalAndWait();
+                    task.Execute();
+                }


RuntimeIdentifierGraphPath is set to an empty string in this test. TaskEnvironmentHelper ultimately constructs an AbsolutePath and will throw for null/empty paths, so this concurrent execution test will consistently fail. Create/write a real runtime graph file (like the earlier parity test) and pass its path here.

Copilot · 2026-02-22T20:06:19Z

src/Tasks/Microsoft.NET.Build.Tasks.UnitTests/GivenAttributeOnlyTasksGroup7.cs

+        public void SetGeneratedAppConfigMetadata_ConcurrentExecution(int parallelism)
+        {
+            var errors = new ConcurrentBag<string>();
+            var barrier = new Barrier(parallelism);
+            Parallel.For(0, parallelism, new ParallelOptions { MaxDegreeOfParallelism = parallelism }, i =>
+            {
+                try
+                {
+                    var task = new SetGeneratedAppConfigMetadata
+                    {
+                        BuildEngine = new MockBuildEngine(),
+                        GeneratedAppConfigFile = $"obj/app{i}.exe.config",
+                        TargetName = $"app{i}.exe.config"
+                    };
+                    barrier.SignalAndWait();
+                    task.Execute();
+                }
+                catch (Exception ex) { errors.Add($"Thread {i}: {ex.Message}"); }
+            });
+            errors.Should().BeEmpty();
+        }
+
+        [Theory]
+        [InlineData(4)]
+        [InlineData(16)]
+        public void ValidateExecutableReferences_ConcurrentExecution(int parallelism)
+        {
+            var errors = new ConcurrentBag<string>();
+            var barrier = new Barrier(parallelism);
+            Parallel.For(0, parallelism, new ParallelOptions { MaxDegreeOfParallelism = parallelism }, i =>
+            {
+                try
+                {
+                    var task = new ValidateExecutableReferences
+                    {
+                        BuildEngine = new MockBuildEngine(),
+                        IsExecutable = false,
+                        SelfContained = false,
+                        ReferencedProjects = Array.Empty<ITaskItem>()
+                    };
+                    barrier.SignalAndWait();
+                    task.Execute();
+                }
+                catch (Exception ex) { errors.Add($"Thread {i}: {ex.Message}"); }
+            });
+            errors.Should().BeEmpty();
+        }
+
+        [Theory]
+        [InlineData(4)]
+        [InlineData(16)]
+        public void RemoveDuplicatePackageReferences_ConcurrentExecution(int parallelism)
+        {
+            var errors = new ConcurrentBag<string>();
+            var barrier = new Barrier(parallelism);
+            Parallel.For(0, parallelism, new ParallelOptions { MaxDegreeOfParallelism = parallelism }, i =>
+            {
+                try
+                {
+                    var task = new RemoveDuplicatePackageReferences
+                    {
+                        BuildEngine = new MockBuildEngine(),
+                        InputPackageReferences = new ITaskItem[]
+                        {
+                            new MockTaskItem($"Package{i}", new Dictionary<string, string> { { "Version", "1.0.0" } })
+                        }
+                    };
+                    barrier.SignalAndWait();
+                    task.Execute();
+                }
+                catch (Exception ex) { errors.Add($"Thread {i}: {ex.Message}"); }
+            });
+            errors.Should().BeEmpty();
+        }


These concurrent execution tests call task.Execute() but don’t assert the returned value. If a task logs errors and returns false (without throwing), the test would still pass and mask failures. Assert Execute() returns true (and/or validate the mock build engine has no errors) inside the loop.

Copilot · 2026-02-22T20:06:19Z

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

        protected override void ExecuteCore()
        {
            var lockFileCache = new LockFileCache(this);
-            LockFile lockFile = lockFileCache.GetLockFile(AssetsFilePath);
+            LockFile lockFile = lockFileCache.GetLockFile(TaskEnvironment.GetAbsolutePath(AssetsFilePath));



ExecuteCore unconditionally dereferences TaskEnvironment and calls GetAbsolutePath. If TaskEnvironment isn’t injected (e.g., task instantiated outside MSBuild, or an older host that doesn’t set it), this becomes a NullReferenceException that rethrows from TaskBase.Execute() rather than a logged build error. Consider guarding against null (and falling back to the original AssetsFilePath / logging a clear error) to avoid hard crashes.

… fix - Replace Barrier+Parallel.For with ManualResetEventSlim+Task.Run - Use async test methods with Task.WhenAll - Replace Windows path separator with Path.Combine - Fix empty RuntimeIdentifierGraphPath in concurrent test - Assert Execute() return value in concurrent tests Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add TaskEnvironmentDefaults.cs for NETFRAMEWORK lazy-init fallback - Apply lazy-init pattern to FilterResolvedFiles Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The combining constructor AbsolutePath(string, AbsolutePath) used Path.Combine without Path.GetFullPath, leaving '..' segments unresolved. This caused output paths like 'dir\..\ClassLib\...' instead of 'ClassLib\...', breaking string-based path comparisons in downstream MSBuild targets and tests. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

On .NET Framework, ProcessStartInfo defaults to UseShellExecute=true, which prevents EnvironmentVariables from being applied. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Normalization is caller's responsibility, matching real MSBuild polyfill. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Use assembly-relative path instead of bare filename to avoid FileNotFound when parallel tests change the process CWD via TaskTestEnvironment. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…y-init and set TaskEnvironment in tests - Replace '= null!' with #if NETFRAMEWORK lazy-init pattern for TaskEnvironment property, matching all other Pattern B tasks - Set TaskEnvironment in all 5 test instantiations to prevent NRE on .NET Core where there is no lazy-init fallback Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

SimaTian and others added 5 commits February 22, 2026 16:29

Add concurrent execution tests for Group 7 tasks

f298249

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings February 22, 2026 20:01

Copilot started reviewing on behalf of SimaTian February 22, 2026 20:01 View session

Copilot AI reviewed Feb 22, 2026

View reviewed changes

SimaTian self-assigned this Feb 23, 2026

SimaTian requested a review from JanProvaznik February 23, 2026 14:14

SimaTian and others added 2 commits February 23, 2026 17:12

Fix CWD race: add [Collection] to serialize CWD-mutating tests

aae3335

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add TaskEnvironment lazy-init for merge-group-7 tasks

aae3ef3

- Add TaskEnvironmentDefaults.cs for NETFRAMEWORK lazy-init fallback - Apply lazy-init pattern to FilterResolvedFiles Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

build-analysis bot mentioned this pull request Feb 24, 2026

Template engine tests hitting known parallelism issue in GetVisualStudioInstances #44878

Open

SimaTian marked this pull request as draft February 24, 2026 17:54

SimaTian and others added 4 commits February 25, 2026 13:20

Add UseShellExecute=false in ProcessTaskEnvironmentDriver

c93afc4

On .NET Framework, ProcessStartInfo defaults to UseShellExecute=true, which prevents EnvironmentVariables from being applied. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Revert AbsolutePath: remove Path.GetFullPath wrapping

228c57a

Normalization is caller's responsibility, matching real MSBuild polyfill. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Fix CWD-dependent Strings.resx loading in GivenThatWeHaveErrorCodes

a8f097c

Use assembly-relative path instead of bare filename to avoid FileNotFound when parallel tests change the process CWD via TaskTestEnvironment. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Multithreading migration: Group 7 — 4 attribute-only + 2 Pattern B tasks#53118

Multithreading migration: Group 7 — 4 attribute-only + 2 Pattern B tasks#53118
SimaTian wants to merge 13 commits intodotnet:mainfrom
SimaTian:merge-group-7

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-                        task.Execute();
+                        var result = task.Execute();
+                        if (!result)
+                        {
+                            errors.Add($"Thread {i}: task.Execute returned false");
+                        }

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SimaTian commented Feb 22, 2026

Summary

Tasks Migrated

Pattern B Details

Tests Added

Files Changed

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Pull request overview

Reviewed changes

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