Migrate file I/O tasks to multithreadable task API by JanProvaznik · Pull Request #12914 · dotnet/msbuild

JanProvaznik · 2025-12-10T16:21:57Z

fixes #12484
This PR migrates several file I/O tasks to use the new multithreadable task API by implementing the \IMultiThreadableTask\ interface and using \TaskEnvironment\ for thread-safe path resolution. The aim is to be maximally compatible with prior behavior in terms of where it would throw

Changes

The following tasks now implement \IMultiThreadableTask\ and use \TaskEnvironment.GetAbsolutePath()\ instead of \Path.GetFullPath():

Copy.cs
Delete.cs
MakeDir.cs
RemoveDir.cs
Touch.cs

Why

\Path.GetFullPath()\ uses process-global state (current working directory) which is not thread-safe when multiple tasks run in parallel. The \TaskEnvironment.GetAbsolutePath()\ method provides thread-safe path resolution by using the task's execution context.

This enables these tasks to be safely executed in parallel when MSBuild's multithreading is enabled.

…n status Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

…s section Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

- Updated FileState.cs to accept TaskEnvironment parameter - Migrated 7 File I/O tasks to IMultiThreadableTask: * Copy - added attribute, interface, TaskEnvironment property and updated path/environment access * Delete - migrated with proper path resolution * MakeDir - migrated with path deduplication * RemoveDir - migrated with directory operations * Touch - migrated with file timestamp operations * ReadLinesFromFile - migrated for file reading * WriteLinesToFile - migrated for file writing - All tasks use MSBuildMultiThreadableTaskAttribute for routing - All tasks implement IMultiThreadableTask for TaskEnvironment access - Tasks use TaskEnvironment.GetAbsolutePath() for thread-safe path resolution - Tasks use TaskEnvironment.GetEnvironmentVariable() for thread-safe environment access Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Copilot

Pull request overview

This PR converts several file I/O tasks to support multi-threaded execution by implementing IMultiThreadableTask and using TaskEnvironment for thread-safe path resolution. The changes replace static path resolution methods with instance-based TaskEnvironment.GetAbsolutePath() calls to ensure proper path handling in concurrent scenarios.

Key Changes:

Added IMultiThreadableTask interface and [MSBuildMultiThreadableTask] attribute to 7 file I/O task classes
Introduced TaskEnvironment property to all modified tasks for thread-safe operations
Modified FileState constructor to require TaskEnvironment parameter and use it for path resolution

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Tasks/Touch.cs	Added multithreading support; uses TaskEnvironment for path resolution in TouchFile method
src/Tasks/RemoveDir.cs	Added multithreading support; resolves paths using TaskEnvironment in Execute and RemoveDirectory methods
src/Tasks/MakeDir.cs	Added multithreading support; uses TaskEnvironment for path resolution and deduplication
src/Tasks/FileState.cs	Modified constructor to require TaskEnvironment parameter; uses it for absolute path resolution in Lazy initialization
src/Tasks/FileIO/WriteLinesToFile.cs	Added multithreading support; uses TaskEnvironment for path resolution instead of FileUtilities.NormalizePath
src/Tasks/FileIO/ReadLinesFromFile.cs	Added multithreading support; resolves file paths using TaskEnvironment before file operations
src/Tasks/Delete.cs	Added multithreading support; uses TaskEnvironment for path resolution in delete operations
src/Tasks/Copy.cs	Added multithreading support; uses TaskEnvironment for path resolution, environment variables, and FileState construction; changed PathsAreIdentical from static to instance method

src/Tasks/Copy.cs

src/Tasks/FileState.cs

src/Tasks/FileIO/WriteLinesToFile.cs

src/Tasks/RemoveDir.cs

src/Tasks/Copy.cs

AR-May

LGTM, but I would like one more review to ensure there is no behavior change in multi process mode.

src/Tasks/MakeDir.cs

src/Tasks/Copy.cs

src/Tasks/FileState.cs

src/Tasks/Delete.cs

src/Tasks/Touch.cs

src/Tasks/Copy.cs

### Context PRs #12914 and #12868 showed that we need to be able to fix and normalize `AbsolutePath`. Corresponding methods for strings live in `FileUtilities.cs` that is a Shared file and cannot reference Framework classes like `AbsolutePath`. ### Changes Made - Moved some related functions to FrameworkFileUtilities class. - Added the needed functions for `AbsolutePath` ### Testing unit tests

…#13079) ### Context PRs dotnet#12914 and dotnet#12868 showed that we need to be able to fix and normalize `AbsolutePath`. Corresponding methods for strings live in `FileUtilities.cs` that is a Shared file and cannot reference Framework classes like `AbsolutePath`. ### Changes Made - Moved some related functions to FrameworkFileUtilities class. - Added the needed functions for `AbsolutePath` ### Testing unit tests

src/Tasks/FileIO/WriteLinesToFile.cs

src/Tasks/MakeDir.cs

src/Build.UnitTests/BackEnd/TaskEnvironment_Tests.cs

src/Tasks/FileIO/ReadLinesFromFile.cs

src/Tasks/FileIO/WriteLinesToFile.cs

src/Tasks/RemoveDir.cs

src/Tasks/MakeDir.cs

src/Tasks/Delete.cs

src/Tasks/Copy.cs

YuliiaKovalova · 2026-01-26T09:38:05Z

[celebrate] Yuliia Kovalova reacted to your message:

…

________________________________ From: Jan Provazník ***@***.***> Sent: Monday, January 26, 2026 9:36:11 AM To: dotnet/msbuild ***@***.***> Cc: Yuliia Kovalova ***@***.***>; Review requested ***@***.***> Subject: Re: [dotnet/msbuild] Migrate file I/O tasks to multithreadable task API (PR #12914) Merged #12914<#12914> into main. — Reply to this email directly, view it on GitHub<#12914 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AWYM53WTVD6AU4AVU3GUXOL4IXNYXAVCNFSM6AAAAACOUJ74G2VHI2DSMVQWIX3LMV45UABCJFZXG5LFIV3GK3TUJZXXI2LGNFRWC5DJN5XDWMRSGI4DINZZGM3TOMQ>. You are receiving this because your review was requested.Message ID: ***@***.***>

### Context Migrates the Unzip task to use the `TaskEnvironment` API for thread-safe path resolution, following the pattern established in #12914. This enables the task to run safely in MSBuild's multithreaded execution model. ### Changes Made - Add `IMultiThreadableTask` interface and `[MSBuildMultiThreadableTask]` attribute to `Unzip` class - Add `TaskEnvironment` property - Replace `Path.GetFullPath()` with `TaskEnvironment.GetAbsolutePath()` for: - Destination folder creation (inside try block for proper error handling) - Source file path resolution (wrapped in try-catch to continue processing on invalid paths) - Keep `Path.GetFullPath()` in the `Extract` method for DirectoryInfo-based paths where it's cleaner - Update all unit tests to provide `TaskEnvironmentHelper.CreateForTest()` when instantiating the task ### Testing - All 14 Unzip unit tests pass - Updated all test instantiations to provide `TaskEnvironmentHelper.CreateForTest()` ### Notes - The `GetAbsolutePath` calls are wrapped in try-catch blocks to handle exceptions from invalid paths gracefully - The zip-slip exploit protection continues to use `Path.GetFullPath()` on `DirectoryInfo.FullName` as it's cleaner for paths that are already absolute   <details> <summary>Original prompt</summary> > Migrate the Unzip task to use TaskEnvironment API based on the pattern used here: #12914 > > Make sure to preserve correctness, performance and that the tests pass </details>  --- 💬 We'd love your input! Share your thoughts on Copilot coding agent in our [2 minute survey](https://gh.io/copilot-coding-agent-survey). --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

### Context Follows PR #12914 pattern. `DirectoryInfo`/`FileInfo` internally use `Path.GetFullPath()` which relies on process-global current working directory—not thread-safe when tasks run in parallel. The `TaskEnvironment.GetAbsolutePath()` API provides thread-safe path resolution using the task's execution context. ### Changes Made **ZipDirectory.cs** - Implement `IMultiThreadableTask`, add `[MSBuildMultiThreadableTask]` attribute - Add `TaskEnvironment` property - Use `TaskEnvironment.GetAbsolutePath()` to resolve paths, then create `DirectoryInfo`/`FileInfo` with the absolute path - Keep `BuildEngine3.Yield()`/`Reacquire()` calls (still needed for concurrency control) **ZipDirectory_Tests.cs** - Set `TaskEnvironment = TaskEnvironmentHelper.CreateForTest()` on all test instances ### Testing All 9 ZipDirectory tests pass. ### Notes Preserves existing behavior including error handling flow where exceptions during zip creation log an error and return via `!Log.HasLoggedErrors`. Uses `.FullName` in error messages to match original behavior.   <details> <summary>Original prompt</summary> > Migrate the ZipDirectory task to use TaskEnvironment API based on the pattern used here: #12914 > > Make sure to preserve correctness, performance and that the tests pass </details>  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.  <details> <summary>Original prompt</summary> > Migrate the DownloadFile task to use TaskEnvironment API based on the pattern used here: #12914 > > Make sure to preserve correctness, performance and that the tests pass </details>  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

### Context Migrates the Unzip task to use the `TaskEnvironment` API for thread-safe path resolution, following the pattern established in dotnet#12914. This enables the task to run safely in MSBuild's multithreaded execution model. ### Changes Made - Add `IMultiThreadableTask` interface and `[MSBuildMultiThreadableTask]` attribute to `Unzip` class - Add `TaskEnvironment` property - Replace `Path.GetFullPath()` with `TaskEnvironment.GetAbsolutePath()` for: - Destination folder creation (inside try block for proper error handling) - Source file path resolution (wrapped in try-catch to continue processing on invalid paths) - Keep `Path.GetFullPath()` in the `Extract` method for DirectoryInfo-based paths where it's cleaner - Update all unit tests to provide `TaskEnvironmentHelper.CreateForTest()` when instantiating the task ### Testing - All 14 Unzip unit tests pass - Updated all test instantiations to provide `TaskEnvironmentHelper.CreateForTest()` ### Notes - The `GetAbsolutePath` calls are wrapped in try-catch blocks to handle exceptions from invalid paths gracefully - The zip-slip exploit protection continues to use `Path.GetFullPath()` on `DirectoryInfo.FullName` as it's cleaner for paths that are already absolute   <details> <summary>Original prompt</summary> > Migrate the Unzip task to use TaskEnvironment API based on the pattern used here: dotnet#12914 > > Make sure to preserve correctness, performance and that the tests pass </details>  --- 💬 We'd love your input! Share your thoughts on Copilot coding agent in our [2 minute survey](https://gh.io/copilot-coding-agent-survey). --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

### Context Follows PR dotnet#12914 pattern. `DirectoryInfo`/`FileInfo` internally use `Path.GetFullPath()` which relies on process-global current working directory—not thread-safe when tasks run in parallel. The `TaskEnvironment.GetAbsolutePath()` API provides thread-safe path resolution using the task's execution context. ### Changes Made **ZipDirectory.cs** - Implement `IMultiThreadableTask`, add `[MSBuildMultiThreadableTask]` attribute - Add `TaskEnvironment` property - Use `TaskEnvironment.GetAbsolutePath()` to resolve paths, then create `DirectoryInfo`/`FileInfo` with the absolute path - Keep `BuildEngine3.Yield()`/`Reacquire()` calls (still needed for concurrency control) **ZipDirectory_Tests.cs** - Set `TaskEnvironment = TaskEnvironmentHelper.CreateForTest()` on all test instances ### Testing All 9 ZipDirectory tests pass. ### Notes Preserves existing behavior including error handling flow where exceptions during zip creation log an error and return via `!Log.HasLoggedErrors`. Uses `.FullName` in error messages to match original behavior.   <details> <summary>Original prompt</summary> > Migrate the ZipDirectory task to use TaskEnvironment API based on the pattern used here: dotnet#12914 > > Make sure to preserve correctness, performance and that the tests pass </details>  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.  <details> <summary>Original prompt</summary> > Migrate the DownloadFile task to use TaskEnvironment API based on the pattern used here: dotnet#12914 > > Make sure to preserve correctness, performance and that the tests pass </details>  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Copilot AI and others added 6 commits December 3, 2025 16:40

Initial plan

4bf3189

Add comprehensive spec document for threading fixes and task migratio…

101bae4

…n status Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

Update spec with race condition fix details and concurrent collection…

08bd63a

…s section Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>

remove document

40f9447

taskenvironment can't be null

7f3f946

Copilot AI review requested due to automatic review settings December 10, 2025 16:21

Copilot started reviewing on behalf of JanProvaznik December 10, 2025 16:22 View session

JanProvaznik changed the title ~~Remove null-conditional operators for TaskEnvironment in file I/O tasks~~ Migrate file I/O tasks to multithreadable task API Dec 10, 2025

JanProvaznik requested a review from AR-May December 10, 2025 16:25

Copilot AI reviewed Dec 10, 2025

View reviewed changes

JanProvaznik added 3 commits December 10, 2025 17:34

Address PR review comments: fix redundant path resolution and comments

efbdd60

Use AbsolutePath struct for type safety in file I/O tasks

9cce81f

refactoring

def225d

AR-May added the Area: Multithreaded label Dec 12, 2025

AR-May self-assigned this Dec 12, 2025

JanProvaznik added 4 commits December 16, 2025 13:09

update tests with taskenvironment

140104f

inject taskenv to all tests

1a6c0bc

fix makedir for invalid directories

7114c55

Merge branch 'main' into copilot/outline-threading-fixes-logic-updates

5fd56aa

AR-May approved these changes Dec 19, 2025

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JanProvaznik added 2 commits December 19, 2025 13:05

makedir fix optimization

7dc368c

filestate

e2b230b

JanProvaznik requested review from YuliiaKovalova and rainersigwald December 19, 2025 14:27

YuliiaKovalova reviewed Jan 6, 2026

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YuliiaKovalova reviewed Jan 6, 2026

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JanProvaznik added 3 commits January 7, 2026 12:34

pr feedback 1 - filestate, delete caching

a4a499d

revert wrong change

65f0d01

fix test

7f61524

JanProvaznik mentioned this pull request Jan 21, 2026

add OriginalValue property to AbsolutePath #13077

Merged

AR-May mentioned this pull request Jan 21, 2026

Refactor FileUtilities.cs and add methods for absolute paths. #13079

Merged

JanProvaznik added 2 commits January 21, 2026 15:37

Merge branch 'main' into copilot/outline-threading-fixes-logic-updates

4f88e63

revert

b6e238c

JanProvaznik added 2 commits January 22, 2026 13:38

align with prior behavior

b9cd8c6

Merge branch 'main' into copilot/outline-threading-fixes-logic-updates

0889314

AR-May reviewed Jan 23, 2026

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AR-May reviewed Jan 23, 2026

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rainersigwald approved these changes Jan 23, 2026

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JanProvaznik added 2 commits January 23, 2026 17:33

inheritdoc

852ace8

nits

a5de354

JanProvaznik merged commit eeb15d6 into dotnet:main Jan 26, 2026
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This was referenced Jan 27, 2026

[main] Source code updates from dotnet/msbuild dotnet/dotnet#4434

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[release/11.0.1xx-preview1] Source code updates from dotnet/msbuild dotnet/dotnet#4441

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dotnet-maestro bot mentioned this pull request Mar 3, 2026

[release/10.0.3xx] Source code updates from dotnet/msbuild dotnet/dotnet#5204

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JanProvaznik commented Dec 10, 2025 •

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