Add build-time guard for Windows long path support (#49028)

PowerToys has deeply nested source paths that exceed the legacy
260-character MAX_PATH limit. Contributors who haven't enabled Windows
long path support hit cryptic 'path too long' / 'could not find file'
errors during their first build.

Add an EnsureLongPathsEnabled MSBuild target in Directory.Build.targets
that reads
HKLM\SYSTEM\CurrentControlSet\Control\FileSystem\LongPathsEnabled and
fails fast with an actionable error (PTLONGPATH) pointing at
tools\build\setup-dev-environment.ps1. Covers both Visual Studio and the
command-line build scripts, skips design-time builds, and can be
bypassed with /p:SkipLongPathsCheck=true.

**What happens if Long file path isn't enabled.**
<img width="824" height="916" alt="image"
src="https://github.com/user-attachments/assets/30731f65-4011-48c0-94b9-e521b4c7d266"
/>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This commit is contained in:
Clint Rutkas
2026-06-29 14:29:14 -07:00
committed by GitHub
parent b73fd670be
commit 7b19b4c219

View File

@@ -4,6 +4,29 @@
<Import Project="$(MSBuildCachePackageRoot)\build\$(MSBuildCachePackageName).targets" Condition="'$(MSBuildCacheEnabled)' == 'true'" />
<Import Project="$(MSBuildCacheSharedCompilationPackageRoot)\build\Microsoft.MSBuildCache.SharedCompilation.targets" Condition="'$(MSBuildCacheEnabled)' == 'true'" />
<!--
Onboarding guard: PowerToys has deeply nested source paths that exceed the legacy
260-character MAX_PATH limit. Without Windows long path support enabled, the build
fails with cryptic "path too long" / "could not find file" errors that are hard for
new contributors to diagnose. Detect the missing registry setting up front and emit a
clear, actionable error before the confusing failures occur.
- Covers both Visual Studio (Ctrl+Shift+B) and the command-line build scripts.
- Runs only during real builds (skips design-time/IntelliSense passes).
- Bypass with /p:SkipLongPathsCheck=true if you know what you're doing.
See tools\build\setup-dev-environment.ps1 to enable everything automatically.
-->
<Target Name="EnsureLongPathsEnabled"
BeforeTargets="PrepareForBuild"
Condition="'$(DesignTimeBuild)' != 'true' and '$(SkipLongPathsCheck)' != 'true' and '$(OS)' == 'Windows_NT'">
<PropertyGroup>
<_LongPathsEnabled>$([MSBuild]::GetRegistryValueFromView('HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem', 'LongPathsEnabled', null, RegistryView.Registry64))</_LongPathsEnabled>
</PropertyGroup>
<Error Condition="'$(_LongPathsEnabled)' != '1'"
Code="PTLONGPATH"
Text="Windows long path support is not enabled. PowerToys source paths exceed the 260-character MAX_PATH limit, so the build will fail with cryptic 'path too long' errors. Fix it by running (from an elevated PowerShell): .\tools\build\setup-dev-environment.ps1 -- or set HKLM\SYSTEM\CurrentControlSet\Control\FileSystem\LongPathsEnabled = 1 (DWORD) and restart Windows. To bypass this check, build with /p:SkipLongPathsCheck=true." />
</Target>
<!-- Override ManifestTool to the x64 host tool under WindowsSdkDir for all projects once the SDK path is known. -->
<PropertyGroup Label="ManifestToolOverride">
<ManifestTool Condition="Exists('$(WindowsSdkDir)bin\x64\mt.exe')">$(WindowsSdkDir)bin\x64\mt.exe</ManifestTool>