[BUG] MSYS2 fails to access Windows reparse points with IO_REPARSE_TAG_APPEXECLINK

[saschanaz]

Describe the bug

MSYS shell fails to run UWP apps with "Permission denied" error.

Steps to Reproduce the Problem

1. Install MSYS2 from https://www.msys2.org/
2. Install Python 3 from https://www.microsoft.com/store/productId/9MSSZTT1N39L
3. Run /c/Users/Kagami/AppData/Local/Microsoft/WindowsApps/python3.exe from MSYS2

Expected behavior: It should run Python 3

Additional Context: Operating System, Screenshots

If applicable, add screenshots to help explain your problem.

• OS: Windows 10 Pro version 2004 64bit

UWP apps creates reparse points for their executables in /c/Users/Kagami/AppData/Local/Microsoft/WindowsApps/, while MSYS fails to reparse them.

See the PowerShell side of patch: PowerShell/PowerShell#10331

[Biswa96]

Read the error carefully. It says "Permission denied". Windows UWP realm is restricted from outer world unless the developer adds the permission in AppxManifest file, like Windows Terminal does.

[saschanaz]

Windows UWP realm is restricted from outer world unless the developer adds the permission in AppxManifest file

I think that mainly applies when the UWP app wants to access the system, not vise versa. Especially when cmd and pwsh can just access it.

[saschanaz]

Added more details that show this is an MSYS bug.

[saschanaz]

It seems this part should be fixed to support the new tag.

https://github.com/msys2/Cygwin/blob/master/winsup/cygwin/path.cc#L2534-L2618

Edit: Okay, this is a cygwin bug.