fs APIs don't understand AppExecLink reparse points on Windows

[TylerLeonhardt]

• Version: v14.15.3
• Platform: Windows
• Subsystem: fs

What steps will reproduce the bug?

1. Install an app from the Microsoft Store like PowerShell, PowerShell Preview, or Python.
2. Run the following in Node.js:

// 1
fs.statSync("C:\\Users\\tyleonha\\AppData\\Local\\Microsoft\\WindowsApps\\pwsh.exe")

// 2
fs.existsSync("C:\\Users\\tyleonha\\AppData\\Local\\Microsoft\\WindowsApps\\pwsh.exe")

How often does it reproduce? Is there a required condition?

100% repro rate

What is the expected behavior?

// 1
Stats {
  dev: 2191433689,
  mode: 33206,
  nlink: 1,
  uid: 0,
  gid: 0,
  rdev: 0,
  blksize: 4096,
  ino: 2251799813690117,
  size: 6,
  blocks: 0,
  atimeMs: 1609796639210.8977,
  mtimeMs: 1609794509320.4253,
  ctimeMs: 1609794563739.3364,
  birthtimeMs: 1609794509315.4263,
  atime: 2021-01-04T21:43:59.211Z,
  mtime: 2021-01-04T21:08:29.320Z,
  ctime: 2021-01-04T21:09:23.739Z,
  birthtime: 2021-01-04T21:08:29.315Z
}

// 2
true

What do you see instead?

// 1
Uncaught:
Error: EACCES: permission denied, stat 'C:\Users\tyleonha\AppData\Local\Microsoft\WindowsApps\pwsh.exe'
    at Object.statSync (fs.js:1086:3) {
  errno: -4092,
  syscall: 'stat',
  code: 'EACCES',
  path: 'C:\\Users\\tyleonha\\AppData\\Local\\Microsoft\\WindowsApps\\pwsh.exe'
}

// 2
false

Additional information

This only seems to happen with AppExecLink reparse points on Windows. Regular SymbolicLinks are fine on Windows and give the expected behavior.

Also, fs.lstatSync works with these AppExecLink's which I'm guessing is because lstat operates on the symlnk and not the file that the symlnk points to.

Related issues:
#33024
microsoft/vscode#95828

[TylerLeonhardt]

This appears to be a workaround (using fs.readlinkSync):

> fs.statSync(fs.readlinkSync("C:\\Users\\tyleonha\\AppData\\Local\\Microsoft\\WindowsApps\\pwsh.exe"))

Stats {
  dev: 2191433689,
  mode: 33206,
  nlink: 1,
  uid: 0,
  gid: 0,
  rdev: 0,
  blksize: 4096,
  ino: 562949953571058,
  size: 280456,
  blocks: 552,
  atimeMs: 1609813951771.307,
  mtimeMs: 1606342749993.0173,
  ctimeMs: 1606360363788.224,
  birthtimeMs: 1606342735014.0168,
  atime: 2021-01-05T02:32:31.771Z,
  mtime: 2020-11-25T22:19:09.993Z,
  ctime: 2020-11-26T03:12:43.788Z,
  birthtime: 2020-11-25T22:18:55.014Z
}

[jasnell]

The fs.readlinkSync workaround is likely just giving you the details of the SystemUDPLauncher.exe and not the pwsh.exe file here. Hmm... definitely thinking this is something that needs to be fixed at the libuv level.

/cc @nodejs/libuv

[vtjnash]

It throws EACCES, because Win32 as apparently designed, forbids access to stat on this file #33024 (comment). Perhaps something like https://github.com/libuv/libuv/pull/3268/files#r1007238152 would work though.