fs.mkdir recursive edge case potential issues #25110

• Version: v10.14.2
• Platform: Linux lt2 4.19.8-200.fc28.x86_64 deps: update openssl to 1.0.1j #1 SMP Mon Dec 10 15:43:40 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem: fs

Example Code:

const fs = require('fs');
fs.mkdirSync('/', {recursive: true, mode: 0o777});

• In Windows this results in an EPERM exception.
• On my Linux system this does not attempt to chmod the existing path, it reports success as the path already exists even though the mode is wrong.

The same occurs with fs.mkdir, I used fs.mkdirSync in the example as the code is simpler.

I've uncovered these edge cases via sindresorhus/make-dir#7 where I'm working on making that module use the native recursive mkdir when possible. The plan is for make-dir@2 to emulate the native fs.mkdir recursive for older versions of node, so I'm hoping for clarification on these two potential issues.

CC @bcoe