Inconsistent results for path.toNamespacedPath() for win32 UNC paths

[btsimonh]

• Version: v12.10.0
• Platform: windows 10 64 bit
• Subsystem: path/fs

when using UNC paths, the function path.toNamespacedPath() gives different results from non UNC paths.

This is reproduced by running the code attached below.
Basically, most of the time in Node, you can freely use '/' and '', and most repos just use '/', for example this snippet:
fs.readdirSync(__dirname + '/grant').forEach(function(filename) {
from
https://github.com/jaredhanson/oauth2orize/blob/master/lib/index.js

The issue is that if the path being accessed is a UNC style (actually, problem is only if accessed pre-namespaced?) path, then the '/' does not get translated to a '' on windows. If the path is a 'normal' drive based windows path, then the '/' is replaced by '' in path.toNamespacedPath(), which is used by most fs functions to qualify a path, and so there is no issue.

As you can see from the results of the simple tests, path.win32.resolve('\\?\c:\Windows/System') returns '\\?\c:\Windows\System'.
path.toNamespacedPath(path) uses this internally, but returns path, not resolvedPath in this circumstance. So the resulting path from path.toNamespacedPath('\\?\c:\Windows/System') is '\\?\c:\Windows/System' - which is invalid.
(I will post a proposed solution in the next comment).

Simple example test:

on a windows system, run the following code:

var tests = [
  'c:\\Windows\\System',
  'c:\\Windows/System',
  '\\\\?\\c:\\Windows\\System',
  '\\\\?\\c:\\Windows/System',
]

var path = require('path');
var fs = require('fs');

for (var i = 0; i < tests.length; i++) {
  console.log('path.toNamespacedPath("'+tests[i]+'") -> "'+path.toNamespacedPath(tests[i])+'"');
  console.log('path.win32.normalize("'+tests[i]+'") -> "'+path.win32.normalize(tests[i])+'"');
  console.log('path.win32.resolve("'+tests[i]+'") -> "'+path.win32.resolve(tests[i])+'"');
  try{
    var dir = fs.readdirSync(tests[i]);
    console.log('fs.readdirSync("'+tests[i]+'") success');
  } catch(e) {
    console.log(e);
    console.log('fs.readdirSync("'+tests[i]+'") failed');
  }
}

[btsimonh]

Suggest, in path.js:

  toNamespacedPath(path) {
    // Note: this will *probably* throw somewhere.
    if (typeof path !== 'string')
      return path;

    if (path.length === 0) {
      return '';
    }

    const resolvedPath = win32.resolve(path);

    if (resolvedPath.length <= 2)
      return path;

    if (resolvedPath.charCodeAt(0) === CHAR_BACKWARD_SLASH) {
      // Possible UNC root
      if (resolvedPath.charCodeAt(1) === CHAR_BACKWARD_SLASH) {
        const code = resolvedPath.charCodeAt(2);
        if (code !== CHAR_QUESTION_MARK && code !== CHAR_DOT) {
          // Matched non-long UNC root, convert the path to a long UNC path
          return `\\\\?\\UNC\\${resolvedPath.slice(2)}`;
        }
      }
    } else if (isWindowsDeviceRoot(resolvedPath.charCodeAt(0)) &&
               resolvedPath.charCodeAt(1) === CHAR_COLON &&
               resolvedPath.charCodeAt(2) === CHAR_BACKWARD_SLASH) {
      // Matched device root, convert the path to a long UNC path
      return `\\\\?\\${resolvedPath}`;
    }

    ////// Modified - since this is ONLY on windows, why not the resolved path? /////////////
    ////// is it not always our best result? /////////////
    return resolvedPath;
    ///////////////////
  },

[btsimonh]

p.s.

var tests = [
  'c:\\Windows\\System',
  'c:\\Windows/System',
  '\\\\localhost\\c$\\Windows\\System',
  '\\\\localhost\\c$\\Windows/System',
]

works fine.... so UNC paths are all good.