normalized-tmpdir

Normalize the value returned from os.tmpdir() to eliminate OS-specific symlinks and naming variations. This is mainly useful in tests that rely on path comparisons.

Currently-handled issues

Mac

os.tmpdir() may return /var/... which is a symlink to /private/var/.... This can be fixed with fs.realpathSync().

Windows

On Windows, os.tmpdir() uses the value of the TEMP or TMP environment variables. In some cases (including on GitHub Actions runners), if the user directory name is more than 8 characters, these variables may include a short (8.3) name for the user directory.

Node doesn't have an API to convert between short and long names. There are various possible workarounds, including:

• Use powershell: this is an official API but much more expensive.
• There's no cmd built-in or one-liner for this. However, attrib.exe appears to always expand the last path segment into a long path.
• If the only short segment is the user directory name, replace it with the path from os.homedir() (as long as it's the same directory and not a short name).

This package currently tries the os.homedir() workaround first (since it doesn't require spawning a process), and tries iterating through path segments and calling attrib.exe as a fallback.

API

normalizedTmpdir(options?): string

Return a normalized version of os.tmpdir().

import { normalizedTmpdir } from 'normalized-tmpdir';

const tmpdir = normalizedTmpdir();

The function accepts an options object:

• console?: boolean | { warn: typeof console['warn'] }: By default, the library does not log warnings if normalization fails. If this option is true, log warnings to the default console. If a console object is provided, use it for logging.

To avoid potentially doing the Windows normalization on every call, the calculated full path is cached.

Example: Using with Jest console mocks

If you have Jest tests that mock the console methods, but you want errors from normalizedTmpdir to display anyway (for easier debugging), you can do the following:

import { normalizedTmpdir } from 'normalized-tmpdir';
import realConsole from 'console';

const tmpdir = normalizedTmpdir({ console: realConsole });

expandShortPath(shortPath: string): string | false

On Windows only: expand an absolute path with short (8.3) segments to a long path. If the user name is the only short segment, and shortPath is under os.homedir() (which must not include any short segments), uses os.homedir() as a replacement for the short part. Otherwise, expands each short segment of the path using attrib.exe.

Returns the expanded path, or false if not on Windows, it's an unsupported type of path, or there's an error expanding any of the segments.

import os from 'os';
import { expandShortPath } from 'normalized-tmpdir';

if (os.platform() === 'win32') {
  // Example: expand a short path to C:\Users\VeryLongName
  const longPath = expandShortPath('C:\\Users\\VERYLO~1');
}