Underscore prefixed config (_auth) provided by env var is converted to dash (-auth)

[krmcbride]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
npm config that have a _ prefix (_auth, _authToken, _password), when provided as environment variables (export npm_config__auth=blah) have their _ prefix converted to - (-auth instead of _auth for example).

If the current behavior is a bug, please provide the steps to reproduce.

npm_config__auth=abc yarn config get _auth
undefined

npm_config__auth=abc yarn config list | grep abc
  '-auth': 'abc' }

What is the expected behavior?
The npm config which start with _ have their prefix untouched (npm_config__auth -> _auth)

Please mention your node.js, yarn and operating system version.
yarn 1.1.0 and 1.2.0
node 6.11.4
debian jessie

[NicholasBoll]

I found the line that is doing this:

yarn/src/registries/base-registry.js

Line 174 in 723fc3e

key = key.replace(/_/g, '-');