Configuration doesn't inherit with extends keyword

[IgorNovozhilov]

• Version: 7.8.0
• Platform: linux mint

This change has broken configuration inheritance:
99436ef#diff-40d93e4e5f4b94fc8a34a87a3328651c24e855051bfcdd6944dee76f9c82b8d4L116

see: http://yargs.js.org/docs/#api-reference-configobject-extends-keyword

custom configParser doesn't provide inheritance
99436ef#diff-40d93e4e5f4b94fc8a34a87a3328651c24e855051bfcdd6944dee76f9c82b8d4R15

[calebcartwright]

@bcoe know you're very busy but would be great to get your perspective on some paths to potentially resolve this issue. Fundamentally I think there's some change/guidance needed on how extends is managed and/or exposed between yargs and yargs-parser, as I've seen this same type of challenge pop up elsewhere (e.g. mocha) with extends not working at all or only partially working.

Realize the yargs discussion would be better placed elsewhere, but mentioning here since that seems like the right place to address as opposed to trying to find a solution that works around/with the issue in c8 and other tools (however if there is a viable workaround that'll get this feature working in c8 then i'd be happy to attempt a PR)

[bcoe]

@calebcartwright yargs exposes an applyExtends helper, which can be used to configure the extension behavior.

Does this look like it would do the trick? #343

[calebcartwright]

Awesome thank you, that seems to do it! I didn't realize applyExtends had become public (though it's admittedly been a while since i checked on the similar mocha issue).