feat: add MOCHA_OPTIONS env variable

[icholy]

Description of the Change

The MOCHA_OPTIONS environment variable is a space-separated list of command-line options. It essentially copies node's approach with NODE_OPTIONS

The config priority is:

1. Command-line args
2. MOCHA_OPTIONS environment variable.
3. RC file (.mocharc.c?js, .mocharc.ya?ml, mocharc.json)
4. mocha prop of package.json
5. default configuration (lib/mocharc.json)

Alternate Designs

Yargs has support for env variables: https://yargs.js.org/docs/#api-reference-envprefix
However, using this feature would result in a separate env variable for each option:

Ex:

• MOCHA_BAIL
• MOCHA_ALLOW_UNCAUGHT
• MOCHA_FAIL_ZERO
• etc ...

I decided to to go with MOCHA_OPTIONS because it seems less intrusive and that's how node does it too.

Why should this be in core?

I don't see how it could live anywhere else.

Benefits

My specific use-case is specifying MOCHA_OPTIONS='--inspect-brk' when calling npm run test from vim.

Possible Drawbacks

• More code is always a liability.
• More config sources can make things more difficult to debug.

Applicable issues

Fixes #4330.

[icholy]

@juergba have you had a chance to look this over?

[github-actions]

This PR hasn't had any recent activity, and I'm labeling it stale. Remove the label or comment or this PR will be closed in 14 days. Thanks for contributing to Mocha!

[github-actions]

This PR hasn't had any recent activity, and I'm labeling it stale. Remove the label or comment or this PR will be closed in 14 days. Thanks for contributing to Mocha!

[icholy]

@outsideris I still need this feature. Would I be able to get some feedback?

[JoshuaKGoldberg]

👋 coming back to this @icholy, are you still interested in working on this PR? As of #5027 there are maintainers who can review it now. No worries if you no longer have time - but if you do that'd be great!

[icholy]

Yes!

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: icholy / name: Ilia Choly (d986a9a, a2868fe)
• ✅ login: voxpelli / name: Pelle Wessman (4b87ce6)

[JoshuaKGoldberg]

Yay! We're not quite ready to start reviewing PRs yet, but hope to soon.

Note that I don't see any linked issues. The contributing guidelines right now ask for that so that folks can discuss the change first. We'll continue to require that after #5038. Was there any impetus for this PR besides what's in the description?

[coveralls]

coverage: 94.359% (+0.001%) from 94.358%
when pulling 4b87ce6 on icholy:master
into 472a8be on mochajs:master.

[icholy]

There's no separate issue, the PR description contains all the context I have. I can create an issue if you'd like though.

[JoshuaKGoldberg]

That would be lovely, yes please!

Note that the three of us new maintainers are still ramping up on the project, so it might be some weeks (or even months 😞) before we have enough context to really triage the issue and review this PR. We'll do our best to get to it soon though!

[icholy]

That's alright. It's been two years, what's another month or two?

[JoshuaKGoldberg]

Sweet! Really pleasing to see such a clean implementation. And with thorough tests! 👏

Just requesting changes on docs.