refactor: Move JS parsing logic into JS language

[nzakas]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[x] Add something to the core
[ ] Other, please explain:

What changes did you make? (Give an overview)

This PR moves JS parsing and config handling logic into a new JS language object (/lib/languages/js/index.js), and includes:

• Creation of the VFile class (implements the File interface from the RFC) and tests.
• Creation of the JS language object (implements the Language interface). This deviates slightly from the RFC in that I've renamed "options" in all places to "languageOptions" to avoid confusion. Otherwise, I was constantly assigning back and forth between these two names.
• Added language: "@/js" to the default config.
• Moved languageOptions validation out of the default schema and into the JS language object.
• Updated flat config array tests to verify all the relocated behavior works.
• Created a generic languageOptionsSchema that does not validate the keys (that is now done in the JS language object) but preserves the merge behavior.

Refs #16999

Is there anything you'd like reviewers to focus on?

I think these changes are backwards-compatible, but would like another set of eyes.

languageOptionsSchema is the part I'm most concerned about. The previous merging behavior was very JS-specific, so I tried to come up with a generic version that would make sense for other languages. Please double-check that.

[netlify]

✅ Deploy Preview for docs-eslint canceled.

Name	Link
🔨 Latest commit	ff2233c
🔍 Latest deploy log	https://app.netlify.com/sites/docs-eslint/deploys/6656125e0f64380008253c46

[mdjermanovic]

Sorry for the delay, I plan to review this this week.

[aladdin-add]

to confirm: DEFAULT_ECMA_VERSION set to 5, for eslintrc-compat?

[nzakas]

That's correct. The eslintrc branch of logic will still use this file, so want to cover our bases.

[mdjermanovic]

This might be a breaking change because this code was executed for non-estree ASTs.

[nzakas]

Interesting. Without this, several tests failed, so I thought we were skipping logic. I'll take another look.

[mdjermanovic]

@christian-bromann looks like there's a problem in WebdriverIO:

[0-0] RUNNING in chrome - file:///tests/lib/linter/linter.js
[0-0]  Error:  Test failed due to following error(s):
  - downloadFile.js?v=74a71965: Uncaught SyntaxError: The requested module '/node_modules/jszip/dist/jszip.min.js?v=74a71965' does not provide an export named 'default'

[christian-bromann]

@mdjermanovic I will take a look tomorrow.

[christian-bromann]

@mdjermanovic please re-run the tests, it should pass now.

[mdjermanovic]

@christian-bromann now the test fails with:

Execution of 1 workers started at 2024-05-28T06:17:14.648Z

[0-0] RUNNING in chrome - file:///tests/lib/linter/linter.js
[0-0]  Error:  Test failed due to following error(s):
  - linter.js: Timed out after 300s waiting for test results

[0-0] FAILED in chrome - file:///tests/lib/linter/linter.js

 "concise" Reporter:
========= Your concise report ==========
chrome-headless-shell (v125.0.6422.60) on linux
❌ Failed to setup tests, no tests found


Spec Files:	 0 passed, 1 failed, 1 total (100% completed) in 00:05:03 

[christian-bromann]

@mdjermanovic all test started to run extremely slow, I will investigate as to why.