Flow enums parsing

[gkz]

Q	A
Fixed Issues?
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?	Yes (added behind optional flag)
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?	No
License	MIT

Flow is working on adding an optional (and by default off) enums feature, gated by the experimental.enums Flowconfig flag. Parsing was implemented in the Flow Parser 1.5 months ago (facebook/flow@e3ee40c).

Here, we add support for parsing Flow Enums in the Flow babel-parser plugin, also gated by an option, enums. This brings Babel's Flow parsing in line with Flow Parser's.

Here are some examples:

enum E {
  A,
  B,
}

enum E {
  A = 1,
  B = 2,
}

For more information, see this document: https://github.com/gkz/enums

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/11410/

[buildsize]

File name	Previous Size	New Size	Change
babel-preset-env.js	2.36 MB	2.39 MB	27.7 KB (1%)
babel-preset-env.min.js	1.35 MB	1.36 MB	13.47 KB (1%)
babel.js	2.91 MB	2.94 MB	27.88 KB (1%)
babel.min.js	1.61 MB	1.62 MB	13.58 KB (1%)

[nicolo-ribaudo]

Can enums be exported? Is this valid?

export default enum {}

[existentialism]

/cc: @babel/flow

[gkz]

Thank you for reviewing @nicolo-ribaudo! I will update/respond this week

[gkz]

Will add support for parsing export of enums

[gkz]

I have updated the pull request as per comments

[gkz]

Not sure exactly the purpose of the "request a review" button on GitHub, but I clicked it. Actually looking at this it doesn't look like PRs need to be "approved" before they are merged, so feel free to ignore the request (if you have no additional comments)

[nicolo-ribaudo]

We need to ✔️ to merge a PR (and I won't merge it until the 7.7.0 release anyway)