update to ESLint 3+ rule format

[benmosher]

http://eslint.org/blog/2016/07/eslint-new-rule-format (see part about the auto-transform tool)

@ljharb made an interesting point on the PR for the React plugin about maybe not being too aggressive/hasty about this.

I'm planning to do this as part of the semver-major bump to 2.x for this plugin, ~~though there is nothing else to really gain from being 3.x+ only with ESLint, other than that I want to drop support for Node 0.10 and 0.12. ~~

But it's not obvious to me why anyone would want to stay on ESLint 2 if they are using Node 4+, either.

~~So it feels like a major release would be the right time to bump to support ESLint 3. ~~

Feedback (especially arguments against this) desired/welcome.

edit: thanks to @jfmengels about digging in on this. turns out new format is supported in v2

[ljharb]

My preference would be to retain both eslint 2 + 3 compat, as well as node 0.10 compat - ideally, at least one version exists for the entire setup such that those who have not yet upgraded (and there are many valid reasons why someone may not have) can still have a smooth path to upgrading - ie, they can upgrade their linting deps, and then, separately, upgrade node - and then, separately, upgrade their linting deps again to the one that's functionally equivalent but drops old node/eslint.

[benmosher]

related: a55cd67#commitcomment-18156683

[jfmengels]

Correct me if I'm wrong, but I get the feeling that both ESLint 2 and ESLint 3 are compatible with both rule formats.

[ljharb]

If that's true then of course we should change it, but I can't conceive of how a brand new format would be supported by an old version.

[benmosher]

Docs don't confirm or deny that, AFAICT. Just that both formats are supported in 3.x.

Have you tested? It's not obvious to me how (or why) that would work.

[jfmengels]

https://gitter.im/eslint/eslint?at=577e7ebce483756e106004ad

https://gitter.im/eslint/eslint?at=577e82e359cfbd4c5e3e8378

cc @sindresorhus @jamestalmage @novemberborn in case you're interested

Meaning the only breaking change when moving to ESLint 3 is the use for Node v4+ ES6 features, not the rule format.

[ljharb]

I'm surprised the blog post about it was coupled with the v3 release, but that's great news. Upgrade away!

[benmosher]

fixed in 20079c6, will deploy via v2 anyway