Update eslint-plugin-react and enable new rules

[fson]

Some new rules had been added that are a good fit for this project. All of these are either already runtime warnings in React (no-danger-with-children, style-prop-object) or React features that are going to be deprecated in the future (no-find-dom-node). The new rules:

• react/no-danger-with-children (Rule proposal: prevent both children and dangerouslySetInnerHTML at the same time jsx-eslint/eslint-plugin-react#710)
• react/no-find-dom-node (Rule proposal: warn against using findDOMNode() jsx-eslint/eslint-plugin-react#678)
• react/style-prop-object (Rule proposal: ensure style prop on DOM element tags is an object jsx-eslint/eslint-plugin-react#715)

[fson]

I also considered the new no-unused-prop-types rule, but wasn't sure if it would be a good fit here. Any thoughts on it @gaearon?

[gaearon]

I think no-find-dom-node is a bit too early for this kit right now. It's okay for more mature setups but I'm worried beginners will copy and paste examples from StackOveflow and be confused by this warning.

I'm open to adding it in a year or so.

[fson]

Alright, I removed no-find-dom-node. I think to be included in a beginner friendly configuration like CRA, the error message would also need to be better than the current Do not use findDOMNode, at least explain that you should use refs instead and possibly link to docs.

[gaearon]

Exactly. (I'd appreciate if somebody did that.)

[gaearon]

Is Travis acting up?

[fson]

npm ERR! peerinvalid The package eslint-plugin-react@6.3.0 does not satisfy its siblings' peerDependencies requirements!
npm ERR! peerinvalid Peer eslint-config-react-app@0.1.0 wants eslint-plugin-react@5.2.2

Uh, it installs eslint-config-react-app@0.1.0 from npm that still has the old eslint-plugin-react@5.2.2 as a peer dependency. I guess we shouldn't change the ESLint plugin versions in react-scripts until we publish eslint-config-react-app with the new version? But then it fails when installing locally, because our local config depends on the new version... Tricky 😅

[gaearon]

e2e script should use current versions of all packages, not ones from npm. Can we make it do that? Maybe need to run lerna bootstrap or whatever?

[gaearon]

I’m going to trust that this works but we need to figure out the e2e fix for this.

[gaearon]

#698