react-in-jsx-scope does not understand fragments

[dantman]

If you use <></> fragment syntax the react-in-jsx-scope rule will not declare React as in scope and the no-unused-vars will fail on the React import.

However React is required for fragment syntax as well as normal element syntax.

import React from 'react';

export default () => <>fragment</>;

[dantman]

The fix for this appears to be extremely simple. react-in-jsx-scope.js just needs to apply itself to JSXOpeningFragment in addition to JSXOpeningElement.

[ljharb]

@dantman that sounds great! However, we'll also want to make sure this change only applies after whichever React version added fragment support.

[bumpah]

seems like 16.2.0 -version introduced improved support for fragments.
https://reactjs.org/blog/2017/11/28/react-v16.2.0-fragment-support.html