ESLint v4 and arrow functions as properties

[oandregal]

On upgrading ESLint to v4, we ran into the following issue: class properties that are arrow functions are reported as no-undef issues.

So this is no longer valid:

class MyClass extends Component {
	myArrowFunction = () => ...;
}

But this is:

class MyClass extends Component {
	myFunction() {...}
}

This feature is provided by the transform-class-properties transformation, included in the stage2 babel preset. There are other projects that are reporting the same. This seems somehow related to ESLint v4, as in the v3 line this error doesn't happen.

Will need more time to investigate, so in the meantime, I'm reverting the upgrade.

[oandregal]

babel-eslint, the parser we use for ESLint, doesn't support ESLint v4 yet. This issue has been reported.

[oandregal]

Addressed by #24308