Parentheses for arrow function aruments

[fanatid]

Probably this question was already raised, sorry if this issue is duplicate.

Right now all this expression are valid:

const fn1 = () => {}
const fn2 = (a) => {}
const fn3 = a => {}
const fn4 = (a, b) => {}

When we have exactly one argument, parentheses can be or not be. Will some of this expression standardize in standard? Or two expression will be always valid?

[feross]

This is a tough one. We tried enforcing "always use parens around arrow function arguments" but had to revert it since omitting parens is quite a popular style.

This was discussed in #309, #414, and standard/eslint-config-standard#63 if you want to dig into the historical discussion.

[feross]

Feel free to continue discussing here, but I'm closing this since I don't expect we'll make any changes anytime soon around this rule.