async (t) => { } - Expected parentheses around arrow function argument.

[azhang]

I'm getting Expected parentheses around arrow function argument. errors with my async arrow functions. Perhaps this is more of a eslint issue than a standardjs issue?

[feross]

There's already another discussion about this here: #414

[azhang]

Oh, actually I don't get that issue. I only get errors on async arrow functions.

(t) => {} works
async (t) => {} errors

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On Feb 10, 2016, at 1:43 PM, Feross Aboukhadijeh notifications@github.com wrote:

Closed #416.

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[feross]

Oh didn't realize this was only for async arrow functions.

[dhax]

having the same issue with async arrow function with basic setup:

   "standard": {
    "parser": "babel-eslint"
  },
  "devDependencies": {
    "babel-eslint": "^4.1.8",
    "babel-preset-es2015-node5": "^1.1.2",
    "babel-preset-stage-0": "^6.3.13",
    "babel-register": "^6.4.3",
    "standard": "^6.0.4"
  }

[cesarandreu]

Having the same issue. This prevents us from upgrading to standard v6.

[azhang]

I made an issue in the babel-eslint repo as well: babel/babel-eslint#252

[benjyhirsch]

This is a known issue with some of the rules in babel-eslint, hence https://github.com/babel/eslint-plugin-babel

From the description:

An eslint plugin companion to babel-eslint. babel-eslint does a great job at adapting eslint for use with Babel, but it can't change the built in rules to support experimental features. eslint-plugin-babel re-implements problematic rules so they do not give false positives or negatives.

One of the rules is:

babel/arrow-parens: Handles async functions correctly

[cesarandreu]

This issue keeps us from upgrading, we're using async arrow functions a lot. Even if we add eslint-plugin-babel, according to #404 it seems v7 is gonna be removing "rules", so we'd have no way of replacing the eslint rule with the plugin rule?

Hmm, maybe making a standard-babel would make sense?

[feross]

@cesarandreu That's certainly one option, but I wonder if we shouldn't just disable/change this rule given the opposition to it in the other issue #414 (comment)

[cesarandreu]

That'd also work :D. I've kinda grown to like it, just because it's consistent, but since it breaks with async arrow functions it's annoying :(.

[namuol]

TL;DR -- Here's the workaround that solves the problem:

npm install eslint-plugin-babel --save-dev

Then, in your eslintrc:

{
  // ...

  "plugins": [
    "babel"
  ],

  "rules": {
    // ...
    "arrow-parens": 0,
    "babel/arrow-parens": 2
  }
}

[feross]

This should be fixed now in standard version 7.0.0-beta.0 which removed the arrow function parens rule.