space-before-function-paren rules for 'asyncArrow'

[SukkaW]

I have faced the issue during reviewing the PR hexojs/hexo#3954

Currently we are using ['error', 'never']:

eslint-config-hexo/eslint.js

Line 106 in ada1570

'space-before-function-paren': ['error', 'never'],

function foo() {
    // ...
}

var bar = function() {
    // ...
};

var bar = function foo() {
    // ...
};

class Foo {
    constructor() {
        // ...
    }
}

var foo = {
    bar() {
        // ...
    }
};

var foo = async() => 1

IMHO we could add a space between async & await and function for better distinguishment (['error', {"anonymous": "never", "named": "never", "asyncArrow": "always"}]), which will resulted in:

function foo() {
    // ...
}

var bar = function() {
    // ...
};

class Foo {
    constructor() {
        // ...
    }
}

var foo = {
    bar() {
        // ...
    }
};

var foo = async (a) => await a

"anonymous" and "named" retain never for consistency.

[curbengh]

All the new rules (especially ES6) inherits from airbnb style. I prefer to follow their space-before-function-paren, if that's alright.

['error', {"anonymous": "always", "named": "never", "asyncArrow": "always"}]

I don't mind either way, feel free to PR.

---

I think the reason to have a space for anonymous function is to avoid the possible confusion that function() {} is a function named function. But I don't think it matters much, I believe most (all?) of the anonymous function is already refactored to arrow function.

[curbengh]

Speaking of airbnb, I also prefer 'arrow-parens': 'error' (instead of the current 'arrow-parens': ['error', 'as-needed']). This means parenthesis is always required even when there is only one parameter. I find it easier to locate the parameter.

I previously retain 'as-needed' since hexo largely use that. But then I later found both of us actually always use parenthesis.

[SukkaW]

Currently I am using ['error', {"anonymous": "always", "named": "never", "asyncArrow": "always"}] in my own project.
But for consistency, I suggest to only add "asyncArrow": "always" at this time and we could include it in [email protected]

[curbengh]

Agree with adding asyncArrow only for now, others can defer to v5.