comma-spacing conflicts with array-bracket-spacing

[lo1tuma]

Problem description

Given the following config

{
    "env": {
        "es6": true
    },
    "ecmaFeatures": {
        "modules": true
    },
    "rules": {
        "comma-spacing": [ 2, { "before": false, "after": true } ],
        "array-bracket-spacing": [ 2, "always" ]
    }
}

and the following code:

const [ , a, ...rest ] = foo;

then the comma-spacing rule warns about an extra space before to first comma in the destructuring statement.

foo.js
  1:9  error  There should be no space before ','  comma-spacing

✖ 1 problem (1 error, 0 warnings)

when I remove the leading whitespace

const [, a, ...rest ] = foo;

then the array-bracket-spacing rule warns about a missing space after the opening bracket

foo.js
  1:7  error  A space is required after '['  array-bracket-spacing

✖ 1 problem (1 error, 0 warnings)

Same problem exist for array literals:

const foo = [ , 1, 2 ];

foo.js
  1:15  error  There should be no space before ','  comma-spacing

✖ 1 problem (1 error, 0 warnings)

I’m using ESLint version 1.1.0

---

Possible solution

I suggest that the comma-spacing rule should ignore null elements of an ArrayExpression or ArrayPattern.

[nzakas]

Not sure you really want to ignore null elements - you'd still want the extra space after, correct?

[lo1tuma]

@nzakas You are right, maybe we can just ignore the check for leading extra space of null elements?

[gyandeeps]

@lo1tuma I actually ended up filtering out the null elements in indent rule. Maybe we can have a function in ast-utils which can do that?

[lo1tuma]

@gyandeeps Not sure if we need to filter null elements completely in this case. I think we only want to make an exception for the check of leading space.