Add a --fix option for no-extra-parens

[not-an-aardvark]

I'm using Node v6.4.0 and ESLint v3.3.1.

I think it would be useful to have an autofix option for the no-extra-parens rule. I think the fixer would be fairly simple; it would just remove the offending parens from the source code.

Presumably, the fixer would follow the same options as the rule itself to determine whether parentheses are gratuitous. For example:

/* eslint no-extra-parens: "error" */

var foo = (bar && baz) || qux;

// gets fixed to:

var foo = bar && baz || qux;

/* eslint no-extra-parens: ["error", "all", { "nestedBinaryExpressions": false }] */

// does not get fixed, because these parens are not errors with nestedBinaryExpressions: false
var foo = (bar && baz) || qux;

---

One special case for no-extra-parens is when a parenthesized expression is immediately preceded by a keyword:

//  In this case, the fixer should insert a space in addition to removing the parens:
function foo () {
  return(0);
}

// gets fixed to:

function foo () {
  return 0;
}


// However, the fixer probably should not insert a space if a space is already present:
function foo () {
  return (0);
}

// gets fixed to:

function foo () {
  return 0;
}

---

If this issue gets accepted, I would be happy to send a PR for it.

edit: Added a special case that I noticed

[platinumazure]

Sounds reasonable to me. I'll endorse this (:+1:).

[mysticatea]

👍

[gyandeeps]

👍

[ilyavolodin]

👍 I'll champion this.