New rule: disallow nested es6 destructuring

The rule should warn in these scenarios:

let {a: {b}, c} = obj;    // 1
let {a, a: {b}, c} = obj; // 2
let [a, {b}] = arr;       // 3
let [[a]] = arr;          // 4

The rule should NOT warn in these scenarios:

let {c} = obj; let {b} = obj.a; // refactored 1
let {a, c} = obj; let {b} = a;  // refactored 2
let {a, b, c} = obj;
let [a, b, c] = arr;

This rule is stylistic. Destructuring of nested objects can be confusing and is usually better written in several smaller steps.

I think it’s generic enough for core.

I’m thinking also about configuration options to ignore array destructuring (then examples 3 and 4 would be valid).

I don’t think I can implement it anytime near, but if I need it urgently somewhere, I will do 😃

[nzakas]

@ianvs the issue here is whether or not it belongs in core, not necessarily if the rule is useful. Remember, we purposely raised the bar for the core because we already have over 200 rules.

And a reminder for everyone: our job is not to determine if a rule is useful, it’s to determine if it’s so important that ESLint would seem incomplete without it. Our guidelines: http://eslint.org/docs/developer-guide/contributing/new-rules

[IanVS]

👍 Personally I’ve spent way too much time trying to decipher nested destructurings, and would love to see a rule like this. Whether it’s in core, or a plugin is up for debate, but I think it would be a great rule regardless.