Rule Proposal: no-empty-pattern [$10]

[mysticatea]

Spawned from #3658.

The following code does not raise an syntax error.

let {a: {}} = foo;

But it's considered developer's intent is below.
Because an empty ObjectPattern effects nothing.

let {a = {}} = foo;

So this proposal defines new no-empty-pattern rule.
This rule considers the following patterns as warnings:

let {} = foo;
let [] = foo;
let {a: {}} = foo;
let {a: []} = foo;
function foo({}) {}
function foo([]) {}
function foo({a: {}}) {}
function foo({a: []}) {}

This rule does not consider the following patterns as warnings:

let {a = {}} = foo;
let {a = []} = foo;
function foo({a = {}}) {}
function foo({a = []}) {}

---

I'm not sure this rule name is good.

Did you help close this issue? Go claim the $10 bounty on Bountysource.

[mysticatea]

import {} from "foo"; is the similar one.

[mysticatea]

Is no-empty-declaration a good name?
These patterns does not declare any variable.

EDIT: I had forgotten let {a, b: {}} = foo;

[ilyavolodin]

What about var and const? I assume those are going to be affected too?

[mysticatea]

Yes, this rule covers var and const.

I thought this rule is super simple.

return {
    "ObjectPattern": function(node) {
        if (node.properties.length === 0) {
            context.report(node, "Unexpected empty object pattern.");
        }
    },
    "ArrayPattern": function(node) {
        if (node.elements.length === 0) {
            context.report(node, "Unexpected empty array pattern.");
        }
    }
};

[nzakas]

Yeah, seems like a good idea

[alberto]

@mysticatea are you working on this?

[mysticatea]

@alberto No yet. I am happy if you work on this :)

[alberto]

Thanks, I'll give it a try. :)

[nzakas]

@alberto there's a bounty on this issue that you can claim: https://www.bountysource.com/issues/26471568-rule-proposal-no-empty-pattern?utm_campaign=plugin&utm_content=tracker%2F282608&utm_medium=issues&utm_source=github

[alberto]

That should go to @mysticatea, it was all his code. :)

[nzakas]

Okay, @mysticatea there's money for you!