no-useless-spread: Check more cases

[fisker]

(The badge links to a different issue but the bounty applies to this issue)

Fail

const array = [
	...foo.map(/* ... */)
];

Other array methods returns a new array, eg: concat(), flatMap(), copyWithin(), etc
Other known arrays, eg: Array.from(), Object.keys(), ...

Pass

const array = foo.map(/* ... */);

These cases are like "useless array copy"

[rightaway]

It can check that spread isn't used when there's only a single property. So { ...expression } and [ ...expression ] should both just be expression.

[fisker]

It can check that spread isn't used when there's only a single property.

It can be making a shallow copy. In object spread, it can also ensuring object type.

function foo(options) {
	const {bar} = {...options};
}

[rightaway]

Could checking this be added as an option? Sometimes spread is used just to combine things, so if you start off with { ...a, b: null, c: null } and then later remove b and c you're left with { ...a } when you really could replace it with a.

If there was this option you could disable the rule in cases when you want a shallow object.

[fisker]

@rightaway
I'm going to skip check spreading single UNKNOWN object, if you still want it please open a separate issue.