[12.x] Let Collection collect() method accept key to collect

[ralphjsmit]

Sometimes it can be very handy when working with collections if you could select a key and get another collection of that key. This PR allows the ->collect() to accept a key on Collections.

$collection = collect([
   'foos' => ['foo', 'bar', 'baz'],
   'other-keys' => 'foo',
]);

$foos = $collection->collect('foos');
// Collection [foo/bar/baz]

Thanks!

PS: I am not sure if this is considered a breaking change because of the change in the Enumerable contract, or if this contract is only supposed for internal use.

[rodrigopedra]

What happens in this case?

$collection = collect([
   'foos' => ['foo', 'bar', 'baz'],
   'other-keys' => 'foo',
   'user' => User::find(1),
]);

$foos = $collection->collect('user');
// ???

As the user key only has an Illuminate\Contracts\Support\Arrayable element, is the result something like this?

new Collection([User::find(1)])

Or something like this?

new Collection(User::find(1)->toArray())
// == new Collection(['name' => ..., 'email => ..., ...])

An option to work around this case would be:

return new Collection($key ? Arr::wrap($this->get($key)) : $this->all());

---

Regarding this:

I am not sure if this is considered a breaking change because of the change in the Enumerable contract, or if this contract is only supposed for internal use.

All classes, interfaces, methods and properties meant only for internal use, are marked with an @internal tag on their docblock.

So it is a breaking change, as it changes both an interface, and a class' public method signature, and should be sent to the master branch.