[5.3] Return early when chunk size is less than zero

[jstoone]

I found that this PR might be relevant after working on spatie/laravel-collection-macros#13, and figured it might be relevant for the core. It is very much an edge-case.

The problem

Many use chunk() as a way to split their collection into parts, so that it's easier to create columns of content. But if the $size is dynamically calculated, it may occur that the result of the calculation is 0.
If array_chunk() is given a value less than 1, it will throw an error. This will, from my point of view, generate a lot of unnecessary empty checks in peoples views.

The solution

If the chunk() method would return early if the given chunk size was == 0,

[GrahamCampbell]

You should return a new instance, not the same one please.

[jstoone]

It now returns a new instance instead.

[taylorotwell]

Honestly to me it should throw an error? If you're passing 0 into chunk it definitely shouldn't return the current collection. That doesn't make any sense to me. If anything it should return an empty new collection as Graham said.

[jstoone]

I totally see your point(s).

In either case I think it would be nice to see it handled in another way. It's not always directly obvious when getting an exception/error from array_chunk.

I'll change the comments mentioned in the review by @GrahamCampbell. If you feel like throwing an error @taylorotwell, I think it would be more appropriate to message that the error is from within Collection::chunk.

I hope that makes sense.

[GrahamCampbell]

We should throw an invalid argument exception for less than 0 also.

[jstoone]

This has now been added, together with a test.

[vlakoff]

Maybe a similar change could be applied to Query\Builder and Eloquent\Builder's chunk and chunkById methods.