Run prepareNestedBatches on append/prependToChain & chain

[SabatinoMasala]

The issue with appending/prepending a batch from within a job

Currently, when appending or prepending a batch from within a job, you get the following error:

Serialization of 'Closure' is not allowed 

Diving into the Queuable class, this is because prepend/appendToChain fails to turn the PendingBatch into a ChainedBatch. The workaround for this is by creating a ChainedBatch manually as described here:
#52468

Proposal

Run ChainedBatch::prepareNestedBatches when appending or prepending a job from within another job, so you can add a batch onto a current chain as follows:

<?php

namespace App\Jobs;

use Illuminate\Bus\ChainedBatch;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Foundation\Bus\Dispatchable;
use Illuminate\Foundation\Queue\Queueable;
use Illuminate\Queue\InteractsWithQueue;
use Illuminate\Queue\SerializesModels;
use Illuminate\Support\Facades\Bus;

class Chainer implements ShouldQueue
{
    use Queueable;

    public function __construct() {}

    public function handle(): void {
        $batch = Bus::batch([
            new Logger('From batch'),
            new Logger('From batch'),
            new Logger('From batch'),
            Bus::batch([
                new Logger('From nested batch'),
            ]),
            new Logger('From batch'),
        ]);
        $this->appendToChain($batch);
    }
}

Discussion

Currently, my implementation of appendToChain/prependToChain wraps the single job in a collection to match the expected format of ChainedBatch::prepareNestedBatches() - this feels kinda unnecessary, so this could be further improved by either:

• allowing an array of jobs to be appended/prepended
• refactoring prepareNestedBatches and creating a method that accepts a single job (in addition to the currently available method that accepts a collection)

Happy to make the necessary changes if needed.

[SabatinoMasala]

I've also just updated the chain method for consistency.

e6a3735

[taylorotwell]

Thanks!