A cleaner fix for the duplicate ULID problem

In a previous tip, I walked through a duplicate public_id bug caused by Eloquent::replicate() carrying the ULID over to the clone.

The fix I landed on was a replicating hook that overwrites public_id on the new instance.

That works, but while digging in the framework source I noticed Eloquent\Model::replicate() already spreads ...$this->uniqueIds() into its list of excluded attributes.

So instead of using a replicating hook, we can just tell Eloquent that public_id is a unique id and shouldn’t come along for the ride:

trait HasPublicId
{
  protected static function bootHasPublicId(): void
  {
    self::creating(function (self $model): void {
      if (empty($model->public_id)) {
        $model->public_id = (string) Str::ulid();
      }
    });
  }

  public function uniqueIds(): array
  {
    return ['public_id'];
  }
}

Now replicate() strips public_id from the new instance, the creating hook sees an empty value on save, and a fresh ULID gets generated.

One hook, no asymmetry to explain.