Imagine I have this trait that gives any model a ULID-based public_id on create:
trait HasPublicId
{
protected static function bootHasPublicId(): void
{
self::creating(function (self $model): void {
if (empty($model->public_id)) {
$model->public_id = (string) Str::ulid();
}
});
}
}
Eloquent picks up the bootHasPublicId method automatically when the trait is added to a model, which is what registers the creating hook.
The empty() check lets us pass in a specific public_id from tests or an admin tool when we need a known value.
One day the app threw a database error about a duplicate public_id.
ULID collisions seem impossible, so I shrugged it off as a one in a billion issue and moved on.
The next day it happened again. Different model, different customer. Ok, so something else is up.
I tracked it down to a "duplicate this record" action in the code somewhere:
public function duplicate(Order $order): RedirectResponse
{
$copy = $order->replicate();
$copy->save();
return redirect()->route('orders.edit', $copy);
}
replicate() copies every attribute except the primary key, timestamps, and any columns you explicitly exclude.
public_id comes along for the ride, the creating hook sees it's not empty, and the clone saves with the original's ULID, causing the collision.
The fix is a replicating hook:
self::replicating(function (self $model): void {
$model->public_id = (string) Str::ulid();
});
No empty() check here on purpose.
The whole point of replicating is to break the link with the source, so we always overwrite it.
No more collisions!
Here to help,
Aaron
P.S. A "one in a billion" bug that happens twice deserves an audience. Joel and I host our share of war stories in the community, where good debugging and bad jokes are equally welcome. Come hang out with us.
