Context: How does an order saving work?
958164/app/code/Magento/Payment/Observer/SalesOrderBeforeSaveObserver.php#L13-L43
/**
* Set forced canCreditmemo flag
*
* @param \Magento\Framework\Event\Observer $observer
* @return $this
*/
public function execute(\Magento\Framework\Event\Observer $observer)
{
/** @var \Magento\Sales\Model\Order $order */
$order = $observer->getEvent()->getOrder();
if ($order->getPayment()->getMethodInstance()->getCode() != 'free') {
return $this;
}
if ($order->canUnhold()) {
return $this;
}
if ($order->isCanceled() || $order->getState() == \Magento\Sales\Model\Order::STATE_CLOSED) {
return $this;
}
/**
* Allow forced creditmemo just in case if it wasn't defined before
*/
if (!$order->hasForcedCanCreditmemo()) {
$order->setForcedCanCreditmemo(true);
}
return $this;
}