Common/Listener/OrderNotifyListener.php
protected function watch(OrderInterface $order)
    {
        // Abort if notify disabled or sample order
        if (!$order->isAutoNotify() || $order->isSample()) {
            return;
        }

        // Abort if sale has notification of type 'SALE_ACCEPTED'
        if ($order->hasNotifications(NotificationTypes::ORDER_ACCEPTED)) {
            return;
        }

        // Abort if state has not changed for 'ACCEPTED'
        if (!$this->didStateChangeTo($order, OrderStates::STATE_ACCEPTED)) {
            return;
        }

        $this->notify(NotificationTypes::ORDER_ACCEPTED, $order);
    }
protected function watch(OrderInterface $order)
    {
        // Abort if notify disabled or sample order
        if (!$order->isAutoNotify() || $order->isSample()) {
            return;
        }

        // Abort if sale has notification of type 'SALE_ACCEPTED'
        if ($order->hasNotifications(NotificationTypes::ORDER_ACCEPTED)) {
            return;
        }

        // Abort if state has not changed for 'ACCEPTED'
        if (!$this->didStateChangeTo($order, OrderStates::STATE_ACCEPTED)) {
            return;
        }

        $this->notify(NotificationTypes::ORDER_ACCEPTED, $order);
    }
Order watcher.

@param OrderInterface $order