How to persist modified order of cart line items?

Question

I wrote a function to sort / re-order the line items in a cart.

function sortCart(Order $order) {
    $lineItems = $order->getLineItems();
    $lineItemsOrdered = array();

    // [...]

    $order->setLineItems($lineItemsOrdered);
}

it works, but obviously this only changes the in-memory order object. how can I make it so that the order is also persisted in the database? I would like to see the line items in the modified order in the craft backend.

---

edit:

the sorting logic depends on a field set in the EVENT_AFTER_CAPTURE_PRODUCT_SNAPSHOT event, so EVENT_BEFORE_SAVE won't work because it runs earlier.

Craft::$app->getElements()->saveElement($order, false); in an adjuster will cause an endless loop.

how do I do this?

---

edit: apparently the order is determined by the creation date of the line items. however this doesn't work either:

Event::on(
    Order::class,
    Order::EVENT_BEFORE_SAVE,
    function (ModelEvent $event) {
        $order = $event->sender;
        sortCart($order); // also sets `dateCreated` on line item

        // log shows the correct order/timestamps
        foreach ($order->getLineItems() as $item) {
            Module::info($item->dateCreated->format(\DateTime::ATOM) . ': ' . $item->getDescription());
        }
    }
);

Answer 1

Can you try using EVENT_POPULATE_LINE_ITEM? Not sure, but it fired AFTER the product & variant snapshot event. Here you can take any necessary fields & data, including one from the snapshot.

    use yii\base\Event;
    use craft\commerce\events\LineItemEvent;
    use craft\commerce\services\LineItems;

    ...

    Event::on(
        LineItems::class,
        LineItems::EVENT_POPULATE_LINE_ITEM,
        function (LineItemEvent $e) {
            $lineItem = $e->lineItem;
            $snapshot = $lineItem->snapshot;
            $order = $lineItem->order;
            // ....

            // Changing some values
            $lineItem->privateNote = 'Testing';
        }
    );