[Commerce 5] Purchasing a variant that has 0 stock or setting unlimited stock on variant

[hatyi]

Hello all

I have a requirement from a client that says if "some conditions are fulfilled users should be able to buy a purchasable even if it doesn't have stock".
Could you be so kind to help me on how I can solve this in Commerce 5?
Or just point me to some kind of documentation or direction where I can get this information myself.

Alternative solution could be to set unlimitedStock on all variants (but I have no idea how to do this since the documentation doesn't cover it, just mentions it), naturally this would mean I have to throw out all these new mechanics around inventory management that had been introduced in the latest version. Client doesn't have multiple warehouses so it won't be an issue.

Thanks a lot in advance.

[hatyi]

Based on the help I got from @AugustMiller I think I was able to make some progress with this.
Of course I need to do some testing to verify, but so far I think something like this might work.

Event::on(
    Purchasables::class,
    Purchasables::EVENT_PURCHASABLE_AVAILABLE,
    function (PurchasableAvailableEvent $event) {
        /** @var User $currentUser */
        $currentUser = $event->currentUser;
        /** @var Order $order */
        $order = $event->order;
        $purchasable = $event->purchasable;
        
        $myCustomBusinessLogicResult = true; //TODO
        // rest of the validations were copied over from:
        // https://github.com/craftcms/commerce/blob/5.x/src/elements/Variant.php#L356-L371
        // https://github.com/craftcms/commerce/blob/5.x/src/base/Purchasable.php#L398-L426
        // except for stock
        
        if( 
            $myCustomBusinessLogicResult 
            && $event->purchasable->availableForPurchase 
            && $event->purchasable->getStatus() === Element::STATUS_ENABLED
            && !PurchasableHelper::isTempSku($event->purchasable->getSku())
            && !$event->purchasable->getPrimaryOwner()->getIsDraft()
            && $event->purchasable->getPrimaryOwner()->status === Product::STATUS_LIVE
        ) {
            // Force Craft to think this variant is available for purchase
            $event->isAvailable = true;
            
            // Check if we have enough stock
            if( $order ) {
                foreach ($order->getLineItems() as $lineItem) {
                    if( $lineItem->purchasable->id === $event->purchasable->id && $lineItem->qty > $lineItem->purchasable->stock ) {
                        // Increase stock based on the desired amount through custom behavior
                        $lineItem->purchasable->updateStock($lineItem->qty);
                    }
                }
            }
        }
    }
);

And I have added the updateStock method as a behavior on the variants based on what I have found in \craft\commerce\controllers\InventoryController::actionEditLocationLevels

public function updateStock(int $qty) : bool {
    try {
        $inventoryItem = $this->owner->getInventoryItem();
        $inventoryLocationHandle = "default"; // This is unfortunately not stored in the project config - so I'm going to stick with the default handle for now to avoid confusion as we only have one store / inventory in this project
        $inventoryLocation = Plugin::getInstance()->getInventoryLocations()->getInventoryLocationByHandle($inventoryLocationHandle);
        if(is_null($inventoryLocation)) {
            throw new Exception("Couldn't find inventory location by handle '$inventoryLocationHandle'.");
        }

        $updateInventoryLevels = UpdateInventoryLevelCollection::make();
        $updateInventoryLevels->push(new UpdateInventoryLevel([
            'type' => 'onHand',
            'updateAction' => 'set',
            'inventoryItem' => $inventoryItem,
            'inventoryLocation' => $inventoryLocation,
            'quantity' => $qty,
            'note' => 'updated from code',
        ]));

        if(! Plugin::getInstance()->getInventory()->executeUpdateInventoryLevels($updateInventoryLevels)) {
            throw new Exception("Inventory could not be set!");
        }
        return true;
    } catch (Throwable $e) {
        Lyskomponenter::error("Couldn't update stock for variant! Error: {$e->getMessage()}");
        return false;
    }
}

I'm going to keep this discussion open, since I'm sure there are better ways to do this, or there will be eventually.

[hatyi]

Never mind it still doesn't work unfortunately. I'll update it later if I manage to figure it out. I believe I'm around the right path.