Bridge/Symfony/Serializer/Normalizer/SaleItemNormalizer.php
private function getInStock(SaleItemInterface $item)
    {
        if (null === $subject = $this->subjectHelper->resolve($item, false)) {
            return INF;
        }

        if (!$subject instanceof StockSubjectInterface) {
            return INF;
        }

        if ($subject->isStockCompound()) {
            return INF;
        }

        if ($subject->getStockMode() === StockSubjectModes::MODE_DISABLED) {
            return INF;
        }

        return $subject->getInStock();
    }
private function getInStock(SaleItemInterface $item)
    {
        if (null === $subject = $this->subjectHelper->resolve($item, false)) {
            return INF;
        }

        if (!$subject instanceof StockSubjectInterface) {
            return INF;
        }

        if ($subject->isStockCompound()) {
            return INF;
        }

        if ($subject->getStockMode() === StockSubjectModes::MODE_DISABLED) {
            return INF;
        }

        return $subject->getInStock();
    }
Returns the item subject's in stock quantity.

@param SaleItemInterface $item

@return float