Call to Member function on null (plugin help)

Question

I currently have this Plugin, which is just this at the moment:

di.xm

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Quote\Model\Quote\Item">
      <plugin name="weight_override" type="Ibex\Options\Model\Plugin\Weight" sortOrder="1" />
    </type>
</config>

Weight.php

namespace Ibex\Options\Model\Plugin;

use Magento\Quote\Model\Quote;

class Weight
{

    public function beforeSetProduct(\Magento\Quote\Model\Quote\Item $subject, $product)
    {
        // logging to test override
        $logger = \Magento\Framework\App\ObjectManager::getInstance()->get('\Psr\Log\LoggerInterface');
        $logger->debug('Test');
        $weight = $product->getWeight();
        $logger->debug($weight);
        return $product;
    }
}
?>

Nothing fancy yet, and the debugging is working. However, it's causing this error at the moment:

PHP Fatal error:  Uncaught Error: Call to a member function setStoreId() on null in /pro/vendor/magento/module-quote/Model/Quote/Item.php:425
Stack trace:
#0 /pro/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Quote\Model\Quote\Item->setProduct(NULL, 'cat_p', 'catalog_product', 'product', false, Object(Magento\Catalog\Model\Product\Type\Simple), 
Object(Magento\Catalog\Model\Product\Link\Proxy), Array, Object(Magento\Catalog\Model\Product\Url), Array, 
Object(Magento\Catalog\Model\Product\OptionFactory), NULL, NULL, true, true, Object(Magento\Catalog\Helper\Product), Object(Magento\Framework\Module\Manager), 
Object(Magento\Framework\Data\CollectionFactory), Object(Magento\Catalog\Model\Product\Type\Interceptor), Object(Magento\Catalog\Model\Product\Media\Config), 
Object(Magento\Catalog\Model\Product\Attribute\Source\Status\Proxy), Object(Magento\Catalog\Model\Product\Visibility), 
Object(Magento\CatalogInventory\Api\Data\StockItemInterfaceFactory), 
Object(Magento\Catal in /pro/vendor/magento/module-quote/Model/Quote/Item.php on line 425

And for some context, here's the chunk of the core file that's referenced:

  public function setProduct($product)
    {
        if ($this->getQuote()) {
            $product->setStoreId($this->getQuote()->getStoreId());
            $product->setCustomerGroupId($this->getQuote()->getCustomerGroupId());
        }
        $this->setData('product', $product)
            ->setProductId($product->getId())
            ->setProductType($product->getTypeId())
            ->setSku($this->getProduct()->getSku())
            ->setName($product->getName())
            ->setWeight($this->getProduct()->getWeight())
            ->setTaxClassId($product->getTaxClassId())
            ->setBaseCost($product->getCost());

        $stockItem = $product->getExtensionAttributes()->getStockItem();
        $this->setIsQtyDecimal($stockItem ? $stockItem->getIsQtyDecimal() : false);

        $this->_eventManager->dispatch(
            'sales_quote_item_set_product',
            ['product' => $product, 'quote_item' => $this]
        );

        return $this;
    }

What could be causing this error?

Answer 1

The return in your plugin function beforeSetProduct() needs to be an array. Please change as follows:

return [$product];