Magento 2.2 - Load eav attribute data for every product on collection load

Question

I've created a multiselect custom eav attribute based on a flat table, so I used a dataSource, for a product everything is working fine, API (SOAP & REST), display on the product page etc but I'd like to get the data inside a collection for the page_list.

Right now it's what i'm doing on the product page but if I have 500 products I have to do 500 requests to get the eav attributes data on the page_list.

    $product = $this->productRepository->getById($id);
        $attr = $product->getCustomAttribute("Flags");
        $flagContent = [];
        if ($attr && $attrValues = $attr->getValue()) {
            $flag = $this->flagsCollectionFactory->create();
            $flagContentObject = $flag->addFieldToFilter("flags_id", explode(",", $attrValues))->toArray();
            if ($flagContentObject["items"]) {
                $flagContent = $flagContentObject["items"];
            }
        }
        return $flagContent;

Is there any way to load this "Flags" EAV attribute when I load the product collection so I don't have to do a request for every loaded products on the page_list ?

Thanks

Answer 1

You can do it by following these steps, in your module you need to add catalog_attribute in etc/catalog_attributes.xml by this attribute will be loaded by default.

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Catalog:etc/catalog_attributes.xsd">
    <group name="catalog_product">
        <attribute name="attribute_code"/>
    </group>
</config>

Answer 2

You can create {MODULE_NAME}/etc/catalog_attributes.xml with such content:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Catalog:etc/catalog_attributes.xsd">
    <group name="catalog_product">
        <attribute name="MY_PRODUCT_ATTRIBUTE"/>
    </group>
</config>

Please see the following file for more info:

/vendor/magento/module-catalog/etc/catalog_attributes.xml