External DTOs should be usable as part of ExtensionAttributes system

[MeCapron]

Summary (*)

External classes such as DTO can not be used as part of extension attributes system if they are not arrays, because Magento2 will try to instantiate the object through the ObjectManager as if it was a \Magento\Framework\DataObject::class

Examples (*)

Example :

    <extension_attributes for="Magento\Customer\Api\Data\CustomerInterface">
        <attribute code="test1" type="MyVendor\Custom\DTO\MyDTOInterface[]"/>
        <attribute code="test2" type="MyVendor\Custom\DTO\AnotherDTO"/>
    </extension_attributes>

In this example, while calling :

       // $customerInformation = []; -> array with data information

        $this->dataObjectHelper->populateWithArray(
            $customer->getDataModel(),
            $customerInformation,
            CustomerInterface::class
        );

For the attribute test2 we will call :

• https://github.com/pepe1518/magento2/blob/master/vendor/magento/framework/Api/DataObjectHelper.php#L129
• Then https://github.com/pepe1518/magento2/blob/master/vendor/magento/framework/Api/DataObjectHelper.php#L205

As you see there, if the target type object is not part of the Magento "system" (i.e : not extending the DataObject class), it will not be created with the good data.

It leads the developer to duplicate the DTO class which is a non-sense because of the simplicity of such classes. Also, we could want to use direct DTO from external (vendor) modules such as SDK models.

Btw, it is counter-intuitive that we can define non DataObject extended objects in the extension_attributes.yml but they are not completely handled in the system. It made me think that this is just a specific (and marginal) forgotten case.

The same happens here : https://github.com/pepe1518/magento2/blob/master/vendor/magento/framework/Api/DataObjectHelper.php#L215

Proposed solution

We could implement this kind of solution which is what is done for array typed objects :

        if (is_subclass_of($extensionAttributeType, DataObject::class)) {
                $value[$extensionAttributeKey] = $this->objectFactory->create(
                        $extensionAttributeType,
                        ['data' => $extensionAttributeValue]
                );
        } else {
                $extensionAttributeInner = $this->objectFactory->create($extensionAttributeType, []);

                $this->populateWithArray(
                        $extensionAttributeInner,
                        $extensionAttributeValue,
                        $extensionAttributeType
                );

                $value[$extensionAttributeKey] = $extensionAttributeInner;
        }

Based on your suggestions/answers, I could make a PR for this.

Thanks,
Melvin

Below attached module helps in issue reproduction

Magz.zip

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[m2-assistant]

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[m2-assistant]

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[engcom-Lima]

Hi @MeCapron ,

Thank you for the collaboration and reporting the issue.
Can you please provide us with the exact steps to reproduce this issue.

Thanks!

[engcom-Lima]

Hi @MeCapron ,

We have noticed that this issue has not been updated for a period of 14 Days.
Hence we assume that this issue is fixed now, so we are closing it.Please raise a fresh ticket or reopen this ticket if you need more assistance on this.

Thanks

[MeCapron]

Hi @engcom-Lima,

I have opened a PR related on this issue and added a manual step reproduction with a repository :

1. Declare an extension attribute for the customer

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
    <extension_attributes for="Magento\Customer\Api\Data\CustomerInterface">
        <attribute code="loyaltyCards" type="Module\DataObject\Model\LoyaltyCard[]"/>
    </extension_attributes>
</config>

2. Define the class value, and its subchild :

The class LoyaltyCard

<?php

declare(strict_types=1);

namespace Module\DataObject\Model;

class LoyaltyCard
{
    private string $label;

    /**
     * @var \Module\DataObject\Model\Sub\Card[]
     */
    private array $cards;

    /**
     * @return string
     */
    public function getLabel(): string
    {
        return $this->label;
    }

    /**
     * @param string $label
     *
     * @return void
     */
    public function setLabel(string $label): void
    {
        $this->label = $label;
    }

    /**
     * @return \Module\DataObject\Model\Sub\Card[]
     */
    public function getCards(): array
    {
        return $this->cards;
    }

    /**
     * @param \Module\DataObject\Model\Sub\Card[] $cards
     *
     * @return void
     */
    public function setCards(array $cards): void
    {
        $this->cards = $cards;
    }
}

The card class

<?php

declare(strict_types=1);

namespace Module\DataObject\Model\Sub;

class Card
{
    private \Module\DataObject\Model\Sub\Nested\CardData $cardData;

    /**
     * @return \Module\DataObject\Model\Sub\Nested\CardData
     */
    public function getCardData(): \Module\DataObject\Model\Sub\Nested\CardData
    {
        return $this->cardData;
    }

    /**
     * @param \Module\DataObject\Model\Sub\Nested\CardData $cardData
     *
     * @return void
     */
    public function setCardData(\Module\DataObject\Model\Sub\Nested\CardData $cardData): void
    {
        $this->cardData = $cardData;
    }
}

The CardData class

<?php

declare(strict_types=1);

namespace Module\DataObject\Model\Sub\Nested;

class CardData
{
    private ?int $cardNumber = null;

    /**
     * @return int|null
     */
    public function getCardNumber(): ?int
    {
        return $this->cardNumber;
    }

    /**
     * @param int $cardNumber
     *
     * @return void
     */
    public function setCardNumber(int $cardNumber): void
    {
        $this->cardNumber = $cardNumber;
    }
}

Then create an observer to make your tests easier :

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="controller_action_predispatch">
        <observer name="test_dataobject" instance="Module\DataObject\Observer\TestDataObjectNestedObject"/>
    </event>
</config>

The observer

<?php

declare(strict_types=1);

namespace Module\DataObject\Observer;

use Magento\Customer\Api\Data\CustomerInterface;
use Magento\Customer\Api\Data\CustomerInterfaceFactory;
use Magento\Framework\Api\DataObjectHelper;
use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
use Module\DataObject\Model\LoyaltyCard;
use Module\DataObject\Model\Sub\Card;

class TestDataObjectNestedObject implements ObserverInterface
{
    private DataObjectHelper $dataObjectHelper;

    private CustomerInterfaceFactory $customerFactory;

    public function __construct(
        DataObjectHelper $dataObjectHelper,
        CustomerInterfaceFactory $customerFactory
    ) {
        $this->dataObjectHelper = $dataObjectHelper;
        $this->customerFactory = $customerFactory;
    }

    public function execute(Observer $observer): void
    {
        $customer = $this->customerFactory->create();

        $this->dataObjectHelper->populateWithArray(
            $customer,
            [
                'extension_attributes' => [
                    'loyaltyCards' => [
                        [
                            'label' => 'My first card',
                            'cards' => [
                                [
                                    'card_data' => [
                                        'card_number' => 157
                                    ]
                                ]
                            ]
                        ]
                    ]
                ]
            ],
            CustomerInterface::class
        );

        /** @var LoyaltyCard $loyaltyCard */
        $loyaltyCard = current($customer->getExtensionAttributes()->getLoyaltyCards());

        /** @var Card $innerCard */
        $innerCard = current($loyaltyCard->getCards());

        echo sprintf('The card number is %d', $innerCard->getCardData()->getCardNumber());
    }
}

As you see, even though the card number has been defined to 157 its value will be null or 0.

This is because of the way nested objects are created :

magento2/lib/internal/Magento/Framework/Api/DataObjectHelper.php

Line 235 in 3e5be99

$object = $this->objectFactory->create($returnType, $value);

They are created supposing that they have the values as arguments (in the constructor) which is not true every time.

After setting this fix, the value of the card number is now displayed 157. Because the current object we are trying to create is not a Magento\Framework\DataObject we will just instantiate it through the objectmanager and then we will fill this object with the same method.