How to deserialize a nested array of objects declared on the constructor via promoted properties, with Symfony Serializer?

Question

Take the following DTO classes:

class UserDTO {
    /**
     * @param AddressDTO[] $addressBook
     */
    public function __construct(
        public string $name,
        public int $age,
        public ?AddressDTO $billingAddress,
        public ?AddressDTO $shippingAddress,
        public array $addressBook,
    ) {
    }
}

class AddressDTO {
    public function __construct(
        public string $street,
        public string $city,
    ) {
    }
}

I'd like to serialize and deserialize them to/from JSON.

I'm using the following Serializer configuration:

$encoders = [new JsonEncoder()];

$extractor = new PropertyInfoExtractor([], [
    new PhpDocExtractor(),
    new ReflectionExtractor(),
]);

$normalizers = [
    new ObjectNormalizer(null, null, null, $extractor),
    new ArrayDenormalizer(),
];

$serializer = new Serializer($normalizers, $encoders);

But when serializing/deserializing this object:

$address = new AddressDTO('Rue Paradis', 'Marseille');
$user = new UserDTO('John', 25, $address, null, [$address]);

$jsonContent = $serializer->serialize($user, 'json');
dd($serializer->deserialize($jsonContent, UserDTO::class, 'json'));

I get the following result:

UserDTO^ {#54
  +name: "John"
  +age: 25
  +billingAddress: AddressDTO^ {#48
    +street: "Rue Paradis"
    +city: "Marseille"
  }
  +shippingAddress: null
  +addressBook: array:1 [
    0 => array:2 [
      "street" => "Rue Paradis"
      "city" => "Marseille"
    ]
  ]
}

When I would expect:

UserDTO^ {#54
  +name: "John"
  +age: 25
  +billingAddress: AddressDTO^ {#48
    +street: "Rue Paradis"
    +city: "Marseille"
  }
  +shippingAddress: null
  +addressBook: array:1 [
    0 => AddressDTO^ {#48
      +street: "Rue Paradis"
      +city: "Marseille"
    }
  ]
}

As you can see, $addressBook is deserialized as an array of array, instead of an array of AddressDTO. I expected the PhpDocExtractor to read the @param AddressDTO[] from the constructor, but this does not work.

It only works if I make $addressBook a public property documented with @var.

Is there a way to make it work with a simple @param on the constructor?

(Non-)working-demo: https://phpsandbox.io/n/gentle-mountain-mmod-rnmqd

---

What I've read and tried:

• Extract types of constructor parameters from docblock comment
• symfony deserialize nested objects
• How can I deserialize an array of objects in Symfony Serializer?

None of the proposed solutions seem to work for me.

Tamis

it looks right. you tried it in a symfony app with only inject the serializerInterface? – Concepcionconcept

@Concepcionconcept I'm using it standalone. I added a phpsandbox.io link to my question if you want to fiddle with it. – Tamis

Answer 1

Apparently the issue is that the PhpDocExtractor does not extract properties from constructors. You need to use a specific extractor for this:

use Symfony\Component\PropertyInfo;
use Symfony\Component\Serializer;

$phpDocExtractor = new PropertyInfo\Extractor\PhpDocExtractor();
$typeExtractor   = new PropertyInfo\PropertyInfoExtractor(
    typeExtractors: [ new PropertyInfo\Extractor\ConstructorExtractor([$phpDocExtractor]), $phpDocExtractor,]
);

$serializer = new Serializer\Serializer(
    normalizers: [
                    new Serializer\Normalizer\ObjectNormalizer(propertyTypeExtractor: $typeExtractor),
                    new Serializer\Normalizer\ArrayDenormalizer(),
                 ],
    encoders:    ['json' => new Serializer\Encoder\JsonEncoder()]
);

With this you'll get the desired results. Took me a bit to figure it out. The multiple denormalizer/extractor chains always get me.

---

Alternatively, for more complex os specialized situations, you could create your own custom denormalizer:

use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
use Symfony\Component\Serializer\Normalizer\DenormalizerAwareInterface;
use Symfony\Component\Serializer\Normalizer\DenormalizerAwareTrait

class UserDenormalizer
    implements DenormalizerInterface, DenormalizerAwareInterface
{

    use DenormalizerAwareTrait;

    public function denormalize($data, string $type, string $format = null, array $context = [])
    {
        $addressBook = array_map(fn($address) => $this->denormalizer->denormalize($address, AddressDTO::class), $data['addressBook']);

        return new UserDTO(
            name:            $data['name'],
            age:             $data['age'],
            billingAddress:  $this->denormalizer->denormalize($data['billingAddress'], AddressDTO::class),
            shippingAddress: $this->denormalizer->denormalize($data['shippingAddress'], AddressDTO::class),
            addressBook:     $addressBook
        );
    }

    public function supportsDenormalization($data, string $type, string $format = null)
    {
        return $type === UserDTO::class;
    }
}

Setup would become this:

$extractor = new PropertyInfoExtractor([], [
    new PhpDocExtractor(),
    new ReflectionExtractor(),
    
]);

$userDenormalizer = new UserDenormalizer();
$normalizers      = [
    $userDenormalizer,
    new ObjectNormalizer(null, null, null, $extractor),
    new ArrayDenormalizer(),

];
$serializer       = new Serializer($normalizers, [new JsonEncoder()]);
$userDenormalizer->setDenormalizer($serializer);

Output becomes what you would expect:

^ UserDTO^ {#39
  +name: "John"
  +age: 25
  +billingAddress: AddressDTO^ {#45
    +street: "Rue Paradis"
    +city: "Marseille"
  }
  +shippingAddress: null
  +addressBook: array:2 [
    0 => AddressDTO^ {#46
      +street: "Rue Paradis"
      +city: "Marseille"
    }
  ]
}

Misname

if I am using the symfony serializer as a dependency injection is it possible to add the extractor to the normalizer? – Nelidanelie

Answer 2

No need to manually compose the chain, the injected serialiser will support constructor param extractor automagically if the phpdocumentor/reflection-docblock package is installed. See this section in the docs

Midmost