Serialization of nested array of objects using constructor denormalization

[sadokmtir]

Symfony version(s) affected: 4.0.6

Description
So, let's say I have a JSON data corresponding to a class Child that has an attribute games that is an array of objects of class Game. So when using the serialisation using setters I get and the end a Child Object with an attribute games that is an array of several Game instances.
However for design reasons it is not possible to use the setters so I had to use the serialisation through the constructor, hence on my constructor I have someting like:

class Child
{

/**
     * @var Game[]
     */
    private $games;

   /**
     * Child constructor.
     *
     * @param Game[] $games
     */
    public function __construct(
        array $games,
    ) {
        $this->games = $games;
    }
 }

setter denormalization

The problem here is that the denormalizer could not figure out that the games is an array of objects from the class Game and then I get instead of an object an array have the same attributes defined on the Game class which is not the same when I add a setter for the games.

When I debug it the code fro both setter serialization and constructor serialization I can see the difference between both methods getting into action.

• For the first case of the setter denormalization the function validateAndDenormalize from the AbstractObjectNormalizer is handling the normalization and there is the code there is a check on the collection type if ($type->isCollection() && null !== ($collectionValueType = $type->getCollectionValueType()) && Type::BUILTIN_TYPE_OBJECT === $collectionValueType->getBuiltinType()) which can determine if the array has objects from a defined class.

Adding a setter like that is enough to get the right denormalization:

      /**
      * @param Game[] $games
      * @return Child
     */
     public function setGames(array $games): Child
     {
         $this->games = $games;
        return $this;
     }

constructor denormalization

• However for the other case: the constructor denormalization: the function instatiateObject from the AbstractNormalizer class is being executed and there there are no check on the type collection $params[] = $parameterData; ==> that line exactly is responsible of giving me back an array of attributes instead of creating an object from the class Game which I really found a bad behaviour and mis-leading.

How to reproduce
Just setting a Child class with an attribute games which is an array of Game objects. And a class Game with some attributes. And then A Json Object that represents a child objects with a related array of games is enough to reproduces this behaviour.
A hint for the JSON:

{
	"name": "test-boy",
	"age": 12,
	"games": [{
		"name": "Age of Empire",
		"genre": "Strategy"
	}]

}

Possible Solution
The possible solution is to implement a collection verification as it is implemented on the first case (setter denormalization) would be enough I guess to fix this behaviour.

[msolhao]

Symfony Serializer v4.1 is also affected.

[rdavaillaud]

maybe a duplicate of #25524

[Simperfit]

@xabbuh I think this is a dupplicate of #25524