Applying domain events to aggregate roots when deserializing payload of old events break current value object constraint changes

FirstName.php

<?php

/**
 * All characater were allowed in the initial value object.
 */
final class FirstName_V1
{
    /** @var string $name */
    private $name;

    private function __construct(string $aName)
    {
        $name = NameNormalizer::withString($aName);

        $this->name = $name;
    }

    public static function fromString(string $name): FirstName
    {
        return new self($name);
    }

    public function toString(): string
    {
        return $this->name;
    }
}

/**
 * Character e.g. numbers were forbidden.
 */
final class FirstName_V2
{
    /** @var string $name */
    private $name;

    private function __construct(string $aName)
    {
        $name = NameNormalizer::withString($aName);

        if (!NamePolicy::isSatisfiedBy($name)) {
            throw new NameContainsIllegalCharacters();
        }

        $this->name = $name;
    }

    public static function fromString(string $name): FirstName
    {
        return new self($name);
    }

    public function toString(): string
    {
        return $this->name;
    }
}

NameChanged.php

<?php

final class NameChanged extends AggregateChanged
{
    /** @var PersonId */
    private $personId;

    /** @var FirstName */
    private $firstName;
  
    public static function with(PersonId $personId, FirstName $oldFirstName, FirstName $newFirstName): NameChanged
    {
        $event = self::occur(
            $personId->toString(),
            [
                'personId' => $personId->toString(),
                'oldFirstName' => $oldFirstName->toString(),
                'newFirstName' => $newFirstName->toString(),
            ]
        );
        $event->personId = $personId;
        $event->oldFirstName = $oldFirstName;
        $event->newFirstName = $newFirstName;

        return $event;
    }
    
    public function personId(): PersonId
    {
        if (null === $this->personId) {
            $this->personId = PersonId::fromString($this->aggregateId());
        }

        return $this->personId;
    }

    public function newFirstName(): FirstName
    {
        if (null === $this->newFirstName) {
            $this->newFirstName = FirstName::fromString($this->payload['newFirstName']);
        }

        return $this->newFirstName;
    }  
}

Person.php

<?php

final class Person extends AggregateRoot
{
    /** @var PersonId */
    private $personId;

    /** @var FirstName */
    private $firstName;

    public function changeName(FirstName $newName): void
    {
        if ($newName->equalsTo($this-firstName)) {
            return;
        }
      
        $this->recordThat(NameChanged::with($this->personId, $this->firstName, $newName));
    }
  
    protected function apply(AggregateChanged $event): void
    {
        switch (get_class($event)) {
            case NameChanged::class:
                /** @var NameChanged $event */
                $this->firstName = $event->newFirstName();

                break;
        }
    }
}

Discussion moved to:

• webdevilopers/php-ddd#42