Using Entity as Factory for Value Object

DormerType.php

<?php

abstract class DormerType implements DormerTypeInterface
{}

DormerTypeInterface.php

<?php

interface DormerTypeInterface
{
    public function canHaveGutterInstalled(): bool;
}

FlatDormerType.php

<?php

class FlatRoofDormer extends DormerType
{
    public function canHaveGutterInstalled(): bool
    {
        return true;
    }
}

Version 1:

<?php

final class Dormer
{
    /** @var DormerType $type */
    private $type;

    public static function construct(DormerType $type)
    {
        $this->type = $type;
    }

    public function addGutter(Gutter $gutter)
    {
        if (!$this->type->canHaveGutterInstalled()) {
            throw new DormerTypeCannotHaveGutterInstalledException();
        }
 
       $this->gutter = $gutter;
    }
}

final class DormerCalculationFactory extends AbstractCalculator
{
    private $dormerTypeRepository;

    public function createWithDto(CalculateDormerCommand $dto)
    {
        $dormerType = $this->dormerTypeRepository->ofId(DormerTypeId::fromInteger($dto->dormerTypeId));

        /** @var Dormer $dormer */
        $dormer = Dormer::construct($dormerType);
        $dormer->addGutter(Gutter::fromDto($dto->gutter));
    }
}

Version 2:

<?php

class DormerType()
{
    private $id;

    public function calculateDormer(Gutter $gutter)
    {
         if (!$this->canHaveGutterInstalled()) {
            throw new DormerTypeCannotHaveGutterInstalledException();
        }
       
        return new Dormer($this->id(), $gutter);
    }
}

Version 3:

final class DormerCalculationFactory extends AbstractCalculator
{
    private $dormerTypeRepository;

    public function createWithDto(CalculateDormerCommand $dto)
    {
        $dormerType = $this->dormerTypeRepository->ofId(DormerTypeId::fromInteger($dto->dormerTypeId));

        /** @var Dormer $dormer */
        $dormer = Dormer::construct($dormerType->id());

        if (null !== $dto->gutter && $dormerType->canHaveGutterInstalled()) {
            $dormer->addGutter(Gutter::fromDto($dto->gutter));
        }
    }
}

Since DormerType is an Entity I like the idea of only passing the DormerTypeId in Version 2.

After reading the following post on @culttt by @philipbrown I added a Version 3 with a pure factory.

Due to the coupled nature of the Factory and the object, it is usually fine to allow the Factory to protect the invariants of the object.

• https://www.culttt.com/2014/12/24/factories-domain-driven-design/

At the bottom line versions 1 and 2 "enforce" the invariants. A guttercan not be added to a DormerType that does not support it.
Version 3 protects the invariants but a developer could still create a Dormer by passing any type and any gutter.

But is this a requirement at all - protecting an object from inconsistently being created by the developer?

Version 3 "feels right".

What are your thoughts on this?

Discussion continued on phpddd:

• webdevilopers/php-ddd#34