Override association mapping of a trait property in Doctrine 2.6

Question

Prerequisites:

• PHP 7.1.8
• Symfony 3.3.9
• Doctrine 2.6.x-dev

I wonder if it's possible to override an inversedBy attribute of a property association mapping that's taken from a trait.

An interface that I use as a concrete user entity placeholder:

ReusableBundle\ModelEntrantInterface.php

interface EntrantInterface
{
    public function getEmail();

    public function getFirstName();

    public function getLastName();
}

1. The following architecture works just fine (need to create User entity that implements EntrantInterface and all other entities that are derived from these abstract classes in AppBundle):

ReusableBundle\Entity\Entry.php

/**
 * @ORM\MappedSuperclass
 */
abstract class Entry
{
    /**
     * @var EntrantInterface
     *
     * @ORM\ManyToOne(targetEntity="ReusableBundle\Model\EntrantInterface", inversedBy="entries")
     * @ORM\JoinColumn(name="user_id")
     */
    protected $user;

    // getters/setters...
}

ReusableBundle\Entity\Timestamp.php

/**
 * @ORM\MappedSuperclass
 */
abstract class Timestamp
{
    /**
     * @var EntrantInterface
     *
     * @ORM\ManyToOne(targetEntity="ReusableBundle\Model\EntrantInterface", inversedBy="timestamps")
     * @ORM\JoinColumn(name="user_id")
     */
    protected $user;

    // getters/setters...
}

And couple more entities with similar structure that utilize EntranInterface

2. And this is what I want to achieve - UserAwareTrait to be reusable across several entities:

ReusableBundle\Entity\Traits\UserAwareTrait.php

trait UserAwareTrait
{
    /**
     * @var EntrantInterface
     *
     * @ORM\ManyToOne(targetEntity="ReusableBundle\Model\EntrantInterface")
     * @ORM\JoinColumn(name="user_id")
     */
    protected $user;

    // getter/setter...
}

In Doctrine 2.6 if I would use super class and wanted to override its property I'd do this:

/**
 * @ORM\MappedSuperclass
 * @ORM\AssociationOverrides({
 *     @ORM\AssociationOverride({name="property", inversedBy="entities"})
 * })
 */
abstract class Entity extends SuperEntity
{
    // code...
}

But if I want that Entity to use UserAwareTrait and override association mapping of a property...

/**
 * @ORM\MappedSuperclass
 * @ORM\AssociationOverrides({
 *     @ORM\AssociationOverride({name="user", inversedBy="entries"})
 * })
 */
abstract class Entry
{
    use UserAwareTrait;
    // code...
}

... and run php bin/console doctrine:schema:validate I see this error in the console:

[Doctrine\ORM\Mapping\MappingException]
Invalid field override named 'user' for class 'ReusableBundle\Entity\Entry'.

Is there a workaround that I could follow to achieve the desired result?

1. Use trait to store shared properties

2. Override assotiation mapping or (possibly) attributes mapping in the class that uses that trait

Answer 1

TL;DR You should change the access modificator from protected to private. Don't forget that you will not be able to directly manipulate the private property in a subclass and will need a getter.

The exception appears due to the bug (I believe, or a quirk of the behavior) in the AnnotationDriver.

foreach ($class->getProperties() as $property) {
    if ($metadata->isMappedSuperclass && ! $property->isPrivate()
        ||
        ...) {
        continue;
    }

It skips all non-private properties for MappedSuperclass letting them to compose metadata on the subclass parsing. But when it comes to overriding the driver tries to do it at a MappedSuperclass level, it doesn't remember that the property was skipped, fails to find it in the metadata and raise an exception.

I made a detailed explanation at the issue. You can find there also the link to the unit tests that highlight the case.