Null in fields value in Cached Entity several times on day on high-load project.

[AlexSmerw]

Bug Report

Q	A
BC Break	yes
Version	2.6.3

Summary

We have a problem with the cache on a high-load project. Several times a day, the entity is retrieved from the cache with the field value = null, and these fields cannot be null

/ **
    * @var curator
    *
    * @ManyToOne (targetEntity = "SD \ Domain \ PersistModel \ Curator \ Curator")
    * @JoinColumn (name = "curator_id", referencedColumnName = "id")
    * /
   private $ curator ;

Current behavior

This situation arises from related entities. When the parent entity gets out of the cache, and the related is already expired.
See DefaultEntityHydrator function loadCacheEntry
Then
BasicEntityPersister function load will return Entity with null fields value.
Because AbstractEntityPersister
$entity = $this->persister->loadById($identifier, $entity);
It put $entity = null to function loadById($identifier, $entity) Instead Entity.

How to reproduce

Set $assocEntry = null on DefaultEntityHydrator line180 for child entity

Expected behavior

I think this can be corrected by editing the code in function loadById(array $identifier, $entity = null)
loadById

Replace $ entity with $ cachedEntity
https://github.com/doctrine/orm/blob/master/lib/Doctrine/ORM/Cache/Persister/Entity/AbstractEntityPersister.php#L458

$cachedEntity = $this->persister->loadById($identifier, $entity);
        if ($cachedEntity === null) {
            return null;
         }

[Ocramius]

We'd need a test case for this: as the issue is presented right now, this isn't really usable by maintainers.

[AlexSmerw]

Look. For example. We have 3 classes :
Car
Engine
Power
Link on code

Init data

$engine = new Car\Engine('turbo');
$power = new Car\Power(100, 110, $engine);
$car = new Car\Car('white', $engine);

$entityManger->persist($car);
$entityManger->persist($power);
$entityManger->persist($engine);

$entityManger->flush();

When entities have already set to cache, we try to get data from cache

$carRepository = $entityManger->getRepository(Car\Car::class);
$car = $carRepository->find(1);
$engine = $car->getEngine();

$engine short dump
isInitialized = false
model = null

$power = $engine->getPower(); // In this moment $assocRegion->get($assocKey) in Doctrine/ORM/Cache/DefaultEntityHydrator.php it can return null, because key 'power_hash' can be expired in hi load project.
It very rare situation, but we have this problem every days.

$engine short dump
isInitialized = true
model = null

$model = $engine->getModel(); - Exception 'Car\Engine::getModel() must be of th
e type string, null returned'

For problem reproduction when started code $power = $engine->getPower(); set debug breakpoint there $assocRegion->get($assocKey) in Doctrine/ORM/Cache/DefaultEntityHydrator.php. And wait while cache time is over. Then go ahead. As for me, I set regionLifeTime = 20 seconds.

[Ocramius]

Thanks for the more detailed explanation, but we'd still need an (automated) integration test that verifies the issue. See https://github.com/doctrine/orm/tree/master/tests/Doctrine/Tests/ORM/Functional for examples.

[lcobucci]

Handled by #7750