Doctrine preUpdate event shows no changeset for associated collections - php

Question

This is a question about the event system in Doctrine (within a Symfony project).
I have two classes, User and Visit, that are associated via a many-to-many relationship. I.e. a user can have many visits and a visit can have many users (that attend the visit).
class Visit
{
#[ORM\Column]
protected string $Date;
#[ORM\ManyToMany(targetEntity: User::class, inversedBy: "Visits")]
#[ORM\JoinTable(name: "users_visits")]
protected Collection $Users;
public function __construct()
{
$this->Users = new ArrayCollection();
}
//... other properties and methods omitted
}
class User
{
#[ORM\Column]
protected string $Name;
#[ORM\ManyToMany(targetEntity: Visit::class, inversedBy: "Users")]
#[ORM\JoinTable(name: "users_visits")]
protected Collection $Visits;
public function __construct()
{
$this->Visits = new ArrayCollection();
}
//... other properties and methods omitted
}
I also have an UpdateSubscriber that is supposed to record certain inserts, updates or removals, in a separate sql-table to create an overview over all relevant changes later on.
class UpdateSubscriber implements EventSubscriberInterface
{
public function __construct(private LoggerInterface $logger)
{
}
public function getSubscribedEvents(): array
{
return [
Events::preUpdate,
Events::postPersist,
Events::postRemove,
Events::postFlush
];
}
public function preUpdate(PreUpdateEventArgs $args): void
{
$this->logger->debug('Something has been updated');
if($args->hasChangedField('Date')){
$this->logger->debug('The date has been changed.');
}
if($args->hasChangedField('Users')){
$this->logger->debug('It was the Users field');
}
}
// ... other methods emitted
I have gotten this system to work, but when I run this test code
$visitRepo = $this->om->getRepository(Visit::class);
$userRepo = $this->om->getRepository(User::class);
// you can assume that visit 7 and user 8 already exist in the database
$v = $visitRepo->find(7);
$u = $userRepo->find(8);
$v->setDate('2022-01-05');
$this->om->flush();
$v->addUser($u);
$this->om->flush();
The test code works without errors and I can see a new row in the sql-table "users_visits". I can also see the date for visit 7 has been changed to 2022-01-05.
BUT: Checking the log I can only find
Something has been updated.
The date has been changed.
Something has been updated.
There is no "It was the Users field". Using my debugging tools I can see that the EntityChangeSet is empty during preUpdate() during the $v->addUser($u), which is weird and unexpected.
I have extensively been reading the docs for the event PreUpdate but there is no mentioning of why changes to associated collections are not shown in the EntityChangeSet or how I could track those changes in an EventSubscriber.
Do I have to go via the rather cumbersome UnitOfWork during the onFlushEvent? Or this there something I have been missing?

Answer 1

In case I myself or somebody else reads this, my pretty dirty solution was to collect all currently updated collections and then check if the property ("Users" in this case) matched on of these.
$updatedCollectionNames = array_map(
function (PersistentCollection $update) {
return $update->getMapping()['fieldName'];
},
$args->getEntityManager()->getUnitOfWork()->getScheduledCollectionUpdates()
);
// and later
if (in_array('Users', $updatedCollectionNames, true)){
$this->logger->debug('It was the Users field');
}
This seems dirty and contrived, but it will do for now until somebody has a better proposal.