Symfony Form Collections: How to prevent duplicate INSERT on EntityManager->flush()? - php

Question

I have the following data model:
MainEntity.php
<?php declare(strict_type=1);
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity
*/
class MainEntity
{
// $id, etc...
/**
* #ORM\OneToMany(
* targetEntity="App\Entity\RelationEntity",
* mappedBy="mainEntity",
* cascade={"persist", "merge", "remove"},
* orphanRemoval=true
* )
*/
protected Collection $sideRelations;
// getSideRelations(), setSideRelations($relations), addSideRelation($sideRelation), removeSideRelation($sideRelation)...
}
RelationEntity.php
<?php declare(strict_types=1);
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity
* #ORM\Table(
* name="main_side_relation",
* uniqueConstraints={
* #ORM\UniqueConstraint(name="id_pair", columns={"main_entity_id", "side_entity_id"})
* }
* )
*/
class RelationEntity
{
// $id, etc...
/**
* #ORM\Column(type="integer", nullable=false)
*/
protected ?int $relationValue;
/**
* #ORM\ManyToOne(targetEntity="App\Entity\MainEntity", inversedBy="sideRelations")
* #ORM\JoinColumn(name="main_entity_id", referencedColumnName="id")
*/
protected MainEntity $mainEntity;
/**
* #ORM\ManyToOne(targetEntity="App\Entity\SideEntity", inversedBy="mainRelations")
* #ORM\JoinColumn(name="side_entity_id", referencedColumnName="id")
*/
protected SideEntity $sideEntity;
// getRelationValue(), setRelationValue($relationValue), getMainEntity(), setMainEntity($mainEntity), getSideEntity(), setSideEntity($sideEntity)...
}
SideEntity.php
<?php declare(strict_types=1);
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity
*/
class SideEntity
{
// $id, etc...
/**
* #ORM\OneToMany(
* targetEntity="App\Entity\RelationEntity",
* mappedBy="sideEntity",
* cascade={"persist", "merge", "remove"},
* orphanRemoval=true
* )
*/
protected Collection $mainRelations;
// getMainRelations(), setMainRelations($mainRelations), addMainRelation($mainRelation), removeMainRelation($mainRelation)...
I have existing Symfony form classes which I extended to fit the data model.
RelationEntityType.php
<?php declare(strict_types=1);
namespace App\Form;
class RelationEntityType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options): void
{
$builder
->add('relationValue', HiddenType::class)
->add('mainEntity', HiddenType::class)
->add('sideEntity', HiddenType::class)
;
// Add Transformers to switch between Entity and database ID for input value
}
public function configureOptions(OptionsResolverInterface $resolver): void
{
$resolver->setDefaults(['data_class' => RelationEntity::class]);
}
}
MainEntityType.php
<?php declare(strict_types=1);
namespace App\Form;
class MainEntityType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options): void
{
// ...
$builder->add('sideRelations', CollectionType::class, [
'required' => false,
'by_reference' => false,
'entry_type' => RelationEntity::class,
'allow_add' => true,
'allow_delete' => true,
'delete_empty' => true
]);
}
public function configureOptions(OptionsResolverInterface $resolver): void
{
$resolver->setDefaults(['data_class' => MainEntity::class]);
}
}
Submission works not as intended, as by using by_reference I explicitely remove and re-add existing unchanged collection entries, but when omitting the option it happens implicitly.
In both cases, UnitOfWork is filled with insertion queries for the already existing collection entries (and throws errors due to the unique constraint). I don't want that.
Symfony's form collection configuration docs doesn't yield valuable information on how to prevent collections from becoming "dirty" although their entries have technically not been changed.
How exactly do I avoid overwriting unchanged existing collection entries?
(If necessary, I can provide the remaining code for an MWE)