Symfony OneToMany with associative array : new row inserted instead of update - symfony

Question

I have to internationalize an app and particularly an entity called Program. To do so, I created an other entity ProgramIntl which contains a "locale" attribute (en_GB, fr_FR, etc) and strings which must be internationalized. I want the programIntl attribute in Program to be an associative array (with locale as key).
We have an API to read/write programs. GET and POST works fine but when I want to update data (PUT), the programIntl is not updated: an insert query is launched (and fails because of the unique constraint, but that's not the question).
Here is the code:
In Program.php:
/**
* #var
*
* #ORM\OneToMany(targetEntity="ProgramIntl", mappedBy="program", cascade={"persist", "remove", "merge"}, indexBy="locale", fetch="EAGER")
* #ORM\JoinColumn(nullable=false, onDelete="cascade")
* #Groups({"program_read", "program_write"})
*/
private $programIntl;
public function addProgramIntl($programIntl)
{
$this->programIntl[$programIntl->getLocale()] = $programIntl;
$programIntl->setProgram($this);
return $this;
}
public function setProgramIntl($programIntls)
{
$this->programIntl->clear();
foreach ($programIntls as $locale => $programIntl) {
$programIntl->setLocale($locale);
$this->addProgramIntl($programIntl);
}
}
public function getProgramIntl()
{
return $this->programIntl;
}
In ProgramIntl.php:
/**
* #ORM\Entity(repositoryClass="App\Repository\ProgramIntlRepository")
* #ORM\Table(name="program_intl",uniqueConstraints={#ORM\UniqueConstraint(name="program_intl_unique", columns={"program_id", "locale"})})
*/
class ProgramIntl
{
/**
* #ORM\Id()
* #ORM\GeneratedValue()
* #ORM\Column(type="integer")
* #Groups({"program_read", "program_write"})
*/
private $id;
/**
* #ORM\ManyToOne(targetEntity="App\Entity\Program", inversedBy="programIntl")
* #ORM\JoinColumn(nullable=false)
*/
private $program;
/**
* #ORM\Column(type="string", length=5, options={"fixed" = true})
*/
private $locale;
/**
* #ORM\Column(type="string", length=64)
* #Assert\NotBlank()
* #Groups({"program_read", "program_write"})
*/
private $some_attr;
/* ... */
}
Any idea of what could be the reason of the "insert" instead of "update" ?
Thanks

Answer 1

I forgot to mention that we use api-platform.
But I found the solution myself. In case anyone is interested, adding the following annotation to classes Program and ProgramIntl solved the problem:
/* #ApiResource(attributes={
* "normalization_context"={"groups"={"program_read", "program_write"}},
* "denormalization_context"={"groups"={"program_read", "program_write"}}
* }) */