Symfony 3 UniqueEntity validation on update - symfony

Question

I am facing an issue with UniqueEntity validation.
I have a field "internal_asset_number" which should be unique and it's working fine on create. On update when i edit the existing current data with the same values, it shows "There is already an asset with that internal number!" but it shouldn't because it's the same entry.
The entity:
/**
* Asset
*
* #ORM\Table(schema="assets", name="asset", uniqueConstraints= {#ORM\UniqueConstraint(name="uk_asset_internal_asset_number_client_id", columns={"internal_asset_number", "client_id"})})
* #ORM\Entity(repositoryClass="Api\AssetBundle\Entity\AssetRepository")
* #UniqueEntity(fields={"internalAssetNumber"}, groups={"post", "put"}, message="There is already an asset with that internal number!")
*/
class Asset
{
/**
* #var guid
*
* #ORM\Column(name="id", type="string")
* #ORM\Id
* #ORM\GeneratedValue(strategy="UUID")
*/
private $id;
/**
* #var string
*
* #ORM\Column(name="client_id", type="string", length=255, nullable=false)
*/
private $clientId;
/**
* #var string
*
* #ORM\Column(name="internal_asset_number", type="string", length=255, nullable=true, unique=true)
*/
private $internalAssetNumber;
Update method:
public function putAssetAction(Request $request, $id)
{
$data = $this->deserializer('Api\AssetBundle\Entity\Asset', $request, 'put');
if ($data instanceof \Exception) {
return View::create(['error' => $data->getMessage()], 400);
}
$validator = $this->get('validator');
$errors = $validator->validate($data, null, 'put');
if (count($errors) > 0) {
$errorsResponse = [];
foreach ($errors as $error) {
$errorsResponse = $error->getMessage();
}
return View::create(array('error' => $errorsResponse), 400);
}
...

Answer 1

As #xabbuh commented, the problem is that the entity you persist after update is not retrieved through the entityManager so when you persist it the entity manager thinks it is a new entity.
Here is how to solve it:
$entityManager->merge($entity);
This will tell the entitymanager to merge your serialized entity with the managed one
Some more explanation on merge():
https://stackoverflow.com/a/15838232/5758328