Doctrine - A new entity was found through the relationship

Question

since 2 weeks, we are having this problem while trying to flush new elements:

CRITICAL: Doctrine\\ORM\\ORMInvalidArgumentException:

A new

Answer 1

I got this error too when tried to add new entity.

A new entity was found through the relationship 'Application\Entity\User#chats' 
that was not configured to cascade persist operations for entity: ###. 
To solve this issue: Either explicitly call EntityManager#persist() on this unknown entity or
configure cascade persist  this association in the mapping for example @ManyToOne(..,cascade={"persist"}).

My case was that I tried to save entity, that shouldn't be saved. Entity relations was filled and tried to be saved (User has Chat in Many2Many, but Chat was a temporary entity), but there were some collisions.

So If I use cascade={"persist"} I get unwanted behaviour - trash entity is saved. My solution was to remove non-saving entity out of any saving entities:

// User entity code
public function removeFromChats(Chat $c = null){
    if ($c and $this->chats->contains($c)) {
        $this->chats->removeElement($c);
    }
}

Saving code

/* some code witch $chat entity */
$chat->addUser($user);

// saving
$user->removeFromChats($chat);
$this->getEntityManager()->persist($user);
$this->getEntityManager()->flush();