Uninitialized proxies cannot be serialized properly

I have the following entity:

class Currency
{
    /** @Id @Column(type="string") */
    protected $code;
        
    /** @Column(type="string") */    
    protected $name;
}

When I serialize an object graph which references a Currency proxy, but this proxy is initialized, then this works as expected:

O:65:"Application\Domain\Proxy\__CG__\Application\Domain\Model\Currency":3:{s:17:"__isInitialized__";b:1;s:7:"*code";s:3:"USD";s:7:"*name";s:20:"United States Dollar";}

However, if the proxy is not initialized, then all properties are serialized as null, and the identity is lost:

O:65:"Application\Domain\Proxy\__CG__\Application\Domain\Model\Currency":3:{s:17:"__isInitialized__";b:0;s:7:"*code";N;s:7:"*name";N;}

That makes a merge() impossible once stored in a session, as the identity of the entity is now unknown.

I think the solution might be:

• either to have the proxy's $_identity field serialized as well
• or to have the $code (identity field) populated when the proxy is created.