DoctrineBridgeBundle | provides annotations for interlinking entities | Web Framework library

In my Symfony application, when creating or updating a certain entity, I would like to check whether a duplicate entity already exists, and if it does, display an URL to the existing entity's page together with the error message.

I use Symfony's Validator component with custom constraint classes for my validation, to have reusable validators in different parts of the application - the web controller, console commands, batch processing scripts, etc. I would like $validator->validate($entity) to validate entity uniqueness as well, using a custom UniqueEntityConstraint

However, I cannot find a way to do this - there doesn't appear to be any way to pass an object from a Constraint Validator back to the controller.

Is there a way to do what I need using the Validator component, or am I at a dead end?

Solutions I've explored so far:

1. DoctrineBridgeBundle's UniqueEntity constraint.

Doesn't return the existing entity or even its ID, just a message that it exists.

1. Extend ConstraintViolation with a getDuplicateEntity() method.

This would be the optimal solution, but it doesn't work - there appears to be no way to use a custom class without overriding core Symfony code.

1. Store the duplicate entity on the Constraint itself and retrieve it using $violation->getConstraint()->getDuplicateEntity().

It would be a dirty hack even if it worked, but it doesn't - ConstraintValidators reuse the same Constraint instance, so if you were validating multiple entities in a row, getDuplicateEntity() would only get you the last duplicate from the batch.