Can't seem to override orm constraint mapping

[jenkoian]

tl;dr Overriding config/validation/orm.xml into my custom bundle (as talked about here http://symfony.com/doc/master/cookbook/bundles/inheritance.html#overriding-resources-templates-routing-validation-etc) doesn't seem to work.

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I need to set a custom repositoryMethod for the UniqueEntity constraint on the emailCanonical field (https://github.com/FriendsOfSymfony/FOSUserBundle/blob/master/Resources/config/validation/orm.xml#L18). The easiest way to do this I thought was to override the validation file as described in the tl;dr above. However, doing so doesn't seem to work.

I can override the file config/validation.xml and indeed add my custom constraint mapping within this, however because of the ValidationCompilerPass it does not replace the constraint within config/validation/orm.xml but just adds another. Disabling the compiler pass within the FOSUserBundle makes it do what I want.

Is the ValidationPass stopping these files from being overridden or should I be trying to override this constraint in a different manner?

[mvrhov]

It's a framework limitation: symfony/symfony#3224

[jenkoian]

Thanks @mvrhov that is exactly the problem I'm encountering. Have got around it with validation groups but it isn't ideal.