Doctrine ORM 2.16+ makes a change to how the annotations and attribute mapping drivers report fields inherited from parent classes. For details, see doctrine/orm#10455. It will trigger a deprecation notice unless the new mode is activated. In ORM 3.0, the new mode will be the only one.
The new mode does not should not make a difference for regular, valid use cases, but may lead to MappingExceptions for users with certain configurations that were not meant to be supported by the ORM in the first place. To avoid surprising users (even when their configuration is invalid) during a 2.16 minor version upgrade, the transition to this new mode was implemented as an opt-in. This way, you can try and deal with the change any time you see fit.
In version 2.10+ of this bundle, a new configuration setting report_fields_where_declared was added at the entity manager configuration level. Set it to true to switch the mapping driver for the corresponding entity manager to the new mode. It is only relevant for mapping configurations using attributes or annotations.
Unless you set it to true, Doctrine ORM will emit deprecation messages mentioning this new setting.
Doctrine ORM 2.14+ adds support for validating the XSD of XML mapping files. In ORM 3.0, this validation will be mandatory.
As the ecosystem is known to rely on custom elements in the XML mapping files that are forbidden when validating the XSD (for instance when using gedmo/doctrine-extensions), this validation is opt-in thanks to a validate_xml_mapping setting at the entity manager configuration level.
Unless you set it to true, Doctrine ORM will emit deprecation messages mentioning the XSD validation.
Doctrine\Bundle\DoctrineBundle\EventSubscriber\EventSubscriberInterfacehas been deprecated. Use the#[AsDoctrineListener]attribute instead.