TYPO3 Core

Since the early days of extbase, it is possible to use a namespaced shorthand notation for extbase validators. As an example, TYPO3.CMS.Extbase:NotEmpty will be resolved as TYPO3\CMS\Extbase\Validation\Validator\NotEmptyValidator or Vendor.Extension:Custom will be resolved as \Vendor\MyExtension\Validation\Validator\CustomValidator.

The described namespaced shorthand notation has however never been documented and is most likely not used often in extensions. In order to simplify extbase ValidatorClassNameResolver class, the namespaced shorthand notation should be deprecatd.