trait EntityResourceValidationTrait

trait EntityResourceValidationTrait {
    
    /**
     * Verifies that an entity does not violate any validation constraints.
     *
     * The validation errors will be filtered to not include fields to which the
     * current user does not have access and if $fields_to_validate is provided
     * will only include fields in that array.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity to validate.
     * @param string[] $fields_to_validate
     *   (optional) An array of field names. If specified, filters the violations
     *   list to include only this set of fields.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\UnprocessableEntityHttpException
     *   If validation errors are found.
     */
    protected function validate(EntityInterface $entity, array $fields_to_validate = []) {
        // @todo Update this check in https://www.drupal.org/node/2300677.
        if (!$entity instanceof FieldableEntityInterface) {
            return;
        }
        $violations = $entity->validate();
        // Remove violations of inaccessible fields as they cannot stem from our
        // changes.
        $violations->filterByFieldAccess();
        if ($fields_to_validate) {
            // Filter violations by explicitly provided array of field names.
            $violations->filterByFields(array_diff(array_keys($entity->getFieldDefinitions()), $fields_to_validate));
        }
        if ($violations->count() > 0) {
            $message = "Unprocessable Entity: validation failed.\n";
            foreach ($violations as $violation) {
                // We strip every HTML from the error message to have a nicer to read
                // message on REST responses.
                $message .= $violation->getPropertyPath() . ': ' . PlainTextOutput::renderFromHtml($violation->getMessage()) . "\n";
            }
            throw new UnprocessableEntityHttpException($message);
        }
    }

}