class EntityValidationException

class EntityValidationException extends MigrateException {
    
    /**
     * The separator for combining multiple messages into a single string.
     *
     * Afterwards, the separator could be used to split a concatenated string
     * onto multiple lines.
     *
     * @code
     * explode(EntityValidationException::MESSAGES_SEPARATOR, $messages);
     * @endcode
     */
    const MESSAGES_SEPARATOR = '||';
    
    /**
     * The list of violations generated during the entity validation.
     *
     * @var \Drupal\Core\Entity\EntityConstraintViolationListInterface
     */
    protected $violations;
    
    /**
     * EntityValidationException constructor.
     *
     * @param \Drupal\Core\Entity\EntityConstraintViolationListInterface $violations
     *   The list of violations generated during the entity validation.
     */
    public function __construct(EntityConstraintViolationListInterface $violations) {
        $this->violations = $violations;
        $entity = $this->violations
            ->getEntity();
        $locator = $entity->getEntityTypeId();
        if ($entity_id = $entity->id()) {
            $locator = sprintf('%s: %s', $locator, $entity_id);
            if ($entity instanceof RevisionableInterface && ($revision_id = $entity->getRevisionId())) {
                $locator .= sprintf(', revision: %s', $revision_id);
            }
        }
        // Example: "[user]: field_a=Violation 1., field_b=Violation 2.".
        // Example: "[user: 1]: field_a=Violation 1., field_b=Violation 2.".
        // Example: "[node: 19, revision: 12129]: field_a=Violation 1.".
        parent::__construct(sprintf('[%s]: %s', $locator, implode(static::MESSAGES_SEPARATOR, $this->getViolationMessages())));
    }
    
    /**
     * Returns the list of violation messages.
     *
     * @return string[]
     *   The list of violation messages.
     */
    public function getViolationMessages() {
        $messages = [];
        foreach ($this->violations as $violation) {
            assert($violation instanceof ConstraintViolationInterface);
            $messages[] = sprintf('%s=%s', $violation->getPropertyPath(), $violation->getMessage());
        }
        return $messages;
    }
    
    /**
     * Returns the list of violations generated during the entity validation.
     *
     * @return \Drupal\Core\Entity\EntityConstraintViolationListInterface
     *   The list of violations generated during the entity validation.
     */
    public function getViolations() {
        return $this->violations;
    }

}