app/bundles/LeadBundle/Field/IdentifierFields.php

<?php

declare(strict_types=1);

namespace Mautic\LeadBundle\Field;

use Mautic\LeadBundle\Entity\Company;
use Mautic\LeadBundle\Entity\IdentifierFieldEntityInterface;
use Mautic\LeadBundle\Entity\Lead;

class IdentifierFields
{
    public function __construct(
        private FieldsWithUniqueIdentifier $fieldsWithUniqueIdentifier,
        private FieldList $fieldList
    ) {
    }

    /**
     * @return string[]
     */
    public function getFieldList(string $object, ?object $entityClass = null): array
    {
        return array_merge(
            $this->getDefaultFields($object, $entityClass),
            $this->getUniqueIdentifierFields($object),
            $this->getSocialFields($object)
        );
    }

    /**
     * @return string[]
     */
    private function getDefaultFields(string $object, ?object $entityClass): array
    {
        if (null === $entityClass) {
            switch ($object) {
                case 'lead':
                    $entityClass = Lead::class;
                    break;
                case 'company':
                    $entityClass = Company::class;
                    break;
                default:
                    return [];
            }
        }

        if (is_subclass_of($entityClass, IdentifierFieldEntityInterface::class)) {
            return $entityClass::getDefaultIdentifierFields();
        }

        // The class wasn't recognized or doesn't implement the interface
        return [];
    }

    /**
     * @return string[]
     */
    private function getUniqueIdentifierFields(string $object): array
    {
        $fields = $this->fieldsWithUniqueIdentifier->getFieldsWithUniqueIdentifier(
            [
                'object' => $object,
            ]
        );

        return array_keys($fields);
    }

    /**
     * @return string[]
     */
    private function getSocialFields(string $object): array
    {
        $fields = $this->fieldList->getFieldList(
            true,
            false,
            [
                'isPublished' => true,
                'object'      => $object,
            ]
        );

        if (!isset($fields['Social'])) {
            return [];
        }

        return array_keys($fields['Social']);
    }
}