app/bundles/CoreBundle/Model/VariantModelTrait.php

<?php

namespace Mautic\CoreBundle\Model;

use Mautic\CoreBundle\Entity\TranslationEntityInterface;
use Mautic\CoreBundle\Entity\VariantEntityInterface;

trait VariantModelTrait
{
    /**
     * @var bool
     */
    protected $inConversion = false;

    /**
     * Converts a variant to the main item and the original main item a variant.
     */
    public function convertVariant(VariantEntityInterface $entity): void
    {
        // let saveEntities() know it does not need to set variant start dates
        $this->inConversion = true;

        [$parent, $children] = $entity->getVariants();

        $save = [];

        // set this email as the parent for the original parent and children
        if ($parent) {
            if ($parent->getId() != $entity->getId()) {
                if (method_exists($parent, 'setIsPublished')) {
                    $parent->setIsPublished(false);
                }

                $entity->addVariantChild($parent);
                $parent->setVariantParent($entity);
            }

            $parent->setVariantStartDate(null);
            $parent->setVariantSentCount(0);

            foreach ($children as $child) {
                // capture child before it's removed from collection
                $save[] = $child;

                $parent->removeVariantChild($child);
            }
        }

        if (count($save)) {
            foreach ($save as $child) {
                if ($child->getId() != $entity->getId()) {
                    if (method_exists($child, 'setIsPublished')) {
                        $child->setIsPublished(false);
                    }

                    $entity->addVariantChild($child);
                    $child->setVariantParent($entity);
                } else {
                    $child->removeVariantParent();
                }

                $child->setVariantSentCount(0);
                $child->setVariantStartDate(null);
            }
        }

        $save[] = $parent;
        $save[] = $entity;

        // save the entities
        $this->saveEntities($save, false);
    }

    /**
     * Prepare a variant for saving.
     *
     * @param array $resetVariantCounterMethods ['setVariantHits', 'setVariantSends', ...]
     */
    protected function preVariantSaveEntity(VariantEntityInterface $entity, array $resetVariantCounterMethods = [], \DateTime $variantStartDate = null): bool
    {
        $isVariant = $entity->isVariant();

        if (!$isVariant && $entity instanceof TranslationEntityInterface) {
            // Translations could be assigned to a variant and thus applicable to be reset
            if ($translationParent = $entity->getTranslationParent()) {
                $isVariant = $translationParent->isVariant(); /** @phpstan-ignore-line @todo for M6, extend the TranslationEntityInterface from The VariantEntityInterface */
            }
        }

        if ($isVariant) {
            // Reset the variant hit and start date if there are any changes and if this is an A/B test
            // Do it here in addition to postVariantSave() so that it's available to the event listeners
            $changes = $entity->getChanges();

            // If unpublished and wasn't changed from published - don't reset
            if (!$entity->isPublished(false) && (!isset($changes['isPublished']))) {
                return false;
            }

            // Reset the variant
            if (!empty($changes) && empty($this->inConversion)) {
                if (method_exists($entity, 'setVariantStartDate')) {
                    $entity->setVariantStartDate($variantStartDate);
                }

                // Reset counters
                foreach ($resetVariantCounterMethods as $method) {
                    if (method_exists($entity, $method)) {
                        $entity->$method(0);
                    }
                }

                return true;
            }
        }

        return false;
    }

    /**
     * Run post saving a variant aware entity.
     *
     * @param bool  $resetVariants
     * @param array $relatedIds
     */
    protected function postVariantSaveEntity(VariantEntityInterface $entity, $resetVariants = false, $relatedIds = [], \DateTime $variantStartDate = null)
    {
        // If parent, add this entity as a child of the parent so that it populates the list in the tab (due to Doctrine hanging on to entities in memory)
        if ($parent = $entity->getVariantParent()) {
            $parent->addVariantChild($entity);
        }

        // Reset associated variants if applicable due to changes
        if ($resetVariants && empty($this->inConversion)) {
            $this->resetVariants($entity, $relatedIds, $variantStartDate);
        }
    }

    protected function resetVariants($entity, $relatedIds = null, \DateTime $variantStartDate = null)
    {
        $repo = $this->getRepository();

        if (method_exists($repo, 'resetVariants')) {
            if (null == $relatedIds) {
                $relatedIds = $entity->getRelatedEntityIds();
            }

            if (!in_array($entity->getId(), $relatedIds)) {
                $relatedIds[] = $entity->getId();
            }

            if (null === $variantStartDate) {
                $variantStartDate = new \DateTime();
            }

            // Ensure UTC since we're saving directly to the DB
            $variantStartDate->setTimezone(new \DateTimeZone('UTC'));
            $repo->resetVariants($relatedIds, $variantStartDate->format('Y-m-d H:i:s'));
        }
    }
}