ext_localconf.php

<?php

$boot = function ($extensionKey) {
    if (class_exists(\ApacheSolrForTypo3\Solr\Search\SearchComponentManager::class)) {
        \ApacheSolrForTypo3\Solr\Search\SearchComponentManager::registerSearchComponent('fluid_grouping', \ApacheSolrForTypo3\Solrfluidgrouping\Search\GroupingComponent::class);
    }


    if (class_exists(\ApacheSolrForTypo3\Solr\Domain\Search\ResultSet\Result\Parser\ResultParserRegistry::class)) {
        /** @var $parserRegistry */
        $parserRegistry = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\ApacheSolrForTypo3\Solr\Domain\Search\ResultSet\Result\Parser\ResultParserRegistry::class);

        if(!$parserRegistry->hasParser(\ApacheSolrForTypo3\Solrfluidgrouping\Domain\Search\ResultSet\Grouping\Parser\GroupedResultParser::class, 200))
        {
            $parserRegistry->registerParser(\ApacheSolrForTypo3\Solrfluidgrouping\Domain\Search\ResultSet\Grouping\Parser\GroupedResultParser::class, 200);
        }
    }
};

$boot($_EXTKEY);
unset($boot);