core-bundle/src/Routing/Matcher/LanguageFilter.php
public function filter(RouteCollection $collection, Request $request): RouteCollection
    {
        $languages = $request->getLanguages();

        foreach ($collection->all() as $name => $route) {
            if ('.fallback' !== substr($name, -9) && ($this->prependLocale || '.root' !== substr($name, -5))) {
                continue;
            }

            /** @var PageModel $pageModel */
            $pageModel = $route->getDefault('pageModel');

            if (
                !$pageModel instanceof PageModel
                || $pageModel->rootIsFallback
                || \in_array($pageModel->rootLanguage, $languages, true)
                || preg_grep('/'.preg_quote($pageModel->rootLanguage, '/').'_[A-Z]{2}/', $languages)
            ) {
                continue;
            }

            $collection->remove($name);
        }

        return $collection;
    }
public function filter(RouteCollection $collection, Request $request): RouteCollection
    {
        $languages = $request->getLanguages();

        foreach ($collection->all() as $name => $route) {
            if ('.fallback' !== substr($name, -9) && ($this->prependLocale || '.root' !== substr($name, -5))) {
                continue;
            }

            /** @var PageModel $pageModel */
            $pageModel = $route->getDefault('pageModel');

            if (
                !$pageModel instanceof PageModel
                || $pageModel->rootIsFallback
                || \in_array($pageModel->rootLanguage, $languages, true)
                || preg_grep('/'.preg_quote($pageModel->rootLanguage, '/').'_[A-Z]{2}/', $languages)
            ) {
                continue;
            }

            $collection->remove($name);
        }

        return $collection;
    }
{@inheritdoc}