TYPO3 Core

I can confirm the issue and I would like to submit a patch. Instead of getting the fallback chain from the current page and current language, we need to get the fallback chain from the requested page and requested overlay language.

Something along the lines of:

// PageRepository::getPagesOverlay
// …
$overlays = [];
// If language UID is different from zero, do overlay:
if ($languageUid) {
    $siteFinder = GeneralUtility::makeInstance(SiteFinder::class);
    foreach ($pagesInput as $origPage) {
        $pageUid = is_array($origPage) ? (int)($origPage['uid'] ?? 0) : (int)$origPage;
        $site = $siteFinder->getSiteByPageId($pageUid);
        $siteLanguage = $site->getLanguageById($languageUid);
        $languageAspect = LanguageAspectFactory::createFromSiteLanguage($siteLanguage);
        $languageUids = array_merge([$languageUid], $this->getLanguageFallbackChain($languageAspect));
        $additionalOverlays = $this->getPageOverlaysForLanguageUids([$pageUid], $languageUids);
        $overlays = array_merge($overlays, $additionalOverlays);
    }
}

• Unfortunately, the call to `$site->getLanguageById($languageUid)` leads to an endless loop via the RootlineUtility.
• There might be a negative performance impact, as the pages do not get overlaid as bulk, but page by page. It might be more efficient to group the overlay queries by site and target language.

I just realized that this may already have been dealt with in https://forge.typo3.org/issues/98303.

@hannes: Supercurious to see if you have a solution for this problem in v11 (or even 12).

Adding this here for future investigation: https://extensions.typo3.org/extension/mst_contentfallback