TYPO3 Core

Problem reproduced and located within a "faulty" extension providing an eID script.

Initialization of the TSFE:

    /**
     * Initializes TSFE and sets $GLOBALS['TSFE'].
     *
     * @return void
     */
    protected function initTSFE() {
        $GLOBALS['TSFE'] = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(
            'TYPO3\\CMS\\Frontend\Controller\\TypoScriptFrontendController',
            $GLOBALS['TYPO3_CONF_VARS'],
            \TYPO3\CMS\Core\Utility\GeneralUtility::_GP('id'),
            ''
        );
        $GLOBALS['TSFE']->initFEuser();
        $GLOBALS['TSFE']->checkAlternativeIdMethods();
        $GLOBALS['TSFE']->determineId();
        $GLOBALS['TSFE']->initTemplate();
        $GLOBALS['TSFE']->getConfigArray();

        // Get linkVars, absRefPrefix, etc
        \TYPO3\CMS\Frontend\Page\PageGenerator::pagegenInit();
    }

Warning is triggered with ->determineId() since $GLOBALS['TCA'] is not set.

Problem may be solved by calling an internal bootstrap method, typically after the call to ->initFEuser() (to use same ordering as in bootstrap):

$GLOBALS['TSFE']->initFEuser();
\TYPO3\CMS\Core\Core\Bootstrap::getInstance()->loadCachedTca();
$GLOBALS['TSFE']->checkAlternativeIdMethods();
$GLOBALS['TSFE']->determineId();
$GLOBALS['TSFE']->initTemplate();
...

BEWARE: This only happens ONCE when eID script is called RIGHT AFTER FLUSHING the frontend cache

Indeed, thanks for pointing out.