TYPO3 Core

Method \TYPO3\CMS\Core\Configuration\ConfigurationManager::writeLocalConfiguration() cleans up $TYPO3_CONF_VARS before writing to typo3conf/LocalConfiguration.php. It uses the cleanup method ArrayUtility::renumberKeysToAvoidLeapsIfKeysAreAllNumeric() which rewrites the indices of numerically indexed arrays.

This cleanup breaks $TYPO3_CONF_VARS['LOG']['writerConfiguration'] because the configuration uses log level constants which represent integers (see class \TYPO3\CMS\Core\Log\LogLevel) as indices.

Either exceptions for those cleanups must be configurable or (better) this optimization attempt should be dropped at all.