TYPO3 Core

Parent bug was present in Frontend, not in Backend.

Problem located in my case in an Extbase extension because Extbase relies as standard Frontend rendering on config.language_alt to define an alternative language key.

We first have to revert #39220 I'd say because fall back mechanism introduced in 4.6 does not work anymore, it always falls back to English (= source).

By reverting though, we have the bug again in Frontend that a missing translation results in blank output, seems even when using config.language_alt (at least with Extbase).

But then, this config.language_alt is not an option because by reverting the patch, we are forced to set this to "en" in order to tackle with partially translated languages.

BTW, this does not seem to work with Extbase which seems not to properly fall back to the other language.

TYPO3 4.6 introduced a multiple-level fallback which cannot be handled by config.language_alt. I would expect the standard fallback mechanism introduced by TYPO3 4.6 to be automatically taken into account. The question is how? Because then config.alt_language does not make sense anymore.

Tested this with a user-defined language, namely de_AT which should automatically fall back to "de" according to documentation :) Then add a partially translated file and you're done!

User-defined language is described for instance here: http://xavier.perseguers.ch/en/tutorials/typo3/articles/managing-localization-files.html#c954

Please do not test anything here with Extbase. Current implementation of translation in extbase is plain wrong.
If 4.6+ alternative language does not work at all, and fallback to default language doesn't work either.

[1] changes the translation handling in extbase to be the same as in core.

[1] https://review.typo3.org/13039

Patch set 1 for branch TYPO3_4-7 has been pushed to the review server.
It is available at http://review.typo3.org/13801

Patch set 1 for branch TYPO3_4-6 has been pushed to the review server.
It is available at http://review.typo3.org/13802

By the way: pibase getLL also does not handle alternative fallback correctly!!

Patch set 2 for branch master has been pushed to the review server.
It is available at http://review.typo3.org/13800