[TYPO3-dam] Required fields during upload index_fieldList ?

[georg kuehnberger]

Hi all,

There's the standard way of setting dam-fields to required, like
$TCA['tx_dam']['columns']['title']['config']['eval'] = 'required';
which is fine and works as advertized, however only during editing the 
metadata of a given, already uploaded file.

In order to REALLY force the editor to fill-in certain fields (title, 
caption, alt-text in my case), this required check would have to happen 
during upload, and otherwise reject the upload.

Me feels this should be configurable via, eg:
    $TCA['tx_dam']['txdamInterface']['index_fieldList']

However, I dont find any way to make certain fields "required" here.
Am I missing some un/documented feature, or is it currently not possible 
to make fields required during upload (via configuration)?

Thanks upfront, regards georg