How to create a sys_file_reference inside another sys_file_reference?

Question

I need to add some track files to a TYPO3 file reference. So I extended the TCA for sys_file_reference and added some fields. One of the fields should be a reference to another file. It works as far that I can chose a file in the backend

Unfortunately, I can't save if I have a track added. TYPO3 throws me an exception.

#1300098528 InvalidArgumentException Incorrect reference to original file given for FileReference.

This exceptions happens because uid_local of the track reference is 0. But I don't know why this is 0 and how to fix it.

This is my TCA Configuration

'tx_eos_video_tracks' => [
    'exclude' => 1,
    'label' => 'Track files',
    'description' => 'captions, chapters, descriptions, metadata, subtitles',
    'config' => \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::getFileFieldTCAConfig('tx_eos_video_tracks', [
        'appearance' => [
            'createNewRelationLinkTitle' => 'Add Track'
        ],
        'overrideChildTca' => [
            'types' => [
                '0' => [
                    'showitem' => '
                    --palette--;;tx_eos_video_tracks_palette'
                ]
            ],
        ],
    ], 'vtt,srt')
],

Answer 1

Ok, I found the Solution. There must be always the fields uid_local, hidden, sys_language_uid, l10n_parent in the Child TCA. There is a predefined palette ('filePalette') which adds the fields without showing them to the user.

So Changing

'overrideChildTca' => [
        'types' => [
            '0' => [
                'showitem' => '
                --palette--;;tx_eos_video_tracks_palette'
            ]
        ],
    ],

to

'overrideChildTca' => [
        'types' => [
            '0' => [
                'showitem' => '
                --palette--;;tx_eos_video_tracks_palette,
                --palette--;;filePalette'
            ]
        ],
    ],

resolves my Issue