TYPO3 Core

Same Issue for suggest wizard: #76661
There is already a patch attached. This should be the same in this case. There is a small piece of code missing, which merges the arrays.

I guess someone only has to find the accordingly place, we then could refactor the patch to provide a new method to merge the columnsOverrides and use this new method.

For Content Element Wizard, the default Value can already be added. See: https://docs.typo3.org/typo3cms/TSconfigReference/PageTsconfig/Mod.html#newcontentelement-wizarditems it's mod.wizards.newContentElement.wizardItems.[group].elements.[name].tt_content_defValues.

I'm not sure when default from TCA is applied, is it also applied if one changes the CType? Or is a field unchanged in that case? If so, it doesn't make sense to use default for tt_content depending on type I guess.

The value for the backend form field is set in backend/Classes/Form/Container/SingleFieldContainer

Even if $parameterArray['fieldConf']['config']['default'] contains the correct value (including columnsOverrides), the defined default value for the fields comes from $this->data['databaseRow'][$fieldName]. But this data depends on the processing within backend/Classes/Form/FormDataProvider
which a defined in ['formEngine']['formDataGroup']['tcaDatabaseRecord'] within the DefaultConfiguration

"DatabaseRowDefaultValues" sets the value. But the issue here is, that the "TcaColumnsOverrides" comes after "DatabaseRowDefaultValues".
I've tried simply changing the dependency, so that "DatabaseRowDefaultValues" depends on "TcaColumnsOverrides", but it didn't worked out. I run into a dependency cycle exception.

I currently have no clue how to resolve this dependency hell. :-/

Push...
Have the same problem but no solutions :-(

It looks like the dependencies of the dataproviders are a bit messed up here.

I solved it by adding my own dataprovider at the end of the list which puts again the default value from processedTCa into the databaseRow default values (tested only in TYPO3 8.7 yet)

DatabaseRecordSetColumnDefaultValue.php:

namespace Ruhmesmeile\RmCustomElements\DataProviders;

use TYPO3\CMS\Backend\Form\FormDataProviderInterface;

class DatabaseRecordSetColumnDefaultValue implements FormDataProviderInterface
{
    public function addData(array $result)
    {

        foreach ($result['processedTca']['columns'] as $columnName => $column) {

            $default = $column['config']['default'] ?? null;
            if (!$result['databaseRow'][$columnName] || empty($result['databaseRow'][$columnName])) {
                if ($default) {
                    $result['databaseRow'][$columnName] = [$default];
                }
            }
        }

        return $result;
    }
}

ext_localconf.php:

$GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][\Ruhmesmeile\RmCustomElements\DataProviders\DatabaseRecordSetColumnDefaultValue::class] = [
    'depends' => [
        \TYPO3\CMS\Backend\Form\FormDataProvider\TcaColumnsOverrides::class,
    ]
];

Patch set 1 for branch 9.5 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/64352