Core

At the moment it does not seem possible to disable the default MediaWizardProvider

TYPO3\CMS\Frontend\MediaWizard\MediaWizardProvider

This also makes it impossible to use custom renderers in TYPO3\CMS\Frontend\ContentObject\MediaContentObject for all URLs that this renderer can handle.

I already tried to extend the MediaWizardProvider with the configuration in

$GLOBALS['TYPO3_CONF_VARS']['SYS']['Objects']['TYPO3\\CMS\\Frontend\\MediaWizard\\MediaWizardProvider']

This does not work because:

1. when I put it in the ext_localconf.php file of my extension (mediaoembed) the configuration file of the cms extension that registers the MediaWizardProvider gets always loaded before the configuration file of the extension, so it does not know about the overwritten class.
2. when I put it my global AdditionalConfiguration.php the overwritten class configuration gets recognized but the class loader will throw an exception because the mediaoembed extension is not loaded (yet).

As far as I can see, there are several approaches to solve this.

1. Do not call \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance() when calling \TYPO3\CMS\Frontend\MediaWizard\MediaWizardProviderManager::registerMediaWizardProvider(). This is just too early. There needs to be some initialization method in the MediaWizardProviderManager that gets called one time at the beginning of getValidMediaWizardProvider(). This would make sure that the class overwriting system is fully initialized.
2. Add a configuration variable for LocalConfiguration.php to disable the registration of the default MediaWizardProvider

Maybe even both solutions should be implemented.

Do you have any input on this? Otherwise I will start writing a patch.

Would this be a bugfix or a feature?