If I change
$library = $this->libraryDiscovery->getLibraryByName('core', 'ckeditor');
to
$library = $this->libraryDiscovery->getLibraryByName('ckeditor', 'ckeditor');
then it gets back a valid return
Array ( [remote] => https://github.com/ckeditor/ckeditor4 [version] => 4.18.0 [license] => Array ( [name] => GNU-GPL-2.0-or-later [url] => https://raw.githubusercontent.com/ckeditor/ckeditor4/4.18.0/LICENSE.md [gpl-compatible] => 1 ) [js] => Array ( [0] => Array ( [preprocess] => [minified] => 1 [group] => -100 [type] => file [data] => modules/contrib/ckeditor/vendor/ckeditor.js [version] => 4.18.0 ) ) [dependencies] => Array ( ) [css] => Array ( ) ) Array ( [remote] => https://github.com/ckeditor/ckeditor4 [version] => 4.18.0 [license] => Array ( [name] => GNU-GPL-2.0-or-later [url] =>
This appears to happen when you are using a contrib ckeditor4 module that is not from core.
Aaronwa → created an issue.