Wikibase requires "data-values/value-view" in its composer.json. That has "type": "mediawiki-extension" in its composer.json, which makes composer install it under extensions instead of vendor, which won't be supported for production and only works for now because it is contained within the Wikidata build. Either change it to be a normal lib/component, which itself is e.g. not allowed to register hooks, the requiring code could to that however. Or (not preferred) stop depending on it via composer, see https://www.mediawiki.org/wiki/Requests_for_comment/Improving_extension_management#Dependencies_upon_extensions .