This is a child issue of [#2982674] Problem/Motivation Given a normalization to Composer-based site building, we need a tool to convert non-Composer-based sites into Composer-based ones. We're targeting 'tarball' style installs, which have downloaded Drupal from the download page of drupal.org, and have then installed in place. We want a core-native tool which can be easily used to reliably make a composer.json file, ideally without much user intervention. Proposed resolution

Have BackdropCMS consider making core and contrib modules available in https://packagist.org/? I guess the answer is yes - backdrop-ops/backdropcms.org#8 (comment) But there are any issues/reasons ...