snapcraft.yaml requires the version key, which is often redundant. Plugins will often know the version number (such as encoded in Python setup.py files), but that is just for a single part. Perhaps the version should optionally accept a part name instead of a version number, causing the version number of the part as reported by the plugin to be used for the snap (or an error raised if the plugin does not support it). The main use case would be have snap version numbers matching upstream for automatic builds, such as done by Launchpad. name: juju-deployer summary: Juju deployment lifecycle management description: Juju deployment lifecycle management version: juju-deployer apps:     juju-deployer:         command: juju-deployer parts:     juju-deployer:         plugin: python3         source: lp:juju-deployer