Latest commit 1fa258c
Jan 13, 2017
Optional interfaces are becoming more important in rclone, --track-renames and --backup-dir both rely on them. Up to this point rclone has used interface upgrades to define optional behaviour on Fs objects. However when one Fs object wraps another it is very difficult for this scheme to work accurately. rclone has relied on specific error messages being returned when the interface isn't supported - this is unsatisfactory because it means you have to call the interface to see whether it is supported. This change enables accurate detection of optional interfaces by use of a Features struct as returned by an obligatory Fs.Features() method. The Features struct contains flags and function pointers which can be tested against nil to see whether they can be used. As a result crypt and hubic can accurately reflect the capabilities of the underlying Fs they are wrapping.