The offline state in the Spotify client is specific to that single client, and isn’t synced with other computers/devices. For example, you have different sets of offline music on your computer and your phone. Thus, what you set as offline in your Spotify client does in no way affect Mopidy-Spotify.
In the current version of Mopidy-Spotify, there is no support for offline music. I’m working on finishing Mopidy-Spotify 2 this holiday. It will not initially support offline music either, but all the foundations for supporting it is there, and the feature is high on the wish list, ref. Offline Playlists/Albums/Artists · Issue #10 · mopidy/mopidy-spotify · GitHub.
@jodal - really appreciate the run down on Spotify, I have to admit I was introduced through Spotify through Mopidy as I live in a country that doesnt support it yet (Tanzania). But after exploring, the benefits are obvious. But I also happen to live in a place where internet bandwidth is expensive, slow (comparatively) and unreliable. So the idea of haing any locally cached copy of Spotify or even Soundcloud would be amazing.
Keep up the great work and I’ll stay tuned for the new version.
For now, the commits you refer to is mostly about keeping Mopidy-Spotify from crashing in the seconds before the Spotify authentication succeeds and when the network/Spotify service becomes unavailable.
With time, I’d like to add proper offline support. I guess the main blocker is to decide how to mark playlists for offline storage. One old pull request did so by adding a config to list the names/URIs of all playlists you want to have available offline. Personally, I’d like to be able to mark playlists for offline syncing without changing the config and restarting Mopidy. Currently, there’s no APIs in Mopidy we can use for this, so if we’re going down this path, there’s more thinking and designing to do.