FYI: aCalendar+ does this, using OpenTasks storage backend. (Not open source though.)
Continue syncing calendar after failure
Steps to reproduce:
- Set up a Caldav calendar (mailbox.org here).
- With DAVx5 connect to this calendar.
- Cause an syncing error. In this case deleting a recurrent birthday reminder caused an error 403 (Forbidden) from the server.
- DAVx5 continues with the next sync item, trying to sync as many items as possible.
- DAVx5 informs the user about all failed items.
DAVx5 stops the sync. Many other sync items are not synced because one single failure.