I just opened this PR for typing, documenting, and refactoring the Sync class (and a bit of CachingLayer):
It took me a few days to get through this, but it’s looking so much better now! 
Most of the types that were still missing are part of this pull request, and the Sync tests have been ported entirely.
I know it’s a lot to ask from a reviewer, but any and all help with getting this merged would be very much appreciated! 
raucao
2
This widget PR uses the new “sync-started” event:
And this one makes it feel snappier simply by removing words from the UI:
