Protect against dropped databases

[kegsay]

See #448

[devonh]

Changes look good. The comment is much appreciated, especially for future people trying to understand this code.

Would it be simple enough to add a test for this? I imagine something around here would be easiest:

sliding-sync/tests-integration/extensions_test.go

Line 273 in 5da6865

func TestExtensionToDevice(t *testing.T) {

All that should be necessary is to start up a fresh test, add some to-device messages, and do a sync with a position > 0. Then check you received all the messages. That should mimic the DB dropping sequence, without having to go through actually doing that in a test.

[devonh]

New test looks good! (other than the token comparison)