Incident: app launched despite failed migrations

[a-type]

Somehow, on a random chromebook, I was able to launch an app starting from nothing, initialize from server, but fail to migrate. Since the server data was older (version 2) than the codebase (version 3), this left version 3 unapplied. But since the app issued operations with version 3 timestamps, other peers assumed incoming data was pre migrated and did not apply migrations, either.

Pruning made the app still usable, but due to #412 , the pruned data was POJOs instead of entities (it was a new object field with a default value), so the app logic broke. #412 will fix this contingency case, but not the root cause.

Unfortunately I didn't get a good look at the logs for the device I was using when this happened, but I remember seeing "no migration found for version 0" which could be a hint. It's worth testing the case when migration throws an error, to make sure the app does not launch.

[a-type]

Worth noting, to hotfix this in the wild, I think another schema migration deployment which manually migrates the offending collections will work to resolve the problem.

[a-type]

Perhaps this happens if the imported data is empty? So the detected imported max version is undefined, or 0? But that should be a no-op migration according to current pathfinding.