Cannot reobserve a characteristic after canceling a job containing a call to observe

[mmeisel]

I have the same use case as in Q&A answer #592 except that I sometimes need to re-observe the characteristic during the same connection.

Using kable 0.31.1 on Android, I did exactly as the answer suggested, using cancelAndJoin() to cancel a launched job. This does successfully write DISABLE_NOTIFICATION_VALUE to the descriptor. However, when I call observe() on the characteristic again, kable seems to think the characteristic is already being observed, and does not write ENABLE_NOTIFICATION_VALUE.

I've tracked this down (using the debugger) to the fact that didStartObservation is never set to false -- I set a breakpoint at this line, and it is never reached. AFAICT, this is because the cancellation of the job causes the next suspend function, which happens to be BluetoothDeviceAndroidPeripheral.setConfigDescriptor(), to throw a CancellationException on completion, which is propagated back to the previous line in Observation.kt.

[twyatt]

Thanks for the thorough bug report! I'll try to take a look at it soon. PRs are also welcome.

[mmeisel]

Thanks for the quick response @twyatt! I'd be happy to submit a PR if I could figure out the root cause! I was able to work around this issue by using a different un-observation strategy -- takeWhile() { stillObserving } on the returned flow, where stillObserving is a volatile boolean that I just set to false when I want to stop observing. This seems to work fine.