This is needed to properly handle asyncio timeouts. If the future is already done, then set_exception will raise an exception and the self.bus._finalize call will not be reached.
I ran into this failure mode when wrapping bus.call in asyncio.wait_for:
await asyncio.wait_for(bus.call(...), timeout=10)
If the timeout was reached, it would cause an infinite loop of errors:
Traceback (most recent call last):
File "asyncio/events.py", line 127, in _run
File "site-packages/dbus_next/aio/message_bus.py", line 63, in write_callback
asyncio.base_futures.InvalidStateError: invalid state
2020-11-25 12:05:01,578 - asyncio - ERROR - Exception in callback _MessageWriter.write_callback()
handle: <Handle _MessageWriter.write_callback()>
Traceback (most recent call last):
File "site-packages/dbus_next/aio/message_bus.py", line 51, in write_callback
BrokenPipeError: [Errno 32] Broken pipe
During handling of the above exception, another exception occurred:
...
acrisci
commented
3 years ago
This is needed to properly handle asyncio timeouts. If the future is already done, then set_exception will raise an exception and the
self.bus._finalizecall will not be reached.I ran into this failure mode when wrapping
bus.callinasyncio.wait_for:await asyncio.wait_for(bus.call(...), timeout=10)If the timeout was reached, it would cause an infinite loop of errors: