Calling an API method before any packets have arrives results in an exception

[sdwilsh]

It used to be the case that we could call something like synchronize_time() immediately, and everything was okay. However, that no longer is the case with the addition of ECM support:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/src/brultech_serial2mqtt/brultech_serial2mqtt/__main__.py", line 9, in <module>
    loop.run_until_complete(bs2m.start())
  File "/usr/lib/python3.11/asyncio/base_events.py", line 653, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/src/brultech_serial2mqtt/brultech_serial2mqtt/__init__.py", line 54, in start
    await self._setup_gem(device_connection)
  File "/src/brultech_serial2mqtt/brultech_serial2mqtt/__init__.py", line 119, in _setup_gem
    await connection.synchronize_time()
  File "/usr/local/lib/python3.11/dist-packages/aiobrultech_serial/__init__.py", line 127, in synchronize_time
    success = await api.synchronize_time(self._protocol)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/siobrultech_protocols/gem/api.py", line 213, in synchronize_time
    return await set_date_and_time(protocol, time, serial_number, timeout)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/siobrultech_protocols/gem/api.py", line 163, in set_date_and_time
    async with call_api(SET_DATE_AND_TIME, protocol, serial_number, timeout) as f:
  File "/usr/lib/python3.11/contextlib.py", line 204, in __aenter__
    return await anext(self.gen)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/siobrultech_protocols/gem/api.py", line 38, in call_api
    delay = protocol.begin_api_request()
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/siobrultech_protocols/gem/protocol.py", line 449, in begin_api_request
    if self.api_type == ApiType.GEM and self.send_packet_delay:
       ^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/dist-packages/siobrultech_protocols/gem/protocol.py", line 388, in api_type
    assert result

I don't see a great way to fix this, so I'm going to work-around it, but I wanted to file the issue in case @jkeljo had any ideas.

[jkeljo]

Yeah, tricky. If you know what you're connecting to you can pre-configure the protocol for that API type.

I played around just now with sending an ECM API request to my GEM (ignored; client eventually timed out), and sending a GEM API request to my ECM (that mostly also just ignores it until the client times out, though one time I did see the client get confused and try to parse an incoming binary packet as utf-8). So that's not ideal, but I could imagine writing a detection routine based on the idea that a real API response comes in very quickly (like a timeout of 200ms would likely be plenty). It would probably get it wrong (and decide that it is neither a GEM nor an ECM) every once in a blue moon when the system's under load or something and it isn't able to process the response in time, but that's not too big a deal because you can just fall back to waiting for the first packet to figure it out.

[jkeljo]

We should probably raise an actual exception here rather than assert, just so that it's clearer what is going on.

[sdwilsh]

We should probably raise an actual exception here rather than assert, just so that it's clearer what is going on.

Yeah, it took me a bit to figure out what went wrong. I'm going to work around this and just require it to be set in the config for brultech-serial2mqtt at least.