Importing on Windows systems results in an AttributeError

[koenvervloesem]

Describe the bug

Importing the module on Windows systems results in an AttributeError because bluetooth-adapters tries to access D-Bus.

To Reproduce

Run from bluetooth_adapters import get_adapters on Windows.

Minimal example:

import asyncio
from bluetooth_adapters import get_adapters


async def diagnostics():
    bluetooth_adapters = get_adapters()
    await bluetooth_adapters.refresh()
    print(f"Default adapter: {bluetooth_adapters.default_adapter}")


if __name__ == "__main__":
    asyncio.run(diagnostics())

Get a stack trace like this one (from other code than the above):

Traceback (most recent call last):
File "", line 198, in _run_module_as_main
File "", line 88, in _run_code
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\TheengsGateway\diagnose.py", line 157, in
asyncio.run(diagnostics())
File "C:\Program Files\Python311\Lib\asyncio\runners.py", line 190, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "C:\Program Files\Python311\Lib\asyncio\runners.py", line 118, in run
return self.loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Program Files\Python311\Lib\asyncio\base_events.py", line 653, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\TheengsGateway\diagnose.py", line 153, in diagnostics
await adapters()
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\TheengsGateway\diagnose.py", line 129, in adapters
from bluetooth_adapters import get_adapters
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\bluetooth_adapters_init.py", line 12, in
from .dbus import (
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\bluetooth_adapters\dbus.py", line 10, in
from dbus_fast import BusType, Message, MessageType, unpack_variants
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\dbus_fast_init.py", line 1, in
from . import aio, glib, introspection, message_bus, proxy_object, service
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\dbus_fast\aio_init.py", line 1, in
from .message_bus import MessageBus
File "C:\Users\JC\AppData\Roaming\Python\Python311\site-packages\dbus_fast\aio\message_bus.py", line 29, in
from .message_reader import build_message_reader
File "src\dbus_fast\aio\message_reader.py", line 1, in init dbus_fast.aio.message_reader
File "src\dbus_fast_private\unmarshaller.py", line 16, in init dbus_fast._private.unmarshaller
AttributeError: module 'socket' has no attribute 'CMSG_LEN'

Additional context

Removing lines 12-17 from bluetooth_adapters/__init__.py makes the code work on Windows:

from .dbus import (
    BlueZDBusObjects,
    get_bluetooth_adapter_details,
    get_bluetooth_adapters,
    get_dbus_managed_objects,
)

The code should probably only import from the dbus module on Linux?

[bdraco]

This library is mostly used for Home Assistant which only supports WSL.

I don't have a windows machine to test with but I'm happy to merge a fix as long as it doesn't break WSL

[koenvervloesem]

Ok, I'll also test this on macOS and add a check on the operating system for a conditional import. I'll open a PR soon.

[koenvervloesem]

There's no problem on macOS. However, looking at it deeper, it seems the problem on Windows is only because socket.CMSG_LEN isn't defined on Windows and is used in dbus-fast's unmarshaller module.

Wouldn't the cleanest way to fix this be an alternative implementation for UNIX_FDS_CMSG_LENGTH in dbus-fast? I don't know anything about Windows socket programming, though, so I don't know what this value should be.

[bdraco]

There's no problem on macOS. However, looking at it deeper, it seems the problem on Windows is only because socket.CMSG_LEN isn't defined on Windows and is used in dbus-fast's unmarshaller module.

Wouldn't the cleanest way to fix this be an alternative implementation for UNIX_FDS_CMSG_LENGTH in dbus-fast? I don't know anything about Windows socket programming, though, so I don't know what this value should be.

dbus will likely never be installed on windows so ideally its never imported there

[koenvervloesem]

Got it. Fixed and tested on Linux, Windows and macOS.