New BusState members per #736

[bggardner]

No description provided.

[bggardner]

I also have a change ready that queries the system for the state of a SocketcanBus, but it depends on the pyroute2 package. I didn't want to cause another dependency, but this seemed to be the most efficient way to query the interface state. Should it be a package-wide dependency, or lazily loaded within the class/method?

    @property
    def state(self) -> BusState:
        try:
            with pyroute2.IPRoute() as ipr:
                operstate = ipr.get_links(ipr.link_lookup(ifname=self.channel)[0])[0].get_attr('IFLA_OPERSTATE')
        except:
            return BusState.UNKNOWN # Could be BusState.STOPPED instead (channel doesn't exist)
        if operstate == 'ERROR-ACTIVE':
            return BusState.ERROR_ACTIVE
        elif operstate == 'ERROR-PASSIVE':
            return BusState.ERROR_PASSIVE
        elif operstate == 'BUS-OFF':
            return BusState.BUS_OFF
        elif operstate == 'STOPPED':
            return BusState.STOPPED
        else:
            return BusState.UNKNOWN

[zariiii9003]

Generally i agree with this, but the consequence is, that BusState should not be passed to BusABC.__init__() anymore. That could be replaced with a universal parameter listen_only: bool for all interfaces. The BusABC.state.setter should also be removed and replaced with a BusABC.listen_only property,

It's a breaking change, but we could do this in a 5.0 release. We have to cleanup all the deprecations at some point anyway.
@hardbyte What do you think?

[bggardner]

I'm not sure I follow you since BusState isn't passed to BusABC.__init__(). I agree that BusABC.state.setter should be removed, though I think listen_only: bool is not a direct replacement, but a "feature" of the specific interface. To prevent a breaking change, we could just add the BUS_OFF and UNKNOWN members, then replace them with the more appropriate names in 5.0 (ACTIVE => ERROR_ACTIVE, PASSIVE => ERROR_PASSIVE, ERROR => STOPPED).

[zariiii9003]

state is passed to subclasses of BusABC to enable monitoring mode like here:

python-can/can/interfaces/pcan/pcan.py

Line 124 in 654a02a

state: BusState = BusState.ACTIVE,

It's ugly and should be replaced with listen_only (same name as in socketcan) in my opinion...