PubSub and Meshtastic Callback issues

I don’t know why, but you cannot use a closure for callbacks when subscribing to Meshtastic events. It took me days to figure out. Also, the parameter name in pubsub callbacks really matter. Even for positional arguments.

closures are broken

Update: seems to be an issue in pypubsub.

This doesn’t work:

import meshtastic
from pubsub import pub

class Foo:
    def start(self):
        def _on_recv(packet, interface):
            pass # body here to do something with packet

        pub.subscribe(_on_recv, "meshtastic.receive")
        self.interface = meshtastic.serial_interface.SerialInterface("/dev/ttyACM0")

Or more precisely, it will work right up until it exits from the start method. Then, mysteriously, it will no longer work.

Instead, it needs to be more like this:

import meshtastic
from pubsub import pub

class Foo:
    def on_recv(self, packet, interface):
        pass # body here to do something with the packet

    def start(self):
        pub.subscribe(self.on_recv, "meshtastic.receive")
        self.interface = meshtastic.serial_interface.SerialInterface("/dev/ttyACM0")

names matter

Another head-scratcher: when subscribing to “meshtastic.connection.established” you MUST name the arguments exactly.

This works:

    def on_connect(self, interface, topic=pub.AUTO_TOPIC):
        pass # do something here

But this does not work:

    def on_connect(self, iface, topic=pub.AUTO_TOPIC):
        pass # do something here

And the exception is weird:

ERROR:root:Unexpected error in deferred execution 
Traceback (most recent call last):
  File "/nix/store/lz6fkq96sgg6xv9gb6a0wjv446mhnkm1-python3.11-meshtastic-2.3.4/lib/python3.11/site-packages/meshtastic/util.py", line 244, in _run
    o()
  File "/nix/store/lz6fkq96sgg6xv9gb6a0wjv446mhnkm1-python3.11-meshtastic-2.3.4/lib/python3.11/site-packages/meshtastic/mesh_interface.py", line 650, in 
    lambda: pub.sendMessage(
            ^^^^^^^^^^^^^^^^
  File "/nix/store/rhzqg6ih8wmmh6sfpk43vbxw050gbscz-python3.11-pypubsub-4.0.3/lib/python3.11/site-packages/pubsub/core/publisher.py", line 216, in sendMessage
    topicObj.publish(**msgData)
  File "/nix/store/rhzqg6ih8wmmh6sfpk43vbxw050gbscz-python3.11-pypubsub-4.0.3/lib/python3.11/site-packages/pubsub/core/topicobj.py", line 433, in publish
    self._getListenerSpec().check(msgData)
  File "/nix/store/rhzqg6ih8wmmh6sfpk43vbxw050gbscz-python3.11-pypubsub-4.0.3/lib/python3.11/site-packages/pubsub/core/topicargspec.py", line 222, in check
    raise SenderMissingReqdMsgDataError(
pubsub.core.topicargspec.SenderMissingReqdMsgDataError: Some required args missing in call to sendMessage('meshtastic.connection.established', interface): iface

Tags: python, index, meshtastic

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