Empty Array as Error Value when using `invoke`

[Athan Clark]

I don't have a reproducible example at this moment, but what would cause this value to be an array, or an empty one?

bus.invoke({
  // ... args
}, function (e, result) {
  // usually e is either `null` or some error, in my case it's the empty array `[]`
});

[Athan Clark]

However, to be clear, result === undefined when e === [] as well, so there must be an error going on under the hood.

[Andrey Sidorov]

code that calls your callback is here: https://github.com/sidorares/node-dbus/blob/d9a8176dea9d02c50b75a46c0cee8bf45e92da86/lib/bus.js#L109

can you dump what's in the message? Depending on message type, the callback is supposed to be called as (null, ...message.body) if it's method return and (...messageBody) if it's 'error'

I guess correct way would be do do something like this for error:

const err = new Error();
err.messageBody = msg.body;
handler(err);

[Athan Clark]

Do you mean the return message? This is what I received:

{ serial: 3,
  signature: '',
  errorName: 'org.freedesktop.DBus.Error.InvalidParameters',
  replySerial: 2,
  destination: ':1.309',
  sender: ':1.311',
  type: 3,
  flags: 0 }

[Athan Clark]

The weird part is I know for sure that the method I'm calling has a String -> String type signature - I can see it with d-feet. I'm trying to find the line where I can inject some logging for the messages I'm sending, if you can point me in the direction :x

[Andrey Sidorov]

Actually what you get is kind of expected, it's just error message body is empty
Probably more important for your logic is error name returned:

bus.invoke({
  // ... args
}, function (e, result) {
  if (e !== null) {
    console.log(this.message.errorName)
  }
});

[Andrey Sidorov]

I'll keep this issue open to track api change: in case of error instance of Error() will be returned with message set to msg.errorName

[Athan Clark]

yeah I think you're right, this makes a ton of sense. I'll close this now that we know where the issue is. Thank you for your help!!