Set DevEUI from userFields for data packet

[emanuele-dedonatis]

DevEUI is set from userFields only for join requests

[anthonykirby]

Hi @emanuele-dedonatis, thank you for the PR.

I'm puzzled about the use-case for the change: (Please be patient with me, as I can't remember all the details of the LoRA spec!)

As I understand it, DevEUI is used for a "join-request", and there's code to handle it already in _initialiseJoinRequestPacketFromFields (see LoraPacket.ts#L351-L362). This is called if the type is MType.JOIN_REQUEST or if all three of AppEUI, DevEUI & DevNonce are supplied.

However, the PR is passing in a DevEUI when creating a data packet, which I don't understand.

[emanuele-dedonatis]

Hi @anthonykirby, you are right: the DevEUI is not used to build the packet in case mtype is not a JOIN_REQ.

But in my use case, I have a shared function to extract lora-packet info for every mtype. Thus, when it's not a JOIN_REQ, packet.DevEUI will be undefined even if I passed it at initialization time :(

[anthonykirby]

Sorry, I don't understand. If the packet is a JOIN_REQ then you wouldn't expect it to have a DevEUI. (It won't have an AppEUI or DevNonce either, but the PR isn't adding them as well 😁)

I'm concerned that if we allow properties that aren't valid for the current packet type, it would cause confusion for users. We currently allow only valid properties, and I think the validation is useful.

(Of course, it would have been possible to have all packet types allowing all properties - but that's an architecture decision that too late to change.)