lncli: allow openchannel to accept a node's URI

[jamesob]

Many websites (recksplorer, lightninggem) advertise their node in terms of URI.
Allow lncli openchannel to accept a URI (pubkey@host:port) without throwing a
decode error, and use the hostname information to attempt a connection without
having to specify --connect.

This removes --connect as it is no longer needed.

Example usage

 $ lncli openchannel --sat_per_byte 13 02ad6fb8d693dc1e4569bcedefadf5f72a931ae027dc0f0c544b34c1c6f3b9a02b@167.99.50.31:9735 6000000 0

{
        "funding_txid": "d780dd9ff1adc76dfa2f32d05e22d2101c448296b8741262a398c2e3xxxxx"
}

[wpaulino]

Thanks for the PR! I think a better approach would be to just provide either a node pubkey or a URI without the need for a connect flag. If we detect a URI, then we can attempt to connect to it before attempting to open the channel. Thoughts?

[jamesob]

@wpaulino Thanks for the look. Removing --connect sounds fine with me and I'm happy to do so, but I'm wondering how sensitive lncli is to maintaining backwards compatibility. Do we want to first deprecate this flag and then remove it in a subsequent release, or are we okay with an unceremonious removal?

[wpaulino]

I'm on board with removing it, it's a CLI flag so it would only impact those workflows. We usually recommend people to stay pinned to the latest tagged release if they're looking for stability anyway. Will leave the decision to the rest of the team.

[jamesob]

I've pushed changes removing --connect (in lieu of URI use) as suggested by @wpaulino.

[halseth]

nit: I believe req.NodePubkey can be used here directly.

[jamesob]

I don't think so given that the first arg (like node_key above) can either be a pubkey or a URI, and in the latter case we need to unpack it, but maybe I'm missing something.

[halseth]

to clarify, what I meant was the following 😄 Not sure if it works?

	switch {
	case ctx.IsSet("node_key"):
		req.NodePubkey, connectVal, err = decodeNodePubkeyOrURI(
			ctx.String("node_key"))

	case args.Present():
		req.NodePubkey, connectVal, err = decodeNodePubkeyOrURI(
			args.First())
		args = args.Tail()
	default:
		return fmt.Errorf("node id argument missing")
	}

[halseth]

looks like nodeKey is never set in the case where no URI is given?

[jamesob]

D'oh! Good find. Willfix.

[halseth]

I'm in favour of removing --connect 👍

[jamesob]

Pushed changes incorporating @halseth's feedback.

[jamesob]

Tested with both URI and pubkey on mainnet:

$ lncli openchannel --sat_per_byte 40 024a2e265cd66066b78a788ae615acdc84b5b0dec9efac36d7ac87513015eaf6ed@lnd.bitrefill.com 9000000 0

{
        "funding_txid": "3fb66e74b8ece13eebf883d9d210adacc9390bcdd446c580bde59ffc80ab342d"
}

$ lncli openchannel --sat_per_byte 40 03e50492eab4107a773141bb419e107bda3de3d55652e6e1a41225f06a0bbf2d56 2000000 0

{
        "funding_txid": "eb7a1c1d7719131e1756b552564886355cbb83ae749afb7a98fc866cbc6608ed"
}

[Roasbeef]

Needs a rebase!