This is part of #1464 and incorporates Rusty's suggested updates from #1569.
See comment in param.h for description, here's the basics:
unsigned cltv;
const jsmntok_t *note;
u64 msatoshi;
struct param * mp;
if (!param_parse(cmd, buffer, tokens,
param_req("cltv", json_tok_number, &cltv),
param_opt("note", json_tok_tok, ¬e),
mp = param_opt("msatoshi", json_tok_u64, &msatoshi),
NULL))
return;
if (param_is_set(mp))
do_something()
There is a lot of developer mode code to make sure we don't make mistakes,
like trying to unmarshal into the same variable twice or adding a required param
after optional.
During testing, I found a bug (of sorts) in the current system. It allows you
to provide two named parameters with the same name without error; e.g.:
# cli/lightning-cli -k newaddr addresstype=p2sh-segwit addresstype=bech32
{
"address": "2N3r6fT65PhfhE1mcMS6TtcdaEurud6M7pA"
}
It just takes the first and ignores the second. The new system reports this as an
error for now. We can always change this later.
