Cannot setopt with empty string

[timrprobocom]

While trying to use nngpp with a pub/sub protocol, I spent hours trying to diagnose why I never received anything, while the exact same sequence using nng calls worked. The problem was this:
socket.set_opt( NNG_OPT_SUB_SUBSCRIBE, "" );
The problem is that the type translation results in this becoming:
nng_setopt( socket, NNG_OPT_SUB_SUBSCRIBE, "", 1 );
as a one-byte buffer (containing \0). To succeed, the fourth parameter needs to be 0. This can be force by using
socket.set_opt( NNG_OPT_SUB_SUBSCRIBE, nng:view("",0) );
but that seems to be a hack.

I cannot think of any situations where the zero-terminator should be included in a set_opt string.

[cwzx]

This behaviour is consistent with nng, which by default will include the null terminator when setting string options (see here).

A couple of things that should work:

• Use the generic setter with a default-constructed view: sock.set_opt( NNG_OPT_SUB_SUBSCRIBE, {} )
• Use the string setter with a nullptr: sock.set_opt_string( NNG_OPT_SUB_SUBSCRIBE, nullptr )

[timrprobocom]

Got it, thanks.

[hu553in]

OMG, I was absolutely at a deadlock for a couple of days.
Thank you @cwzx, it's great!

[carlocorradini]

Super helpful! Saved my day! 🤯🤯🤯
This issue should be pinned.
Do you think this should also be added in the docs?