nil messages are not translated

[Zambito1]

Observed behavior

If you run nats sub with --translate and receive an empty message, the empty message is not piped to --translate. For example:

nats sub foo --translate='wc -c'

And then

nats pub foo bar
nats pub foo ''

will yield

07:21:35 Subscribing on foo 
[#1] Received on "foo"
3

[#2] Received on "foo"
nil body

Expected behavior

nats sub with --translate='wc -c' should yield 0 when receiving an empty message.

Server and client version

cli: v0.1.2-0.20250122082047-856d2dcf4340
server: 2.10.22

Host environment

Client host: GNU Guix

Steps to reproduce

• nats sub foo --translace='wc -c'
• nats pub foo ''
• observe nil body rather than 0

[ripienaar]

hmm, not sure we can safely assume all translators will handle nil inputs?

[Zambito1]

Right now error exit codes are reported when using --translate and the translator fails.

nats sub foo --translate='false' --raw 2>/dev/null

nats pub foo bar

output of the sub:

""
Error while translating msg body: exit status 1

This seems to me like reasonable behavior when running --translate with a translator fails on nil input.

[ripienaar]

OK, we'll fix that

[ripienaar]

@Zambito1 we took a stab at this, do you want to see how main works for you now?

[Zambito1]

@ripienaar main works for me now, thanks!