What's the equivalent to ${var:-defaultvalue} in fish?

Question

Hello I am trying to translate my .bashrc to fish format almost done, mostly is clear on the documentation but this part is giving me a headache.. is so my gnupg works with

Answer 1

Since ${var:-value} expands to value if $var is empty, you can always replace it by writing your code out the long way:

begin
  if test -n "$gnupg_SSH_AUTH_SOCK_by"
    set result "$gnupg_SSH_AUTH_SOCK_by"
  else
    set result 0
  end

  if [ "$result" -ne %self ]
    set -x SSH_AUTH_SOCK "/run/user/$UID/gnupg/S.gpg-agent.ssh"
  end
  set -e result
end

_{Note that I don't use (a) endorse, (b) condone the use of, or (c) fail to hold unwarranted prejudices against users of, fish. Thus, my advice is very much suspect, and it's likely that there are considerably better ways to do this.}