Bash empty array expansion with `set -u`

Question

I\'m writing a bash script which has set -u, and I have a problem with empty array expansion: bash appears to treat an empty array as an unset variable during e

Answer 1

@ikegami's accepted answer is subtly wrong! The correct incantation is ${arr[@]+"${arr[@]}"}:

$ countArgs () { echo "$#"; }
$ arr=('')
$ countArgs "${arr[@]:+${arr[@]}}"
0   # WRONG
$ countArgs ${arr[@]+"${arr[@]}"}
1   # RIGHT
$ arr=()
$ countArgs ${arr[@]+"${arr[@]}"}
0   # Let's make sure it still works for the other case...