Zsh collect args

foo.zsh

# Collect args

# -- traditional, piped|, <redirected
function collect_args {
  local data args=()
  if [[ ! -t 0 ]]; then
    while IFS= read -r data || [[ -n "$data" ]]; do
      args+=("$data")
    done
  fi
  printf '%s\n' "$@[@]" "$args[@]"
}

function foo {
  set -- "${(f@)$(collect_args "$@")}"
  local arg
  for arg in "$@"; do
    echo "arg: '$arg'"
  done
}
arr=(1 2 "" 4)
printf "%s\n" "$arr[@]" | foo x "" y z