This completion script supports custom commands and flags by reading the ace-manifest.json file with jq. In order to use this script, you must install the jq utility (See this).
To install it, you need to download the file _node_ace and put it in folder covered by your fpath.
Since I failed to apply the script to the node ace command, this script applies to the command na.
Unfortunately, aliases like alias na="node ace" breaks the completion, so I added a little function in my .zshrc :
na() {
node ace "$@"
}