compadd failure during optparse-applicative zsh completion script - zsh

Question

So I'm not exactly sure whether this is something wrong with optparse-applicative's script or if I'm using it wrong.
In the optparse-applicative readme, it states that programs are made available with automatic completion scripts, with options for zsh. For my program setup:
$> setup --zsh-completion-script `which setup`
Outputs:
#compdef setup
local request
local completions
local word
local index=$((CURRENT - 1))
request=(--bash-completion-enriched --bash-completion-index $index)
for arg in ${words[#]}; do
request=(${request[#]} --bash-completion-word $arg)
done
IFS=$'\n' completions=($( /Users/anrothan/.local/bin/setup "${request[#]}" ))
for word in $completions; do
local -a parts
# Split the line at a tab if there is one.
IFS=$'\t' parts=($( echo $word ))
if [[ -n $parts[2] ]]; then
if [[ $word[1] == "-" ]]; then
local desc=("$parts[1] ($parts[2])")
compadd -d desc -- $parts[1]
else
local desc=($(print -f "%-019s -- %s" $parts[1] $parts[2]))
compadd -l -d desc -- $parts[1]
fi
else
compadd -f -- $word
fi
done
I'm running the following in my zshrc (I use oh-my-zsh, but I removed it and this still happens in a bare-minimum config with only a small PATH addition to get the setup script).
autoload -U +X compinit && compinit
autoload -U +X bashcompinit && bashcompinit
source <(setup --zsh-completion-script `which setup`)
I get the following error several times:
/dev/fd/11:compadd:24: can only be called from completion function
I've run compinit, and the completion script seems to look right to me, and I've looked around but I can't seem to figure out why this error is happening...

Answer 1

You don't need to source zsh-completion scripts, they just need to be added to your fpath parameter.
So just place the output of setup --zsh-completion-script $(which setup) in a file call _setup in $HOME/.config/zsh/completions.
fpath=($HOME/.config/zsh/completions $fpath)
autoload -U compinit && compinit