zsh completion with nested control functions - autocomplete

Question

I'm writing completion function for zsh. I took cargo completion function as a basis for mine. For the most part it works fine except for -h and --help options. Completion ouput for these functions is unaligned and repeated multiple times (presented below). This only happens when control functions (_describe, _arguments etc) are present in case structure.
Why this is happening and how can I fix this behavior?
Completion function:
#compdef test
_test() {
local context state state_descr line
typeset -A opt_args
_arguments \
"(- 1 *)"{-h,--help}"[Help]" \
"1: :->command" \
"*:: :->args"
case $state in
command)
_alternative 'arguments:custom arg:(a b c)'
;;
args)
_arguments \
"-a[All]" \
"-n[None]"
esac
}
_test
Shell output:
> test -[TAB]
--help
-h
-- Help
--help
-h
-- Help
--help
-h
-- Help

Answer 1

I've just encountered the same issue. The solution is to return zero from your completion function:
#compdef test
_test() {
...
return 0
}
_test
All completion scripts that I've seen use ret variable which is initially 1 and then set to 0 if any completion function succeeded:
#compdef test
_test() {
local context state state_descr line
local ret=1
typeset -A opt_args
_arguments \
"(- 1 *)"{-h,--help}"[Help]" \
"1: :->command" \
"*:: :->args" && ret=0
case $state in
command)
_alternative 'arguments:custom arg:(a b c)' && ret=0
;;
args)
_arguments \
"-a[All]" \
"-n[None]" && ret=0
esac
return ret
}
_test
I'm not sure why they do it, though.