Zsh: complete hostnames and files in given directory

Thank you for the interesting question. I would like to do the same in my scripts. The documentation is dense and not so easy to understand; I have not yet learned to work without actual options in the script. Here's my first attempt at accomplishing the goal with actual options.

First, I created a shell script named myscript.sh that uses options.

#!/usr/bin/env sh
self=$(basename "$0")
hflag=0 # Boolean: hflag is not yet detected
dflag=0 # Boolean: dflag is not yet detected

function usage() {
    echo "Usage: $self [ -h <hostname> | -d <directory> ]"
}

# If no options were given, exit with message and code.
if (($# == 0)); then
    usage
    exit 1
fi

# Process options and option arguments.
while getopts ":h:d:" option; do
    case "${option}" in
        h ) hflag=1 # The h option was used.
            host=${OPTARG} # The argument to the h option.
            ;;
        d ) dflag=1 # The d option was used.
            dir=${OPTARG} # The argument to the d option.
            ;;
        \?) # An invalid option was detected.
            usage
            exit 1
            ;;
        : ) # An option was given without an option argument.
            echo "Invalid option: $OPTARG requires an argument" 1>&2
            exit 1
            ;;
    esac
done

# One of hflag or dflag was missing.
if [ $hflag -eq 0 ] || [ $dflag -eq 0 ]; then
    usage
    exit 1
fi

# Do something with $host and $dir.
# This is where the actions of your current script should be placed.
# Here, I am just printing them.
echo "$host"
echo "$dir"

# Unset variables used in the script.
unset self
unset hflag
unset dflag

Next, I determined where zsh looks for autocomplete files.

print -rl -- $fpath

I chose one of the directories, /usr/local/share/zsh/site-functions in my case. The filenames that are considered autocomplete files begin with an underscore _ character. I created the file, _myscript, in the directory. The portion after #compdef is the actual script name, above.

#compdef myscript.sh

_myscript() {
    _arguments '-h[host]:hosts:_hosts' '-d[directory]:directories:_directories'
}

_myscript "$@"

I then executed compinit to pick up the new autocomplete definition provided by the _myscript file. The result is that I can now use tab completion to specify a host after the -h option and a directory after the -d option while still maintaining some sanity in the parsing of options and option arguments in the script itself. The tab completion presents available options even before invoking myscript.sh as well as making option order irrelevant.

Usage becomes something like the following.

myscript.sh -h <TAB> -d ~/test/<TAB>

Summary Solution

On the second attempt, I created a simple shell script, zscript.sh.

#!/usr/bin/env sh
echo "$1"
echo "$2"

And I created a file, /usr/local/share/zsh/site-functions/_zscript.

#compdef zscript.sh

_zscript() {
    _arguments '1: :->hostname' '2: :->directory'
    case $state in
    hostname)
        _hosts
    ;;
    directory)
        _directories -W $HOME/test/
    ;;
    esac
}

I executed compinit.