asdf shell for asdf 0.16.0+

asdf_shell.zsh

asdf_shell() {
    export "ASDF_${1:u}_VERSION"="$2"
}

# and completion for zsh assuming ASDF_DATA_DIR is set
_asdf_shell_1() {
    local -a plugins=( "${ASDF_DATA_DIR:?}/plugins"/*(:t) )
    compadd -a plugins
}
_asdf_shell_2() {
    local -a versions=( "${ASDF_DATA_DIR:?}/installs/$1"/*(:t) )
    versions+=system
    compadd -a versions
}
_asdf_shell() {
    compset -n 1
    _arguments '1:plugin-name:_asdf_shell_1' '2:tool-version:{_asdf_shell_2 ${words[2]}}'
}
compdef _asdf_shell asdf_shell