_prettier

#!/usr/bin/env bash
# NOTE: prettier allows opts after args (except after `--`)
# TODO: handle redirection and/or use bash-completion pkg
# shellcheck enable=all
# shellcheck disable=SC2250

_prettier() {
    command -v prettier >/dev/null 2>&1 || return

    # shellcheck disable=SC2064
    trap "trap RETURN
        unset -v LC_ALL
        ${LC_ALL+"$(declare -p LC_ALL)"}
        $(shopt -po)
        $(shopt -p)
    " RETURN

    set -fu
    local IFS
    IFS=$' \t\n'
    export LC_ALL=C
    COMPREPLY=()

    local out
    out="$(
        command prettier --help \
            | command sed -n -E \
                -e '/^[[:space:]]*[Uu][Ss][Aa][Gg][Ee]/,/^[[:space:]]*$/b' \
                -e 's/^(([[:space:]]*,?-[^[:space:]]+)+[[:space:]]*(<[^>]+>)?).*/\1/p'
    )"

    local prevword="$3"
    local currword="$2"
    local ifs1=$' \t\n,'
    local ifs2=$' \t\n|>'
    local -a allowed_args
    allowed_args=('[file/dir/glob ...]')

    local -a opts optarr optargarr optargs
    local ln=
    opts=()
    optarr=()
    optargarr=()
    optargs=()

    while read -r ln; do
        IFS="$ifs1"
        optarr=(${ln%%'<'*})
        IFS="$ifs2"
        ln="${ln#*'<'}"
        optargarr=(${ln%'>'*})
        IFS=$' \t\n'
        local opt=

        for opt in "${optarr[@]}"; do
            opts+=("$opt")

            if [ "X$prevword" = "X$opt" ]; then
                optargs=("${optargarr[@]}")
            fi
        done
    done <<<"$out"

    # Short-circuit if cmdline contains '--' before cursor word
    local i=0

    while [ "$i" -lt "$COMP_CWORD" ]; do
        case "${COMP_WORDS[i]}" in
            --)
                return 0
                ;;
        esac

        ((i++))
    done

    # Check if expecting optarg
    case "${optargs[*]}" in
        [Pp][Aa][Tt][Hh]) : ;;

        [Ff][Ll][Aa][Gg])
            local -a flags
            flags=()

            for opt in "${opts[@]}"; do
                opt="${opt#-}"
                flags+=("${opt#-}")
            done

            COMPREPLY+=($(builtin compgen -W '"${flags[@]}"' -- "$currword"))
            unset -v flags
            ;;

        *[![:space:]]*)
            COMPREPLY+=($(builtin compgen -W '"${optargs[@]}"' -- "$currword"))
            ;;

        # No possible optargs for the previous word
        *)
            COMPREPLY+=($(builtin compgen -W '"${opts[@]}"' -- "$currword"))
            [ -z "$currword" ] && COMPREPLY+=("${allowed_args[@]}")
            ;;
    esac
}

builtin complete -o bashdefault -o default -F _prettier prettier