shopt_ensure

shopt_ensure.sh

# -*- mode: sh; sh-shell: bash; -*-
# shellcheck shell=bash

# MIT license (c) 2021 https://github.com/slowpeek
# Homepage: https://gist.github.com/slowpeek/3e592af3395cfb0e2d20a57c50a87a4b

# bye.sh https://gist.github.com/slowpeek/6127166369d8abd230c30c20cc6a9152
# stack.sh https://gist.github.com/slowpeek/3310c2f09b80d0b2e175122e8c8cae64

# This is a wrapper around bash builtin shopt. It can be used to save
# the current state for some options, set/unset those and recover the
# original state later.
#
# shopt_ensure is like shopt, it uses -s/-u switches to set/unset
# options. Unlike shopt, it accepts both in a single call:
#
#     shopt_ensure -s opt1 opt2 -u opt3
#
# -s/-u can be mixed any way:
#
#     shopt_ensure -s opt1 opt2 -u opt3 opt4
#     shopt_ensure -s opt1 -s opt2 -u opt3 -u opt4
#     shopt_ensure -u opt1 -s opt2 -u opt3 -s opt4
#
# By default there is implicit -s: 'shopt_ensure opt' is the same as
# 'shopt_ensure -s opt'.
#
# On shopt_ensure call the original state of the options listed as
# args is pushed into a stack as a single element. shopt_ensure_undo
# pops off an element and uses it to restore the saved state.
#
# EXAMPLE
#
# shopt_ensure -s globstar nullglob
# printf '%s\n' **
# shopt_ensure_undo

_ () {
    unset -f _

    declare -g -A SE__NAMES=() # Valid option names.

    local opt
    while read -r opt; do
        SE__NAMES[${opt%%[[:space:]]*}]=t
    done < <(shopt; shopt -o)
}; _

shopt_ensure () {
    local mode=s state

    while (($# > 0)); do
        if [[ $1 == -[su] ]]; then
            mode=${1:1}
            shift
            continue
        fi

        [[ -v SE__NAMES[$1] ]] || bye "Unknown option ${1@Q}"

        if shopt -q "$1"; then
            state+=" s $1"
            [[ $mode == s ]] || shopt -u "$1"
        else
            state+=" u $1"
            [[ $mode == u ]] || shopt -s "$1"
        fi

        shift
    done

    [[ -n ${state-} ]] || bye 'Empty options list.'

    push_n shopt_ensure state
}

shopt_ensure_undo () {
    local state
    pop_n shopt_ensure state

    # shellcheck disable=SC2086
    set -- $state

    while (($# > 0)); do
        shopt -"$1" "$2"
        shift 2
    done
}