Some advanced variable manipulation investigation

variables_test.sh

#!/bin/bash

printarr() {
    echo "$msg"
    local x
    for x in "$@"; do
        echo "    $x"
    done
}

add-a() {
    #By using `-n` we can access variables from any context
    #we can essentially reach out by name - perhaps no need for context sourcing
    local -n myarr="$1"

    myarr+=(a)
}

change-s() {
    # even works on strings
    local -n mystr="$1"
    mystr=newvalue
}

func() {
    local f # if 'f' is changed by change-s before func is called, `local` or `declare` will cancel out the change
    echo "  f :: $f"
}

ro () {
    readonly ro_mesg=hello
    echo "  ro >> $ro_mesg"
}

arrdef() {
    local basearr=(one two)

    msg=before/basearr printarr "${basearr[@]}"
    add-a basearr
    msg=after/basearr printarr "${basearr[@]}"

    add-a mainarr
    msg=after/mainarr printarr "${mainarr[@]}"

    thisstr=oldvalue
    echo "thisstr/before :: $thisstr"
    change-s thisstr
    echo "thisstr/after :: $thisstr"

    # Change a "local" before it is called
    change-s f
    func

    echo "Pre-ro"
    change-s ro_mesg
    ro
    echo "Post-ro change-s"
    change-s ro_mesg # bails here
    echo "Post-ro ro"
    ro
    echo "Post re-ro"

}

main() {
    mainarr=(alice bob)
    arrdef

    msg="main/basearr" printarr "${basearr[@]}"
    msg="main/mainarr" printarr "${mainarr[@]}"
}

main "$@"

msg=global/basearr printarr "${basearr[@]}"

Output from above script

before/basearr
    one
    two
after/basearr
    one
    two
    a
after/mainarr
    alice
    bob
    a
thisstr/before :: oldvalue
thisstr/after :: newvalue
  f :: 
Pre-ro
  ro >> hello
Post-ro change-s
variables_test.sh: line 21: ro_mesg: readonly variable
global/basearr