callDepth.bash

# Adjacent function depth.
# Search up the stack for the first non-FUNCNAME[1] and count how deep we are.
# Result goes to stdout, or is optionally assigned to the given variable name.
function callDepth {
	if [[ $FUNCNAME == "${FUNCNAME[1]}" ]]; then
		unset -v n
		printf "$@"
	else
		# If callee is empty then we're definitely being called from global scope.
		# If there is exactly one callee named main, and len(BASH_SOURCE) == 2, then this is also definitely global scope.
		if [[ -z ${FUNCNAME[1]} || ( ${FUNCNAME[-1]} == main && ( ${#FUNCNAME[@]} -eq 2 && ${#BASH_SOURCE[@]} -eq 2 ) ) ]]; then
			typeset n=0
		else
			typeset -i n=1
			while [[ ${FUNCNAME[1]} == "${FUNCNAME[n+1]}" && ${BASH_SOURCE[1]} == "${BASH_SOURCE[n+2]}" ]]; do
				(( n++ ))
			done
		fi
		${1:+"$FUNCNAME" -v} "${1:-printf}" %d "$n"
	fi
}

# Set local options
function localopt {
	typeset -a unsetopts setopts
	typeset opt depth

	if [[ $1 == -n ]]; then
	#	if [[ $2 != +([[:digit:]]) || callDepth depth ]]
	#	then :
	#	fi
	:
	fi

	typeset -f +t "${FUNCNAME[@]::2}"

	for opt; do
		case $opt in
			+*)
				unsetopts+=("${opt#-}")
				set +o "$opt"
				;;
			*)
				setopts+=("$opt")
				set -o "$opt"
		esac

		if [[ $SHELLOPTS != *${opt}* ]]; then
			set -o "$opt"
			unsetopts+=("$opt")
		fi
	done
}

typeset -ft localopt

{ eval function\ {f,main,source}" $(</dev/fd/0) ;"; } <<\EOF
{
	local depth=
	if callDepth depth && (( depth < $1 )); then
		printf '%-2d' "$depth"
		"$FUNCNAME" "$1"
		printf '%-2d' "$depth"
	fi
}
EOF

g() {
	local depth=$(callDepth)
	if (( depth < $1 )); then
		printf '%-2d' "$depth"
		"$FUNCNAME" "$1"
		printf '%-2d' "$depth"
	else
		f 10
	fi
} 

f 10; echo
main 10; echo
callDepth; echo
typeset -xf callDepth f g main
bash -c 'f 10; echo; main 10; echo; g 10; echo; callDepth; echo'
g 10