Wrapper for making cabal refuse to work outside of sandboxes

cabal-wrapper.sh

#!/bin/sh

# This is a wrapper around cabal which will fail to execute if
# it's not invoked in a sandbox, although this behaviour can be
# worked around (with a warning message) using the command-line
# flag `--trust-me`.

contains_escape() {
	# Find out whether the arguments contain --trust-me
	ARR=$@
	if [[ $ARR = ${ARR[@]//--trust-me/} ]]
	then return 1
	else return 0
	fi
}

red_echo() {
	# This will print its arguments in a bright red iff
	# connected to a terminal (and otherwise won't, so
	# it won't throw off cat with weird terminal escapes)
	if [ -t 1 ]; then
		printf "\033[91m"
	fi
	echo $@
	if [ -t 1 ]; then
		printf "\033[39m"
	fi
}

if [ -e $(pwd)/cabal.sandbox.config ] || \
   [ -e $CABAL_SANDBOX_CONFIG/cabal.sandbox.config ]
then
	# If we're in a dir with a sandbox, or the env variable
	# CABAL_SANDBOX_CONFIG exists and there's a config there,
	# just exec cabal.
	exec cabal $@
elif contains_escape $@
then
	# If we aren't, but we've passed the --trust-me flag, then
	# remove that flag from the arguments and then exec into
	# cabal.
	red_echo "Executing despite not being in a sandbox..."
	ARGS=$@
	exec cabal ${ARGS[@]//--trust-me/}
else
	# Otherwise, print an appropriately ominous message and exit
	# with an error.
	red_echo "cabal: Not currently in a sandbox! To force execution, try"
	printf "    "
	red_echo "cabal $@ --trust-me"
	exit 2
fi