armbian-build/extensions/detect-unused-extensions.sh

## Configuration
export LOG_ALL_HOOK_TRACES=no # Should we log all hook function traces to stdout? (no, or level: wrn info)

## Hooks

# A honeypot wishful hooking. To make sure the whole thing works.
# This is exactly the kind of hooking this extension is meant to detect.
# This will never run, and should be detected below, but is handled specially and ignored.
# Note: this will never run, since we (hopefully) don't have a hook_point called 'wishful_hooking_example'.
function wishful_hooking_example__this_will_never_run() {
	echo "WISHFUL HOOKING -- this will never run. I promise."
}

# Run super late, hopefully at the last possible moment.
function extension_metadata_ready__999_detect_wishful_hooking() {
	display_alert "Checking extensions and hooks for uncalled hook points"
	declare -i found_honeypot_function=0

	# Loop over the defined functions' keys. Find the info about the call. If not found, warn the user.
	# shellcheck disable=SC2154 # hook-exported variable
	for one_defined_function in ${!defined_hook_point_functions[*]}; do
		local source_info defined_info line_info
		defined_info="${defined_hook_point_functions["${one_defined_function}"]}"
		source_info="${hook_point_function_trace_sources["${one_defined_function}"]}"
		line_info="${hook_point_function_trace_lines["${one_defined_function}"]}"
		stack="$(get_extension_hook_stracktrace "${source_info}" "${line_info}")"
		if [[ "$source_info" != "" ]]; then
			# log to debug log. it's reassuring.
			echo "\$\$\$ Hook function stacktrace for '${one_defined_function}': '${stack}' (${defined_info})" >> "${EXTENSION_MANAGER_LOG_FILE}"
			if [[ "${LOG_ALL_HOOK_TRACES}" != "no" ]]; then
				display_alert "Hook function stacktrace for '${one_defined_function}'" "${stack}" "${LOG_ALL_HOOK_TRACES}"
			fi
			continue # found a caller, move on.
		fi

		# special handling for the honeypot function. it is supposed to be always detected as uncalled.
		if [[ "${one_defined_function}" == "wishful_hooking_example__this_will_never_run" ]]; then
			# we expect this wishful hooking, it is done on purpose below, to make sure this code works.
			found_honeypot_function=1
		else
			# unexpected wishful hooking. Log and wrn the user.
			echo "\$\$\$ Wishful hooking detected" "Function '${one_defined_function}' is defined (${defined_info}) but never called by the build." >> "${EXTENSION_MANAGER_LOG_FILE}"
			display_alert "Wishful hooking detected" "Function '${one_defined_function}' is defined (${defined_info}) but never called by the build." "wrn"
		fi
	done

	if [[ $found_honeypot_function -lt 1 ]]; then
		display_alert "Wishful hook DETECTION FAILED" "detect-wishful-hooking is not working. Good chance the environment vars are corrupted. Avoid child shells. Sorry." "wrn" | tee -a "${EXTENSION_MANAGER_LOG_FILE}"
	fi
}