Enable Bash exit on undefined variables (set -u) (#1646)

Since it's a best practice that helps make bugs more visible.

Aside from the `DEBUG_COLLECTSTATIC` change, all of the
others only affect buildpack internals.

GUS-W-16864420.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Fixed Django collectstatic debug output being shown if `DEBUG_COLLECTSTATIC` was set to `0` or the empty string. ([#1646](https://github.com/heroku/heroku-buildpack-python/pull/1646))
 - Stopped adding a trailing `:` to `C_INCLUDE_PATH`, `CPLUS_INCLUDE_PATH`, `LIBRARY_PATH`, `LD_LIBRARY_PATH` and `PKG_CONFIG_PATH`. ([#1645](https://github.com/heroku/heroku-buildpack-python/pull/1645))
 - Removed remnants of the unused `.heroku/vendor/` directory. ([#1644](https://github.com/heroku/heroku-buildpack-python/pull/1644))
 

bin/compile

@@ -2,9 +2,12 @@
 # Usage: bin/compile <build-dir> <cache-dir> <env-dir>
 # See: https://devcenter.heroku.com/articles/buildpack-api
 
-set -eo pipefail
+set -euo pipefail
 
-[[ -n "$BUILDPACK_XTRACE" ]] && set -o xtrace
+# Note: This can't be enabled via app config vars, since at this point they haven't been loaded from ENV_DIR.
+if [[ "${BUILDPACK_XTRACE:-0}" == "1" ]]; then
+	set -o xtrace
+fi
 
 BUILD_DIR="${1}"
 CACHE_DIR="${2}"

bin/release

@@ -12,12 +12,8 @@ BUILDPACK_DIR=$(cd "$(dirname "$(dirname "${BASH_SOURCE[0]}")")" && pwd)
 # Unfortunately the build system doesn't source the `export` script before
 # running `bin/release`, so we have to do so manually to ensure the buildpack
 # Python is used by `is_module_available` instead of system Python.
-# We also have to disable Bash error on undefined variables, since not all env
-# vars used in the export script will be set by default (eg `LIBRARY_PATH`).
-set +u
 # shellcheck source=/dev/null
 source "${BUILDPACK_DIR}/export"
-set -u
 
 source "${BUILDPACK_DIR}/bin/utils"
 

bin/report

@@ -26,14 +26,10 @@ BUILDPACK_DIR=$(cd "$(dirname "$(dirname "${BASH_SOURCE[0]}")")" && pwd)
 
 # The build system doesn't source the `export` script before running this script, so we have to do
 # so manually (if it exists) so that buildpack Python/pip can be found (if the build succeeded).
-# We have to disable Bash error on undefined variables for now, since not all env vars used in the
-# export script will be set by default (eg `LIBRARY_PATH`).
 EXPORT_FILE="${BUILDPACK_DIR}/export"
 if [[ -f "${EXPORT_FILE}" ]]; then
-	set +u
 	# shellcheck source=/dev/null
 	source "${EXPORT_FILE}"
-	set -u
 fi
 
 source "${BUILDPACK_DIR}/lib/metadata.sh"

bin/steps/collectstatic

@@ -12,7 +12,7 @@
 
 # This script is run in a subshell via sub_env so doesn't inherit the options/vars/utils from `bin/compile`.
 # TODO: Stop running this script in a subshell.
-set -eo pipefail
+set -euo pipefail
 BUILDPACK_DIR=$(cd "$(dirname "$(dirname "$(dirname "${BASH_SOURCE[0]}")")")" && pwd)
 source "${BUILDPACK_DIR}/bin/utils"
 
@@ -92,7 +92,7 @@ echo
 echo "       https://devcenter.heroku.com/articles/django-assets"
 
 # Additionally, dump out the environment, if debug mode is on.
-if [[ -n "$DEBUG_COLLECTSTATIC" ]]; then
+if [[ "${DEBUG_COLLECTSTATIC:-0}" == "1" ]]; then
 	echo
 	echo "****** Collectstatic environment variables:"
 	echo

bin/steps/nltk

@@ -2,7 +2,7 @@
 
 # This script is run in a subshell via sub_env so doesn't inherit the options/vars/utils from `bin/compile`.
 # TODO: Stop running this script in a subshell.
-set -eo pipefail
+set -euo pipefail
 BUILDPACK_DIR=$(cd "$(dirname "$(dirname "$(dirname "${BASH_SOURCE[0]}")")")" && pwd)
 source "${BUILDPACK_DIR}/bin/utils"
 

bin/steps/python

@@ -144,7 +144,7 @@ if [[ -f "${BUILD_DIR}/requirements.txt" ]]; then
 	fi
 fi
 
-if [[ -n "${SKIP_INSTALL}" ]]; then
+if [[ "${SKIP_INSTALL:-0}" == "1" ]]; then
 	puts-step "Using cached install of ${PYTHON_VERSION}"
 else
 	puts-step "Installing ${PYTHON_VERSION}"

bin/steps/sqlite3

@@ -5,7 +5,7 @@
 
 sqlite3_install() {
 	HEROKU_PYTHON_DIR="$1"
-	HEADERS_ONLY="$3"
+	HEADERS_ONLY="${3:-}"
 
 	mkdir -p "$HEROKU_PYTHON_DIR"
 

lib/pip.sh

@@ -52,7 +52,7 @@ function pip::install_dependencies() {
 	fi
 
 	# Install test dependencies, for Heroku CI.
-	if [[ -n "${INSTALL_TEST}" ]]; then
+	if [[ "${INSTALL_TEST:-0}" == "1" ]]; then
 		if [[ -f requirements-test.txt ]]; then
 			puts-step "Installing test dependencies..."
 			/app/.heroku/python/bin/pip install -r requirements-test.txt --exists-action=w --src='/app/.heroku/src' --disable-pip-version-check --no-cache-dir 2>&1 | cleanup | indent

lib/pipenv.sh

@@ -32,7 +32,7 @@ function pipenv::install_dependencies() {
 
 	# Install the test dependencies, for CI.
 	# TODO: This is currently inconsistent with the non-test path, since it assumes (but doesn't check for) a lockfile.
-	if [[ -n "${INSTALL_TEST}" ]]; then
+	if [[ "${INSTALL_TEST:-0}" == "1" ]]; then
 		puts-step "Installing test dependencies with Pipenv"
 		/app/.heroku/python/bin/pipenv install --dev --system --deploy --extra-pip-args='--src=/app/.heroku/src' 2>&1 | cleanup | indent
 

vendor/buildpack-stdlib_v8.sh

@@ -65,7 +65,7 @@ sub_env() {
 	(
 		# TODO: Fix https://github.com/heroku/buildpack-stdlib/issues/37
 		# shellcheck disable=SC2153
-		export_env "$ENV_DIR" "$WHITELIST" "$BLACKLIST"
+		export_env "$ENV_DIR" "${WHITELIST:-}" "${BLACKLIST:-}"
 
 		"$@"
 	)