Misc package manager handling refactor (#1680)

Split out of the Poetry PR to keep that one smaller.

bin/compile

@@ -19,6 +19,7 @@ ENV_DIR="${3}"
 BUILDPACK_DIR=$(cd "$(dirname "$(dirname "${BASH_SOURCE[0]}")")" && pwd)
 
 source "${BUILDPACK_DIR}/bin/utils"
+source "${BUILDPACK_DIR}/lib/utils.sh"
 source "${BUILDPACK_DIR}/lib/cache.sh"
 source "${BUILDPACK_DIR}/lib/hooks.sh"
 source "${BUILDPACK_DIR}/lib/metadata.sh"
@@ -27,7 +28,6 @@ source "${BUILDPACK_DIR}/lib/package_manager.sh"
 source "${BUILDPACK_DIR}/lib/pip.sh"
 source "${BUILDPACK_DIR}/lib/pipenv.sh"
 source "${BUILDPACK_DIR}/lib/python_version.sh"
-source "${BUILDPACK_DIR}/lib/utils.sh"
 
 compile_start_time=$(nowms)
 
@@ -75,6 +75,7 @@ PROFILE_PATH="$BUILD_DIR/.profile.d/python.sh"
 EXPORT_PATH="${BUILDPACK_DIR}/export"
 GUNICORN_PROFILE_PATH="$BUILD_DIR/.profile.d/python.gunicorn.sh"
 WEB_CONCURRENCY_PROFILE_PATH="$BUILD_DIR/.profile.d/WEB_CONCURRENCY.sh"
+python_home='/app/.heroku/python'
 
 export PATH="/app/.heroku/python/bin:${PATH}"
 # Tell Python to not buffer it's stdin/stdout.
@@ -156,14 +157,13 @@ meta_time "python_install_duration" "${install_python_start_time}"
 
 # Install the package manager and related tools.
 package_manager_install_start_time=$(nowms)
-bundled_pip_module_path="$(utils::bundled_pip_module_path "${BUILD_DIR}")"
 case "${package_manager}" in
 	pip)
-		pip::install_pip_setuptools_wheel "${bundled_pip_module_path}" "${python_major_version}"
+		pip::install_pip_setuptools_wheel "${python_home}" "${python_major_version}"
 		;;
 	pipenv)
 		# TODO: Stop installing pip when using Pipenv.
-		pip::install_pip_setuptools_wheel "${bundled_pip_module_path}" "${python_major_version}"
+		pip::install_pip_setuptools_wheel "${python_home}" "${python_major_version}"
 		pipenv::install_pipenv
 		;;
 	*)

bin/utils

@@ -41,15 +41,3 @@ is_module_available() {
 	local module_name="${1}"
 	python -c "import sys, importlib.util; sys.exit(0 if importlib.util.find_spec('${module_name}') else 1)"
 }
-
-# The requirement versions are effectively buildpack constants, however, we want
-# Dependabot to be able to update them, which requires that they be in requirements
-# files. The requirements files contain contents like `package==1.2.3` (and not just
-# the package version) so we have to extract the version substring from it.
-get_requirement_version() {
-	local package_name="${1}"
-	local requirement
-	requirement=$(cat "${BUILDPACK_DIR}/requirements/${package_name}.txt")
-	local requirement_version="${requirement#"${package_name}=="}"
-	echo "${requirement_version}"
-}

lib/package_manager.sh

@@ -36,7 +36,9 @@ function package_manager::determine_package_manager() {
 		meta_set "setup_py_only" "false"
 	fi
 
-	case "${#package_managers_found[@]}" in
+	local num_package_managers_found=${#package_managers_found[@]}
+
+	case "${num_package_managers_found}" in
 		1)
 			echo "${package_managers_found[0]}"
 			return 0

lib/pip.sh

@@ -4,15 +4,18 @@
 # however, it helps Shellcheck realise the options under which these functions will run.
 set -euo pipefail
 
-PIP_VERSION=$(get_requirement_version 'pip')
-SETUPTOOLS_VERSION=$(get_requirement_version 'setuptools')
-WHEEL_VERSION=$(get_requirement_version 'wheel')
+PIP_VERSION=$(utils::get_requirement_version 'pip')
+SETUPTOOLS_VERSION=$(utils::get_requirement_version 'setuptools')
+WHEEL_VERSION=$(utils::get_requirement_version 'wheel')
 
 function pip::install_pip_setuptools_wheel() {
+	local python_home="${1}"
+	local python_major_version="${2}"
+
 	# We use the pip wheel bundled within Python's standard library to install our chosen
 	# pip version, since it's faster than `ensurepip` followed by an upgrade in place.
-	local bundled_pip_module_path="${1}"
-	local python_major_version="${2}"
+	local bundled_pip_module_path
+	bundled_pip_module_path="$(utils::bundled_pip_module_path "${python_home}")"
 
 	meta_set "pip_version" "${PIP_VERSION}"
 

lib/pipenv.sh

@@ -4,7 +4,7 @@
 # however, it helps Shellcheck realise the options under which these functions will run.
 set -euo pipefail
 
-PIPENV_VERSION=$(get_requirement_version 'pipenv')
+PIPENV_VERSION=$(utils::get_requirement_version 'pipenv')
 
 # TODO: Either enable or remove these.
 # export CLINT_FORCE_COLOR=1

lib/utils.sh

@@ -4,17 +4,29 @@
 # however, it helps Shellcheck realise the options under which these functions will run.
 set -euo pipefail
 
+# The requirement versions are effectively buildpack constants, however, we want
+# Dependabot to be able to update them, which requires that they be in requirements
+# files. The requirements files contain contents like `package==1.2.3` (and not just
+# the package version) so we have to extract the version substring from it.
+function utils::get_requirement_version() {
+	local package_name="${1}"
+	local requirement
+	requirement=$(cat "${BUILDPACK_DIR:?}/requirements/${package_name}.txt")
+	local requirement_version="${requirement#"${package_name}=="}"
+	echo "${requirement_version}"
+}
+
 # Python bundles pip within its standard library, which we can use to install our chosen
 # pip version from PyPI, saving us from having to download the usual pip bootstrap script.
 function utils::bundled_pip_module_path() {
-	local build_dir="${1}"
+	local python_home="${1}"
 
 	# We have to use a glob since the bundled wheel filename contains the pip version, which
 	# differs between Python versions. We also have to handle the case where there are multiple
 	# matching pip wheels, since in some versions of Python (eg 3.9.0) multiple versions of pip
 	# were accidentally bundled upstream. Note: This implementation relies upon `nullglob` being
 	# set, which is the case thanks to the `bin/utils` that was run earlier.
-	local bundled_pip_wheel_list=("${build_dir}"/.heroku/python/lib/python*/ensurepip/_bundled/pip-*.whl)
+	local bundled_pip_wheel_list=("${python_home}"/lib/python*/ensurepip/_bundled/pip-*.whl)
 	local bundled_pip_wheel="${bundled_pip_wheel_list[0]}"
 
 	if [[ -z "${bundled_pip_wheel}" ]]; then