bootstrap-python

#!/usr/bin/env bash

# Compile script is executed from /home/vcap and buildpack is downloaded in /tmp/buildpacks/<<something>>/
# Determine the buildpack folder based on this file
BUILDPACK_PATH=$(dirname "$0")/..
BUILD_PATH=$1
CACHE_PATH=$2

# Silence warning about outdated pip version
export PIP_DISABLE_PIP_VERSION_CHECK=1

# Bootstrap and install the Python requirements from wheels.
# Minimal packaging for the buildpack includes pip and setuptools wheels.
REQUIREMENTS_PATH="${BUILDPACK_PATH}/requirements.txt"
WHEELS_PATH="${BUILDPACK_PATH}/vendor/wheels"
PIP_WHL_PATH=$(ls $WHEELS_PATH/pip*.whl 2>/dev/null | head -n1)

PIP_VERBOSITY_FLAGS=""
if [[ -z $BUILDPACK_XTRACE ]] || [[ $BUILDPACK_XTRACE == "false" ]]
then
    PIP_VERBOSITY_FLAGS="--quiet"
fi

PIP_WHEELDIR="${CACHE_PATH}/pip/wheels"
mkdir -p $PIP_WHEELDIR
# Set the correct Python site-packages directory to install to
SITE_PACKAGES_PATH="${BUILD_PATH}/$(python3 -m site --user-site | cut -d '/' -f4-)"

# Invalidate the cache and copy over wheels if they are bundled
# If no wheels are included, the cache will be left alone, as dependencies are downloaded
echo " ---> Check if Python dependencies need to be cached..."
if [[ $(ls -1q $WHEELS_PATH/* 2>/dev/null | wc -l) -gt 0 ]] && [[ $(diff $WHEELS_PATH $PIP_WHEELDIR 2>/dev/null | wc -l) -gt 0 ]]
then
    echo " ---> Invalidating Python wheels cache..."
    rm -rf $PIP_WHEELDIR
    echo " ---> Copying bundled Python dependencies to cache...";
    mkdir -p $PIP_WHEELDIR
    cp -rf $WHEELS_PATH/* $PIP_WHEELDIR/ 2>/dev/null
fi

echo " ---> Bootstrapping pip..."
if [ "$CF_STACK" == "cflinuxfs4" ]; then
  PIP_CMD="pip3"
else
  PIP_CMD="pip"
fi

if ! [[ -x "$(command -v ${PIP_CMD})" ]]
then
    # pip is not included on the root FS
    if [[ -n "${PIP_WHL_PATH}" ]]
    then
        # Bootstrap wheels are bundled in the buildpack
        python3 ${PIP_WHL_PATH}/pip install $PIP_VERBOSITY_FLAGS --user --no-warn-script-location --no-index --no-build-isolation --find-links=$PIP_WHEELDIR --use-pep517 pip setuptools wheel
    else
        # Bootstrap wheels are not bundled in the buildpack
        curl -sS https://bootstrap.pypa.io/pip/get-pip.py -o get-pip.py
        python3 get-pip.py install $PIP_VERBOSITY_FLAGS --user --no-warn-script-location
    fi
    PIP_CMD="/home/vcap/.local/bin/pip"
else
    # pip is bundled on the root FS
    if [ "$CF_STACK" == "cflinuxfs4" ]; then
      PIP_CMD="python3 $(dirname "$(command -v python3)")/pip3"
    fi
    $PIP_CMD install --upgrade --user --no-warn-script-location --use-pep517 pip setuptools wheel
fi

# Only download Python dependencies if they are not bundled
if [[ $(ls -1q $WHEELS_PATH/* 2>/dev/null | wc -l) -gt 0 ]]
then
    echo " ---> Using bundled Python dependencies"
else
    echo " ---> Downloading Python dependencies..."
    $PIP_CMD download $PIP_VERBOSITY_FLAGS --use-pep517 -r $REQUIREMENTS_PATH --prefer-binary -d $PIP_WHEELDIR
fi

echo " ---> Installing Python dependencies to ${SITE_PACKAGES_PATH}..."
$PIP_CMD install $PIP_VERBOSITY_FLAGS --target $SITE_PACKAGES_PATH --prefer-binary --no-warn-script-location --no-index --no-build-isolation --find-links=$PIP_WHEELDIR --use-pep517 -r $REQUIREMENTS_PATH
echo " ---> Finished installing Python dependencies"