Setup virtualenv for a Google App Engine project

setup_gae_virtualenv.sh

#!/bin/sh

# Script for setting up virtualenv to work correctly with Google App Engine projects
# @author Karol Kuczmarski "Xion"


DEFAULT_APPENGINE_SDK_PATH="/opt/google_appengine"
DEFAULT_PROJECT_LIB_PATH="./lib"


# Utility functions

error() {
    echo "$@" >&2;
}

fatal() {
    error "fatal: $@"
    exit
}

list_subdirectories() {
    local path=$(readlink -f "$1")  # make relative path absolute
    ls "$path/*" --directory --almost-all --format=single-column
}


# Handling virtualenv

ensure_mkvirtualenv() {
    which mkvirtualenv >/dev/null \
        || fatal "mkvirtualenv not found -- cannot create virtualenv!"
}

ensure_virtualenv() {
    if [ -z "$VIRTUAL_ENV" ]; then
        echo "virtualenv not detected!"

        ensure_mkvirtualenv
        printf "Enter the name to create one using virtualenvwrapper: "
        read virtualenv_name
        if [ -z "$virtualenv_name" ]; then
             fatal "Empty name -- aborting"
        fi

        mkvirtualenv "$virtualenv_name" --no-site-packages \
            || fatal "Failed creating virtualenv!"
        echo "virtualenv created."
    else
        echo "Using current virtualenv ($VIRTUAL_ENV)."
    fi
}

get_venv_site_packages_path() {
    local python_version=$(python -V 2>&1 | cut -d' ' -f 2)
    local short_version="${python_version%.*}"  # minor.major, like "2.7"
    echo "$VIRTUAL_ENV/lib/python$short_version/site-packages"
}


# Getting paths from the user

get_appengine_path() {
    local appengine_path

    read -p "Enter the path to Google App Engine Python SDK [$DEFAULT_APPENGINE_SDK_PATH]: " appengine_path
    if [ -z "$appengine_path" ]; then
        appengine_path=$DEFAULT_APPENGINE_SDK_PATH
    fi

    if [ ! -d "$appengine_path" ]; then
        fatal "App Engine SDK directory not found -- aborting"
    fi
    echo $appengine_path
}

get_project_lib_path() {
    local lib_path

    read -p "Enter the path to project's third party libraries [$DEFAULT_PROJECT_LIB_PATH]: " lib_path
    if [ -z "$lib_path" ]; then
        lib_path=$DEFAULT_PROJECT_LIB_PATH
    fi

    if [ ! -d "$lib_path" ]; then
        fatal "Project's libraries not found -- aborting"
    fi
    echo $lib_path
}


# Main script

prepare_gae_site_packages() {
    printf "Adding App Engine libs to site-packages..."
    local appengine_path=$1
    local gae_pth=$(echo $(get_venv_site_packages_path)/gae.pth)
    echo "$appengine_path" >"$gae_pth"
    list_subdirectories "$appengine_path"/lib >>"$gae_pth"
    echo "done."
}

prepare_lib_site_packages() {
    printf "Adding project libraries to site-packages..."
    local lib_path=$1
    local project_pth=$(echo $(get_venv_site_packages_path)/project.pth)

    # check for root __init__.py to see if libraries are self-contained
    # within subdirectories, or they are part of one Python package
    if [ -f "$lib_path"/__init__.py ]; then
        echo $lib_path >"$project_pth"
    else
        list_subdirectories "$lib_path" >"$project_pth"
    fi

    echo "done."
}

create_gae_tools_symlinks() {
    printf "Symlinking App Engine utilities..."
    local appengine_path=$1

    # dev_appserver.py breaks if its working dir is not root of GAE SDK
    dev_appserver_script=$VIRTUAL_ENV/bin/dev_appserver
    cat <<EOF >$dev_appserver_script
#!/bin/sh
$appengine_path/dev_appserver.py \$*
EOF
    chmod a+x $dev_appserver_script
    ln -s "$appengine_path"/appcfg.py $VIRTUAL_ENV/bin/appcfg

    echo "done."
}

main() {
    ensure_virtualenv

    local appengine_path=$(get_appengine_path)
    local project_lib_path=$(get_project_lib_path)

    prepare_gae_site_packages "$appengine_path"
    prepare_lib_site_packages "$project_lib_path"
    create_gae_tools_symlinks "$appengine_path"

    echo "Setup completed."
}

main