Fix up build script

Author: mcdonnnj

.github/workflows/build.yml

@@ -153,7 +153,9 @@ jobs:
       # most likely be able leverage the functionality of upload-artifact v2(+)
       # to upload a single file as an artifact.
       - name: Unzip produced zip
-        run: unzip skeleton-aws-lambda.zip -d lambda_zip_contents
+        run: |
+          unzip skeleton-aws-lambda_${{ matrix.python-version }}.zip \
+            -d lambda_zip_contents
       - name: Upload artifacts
         uses: actions/upload-artifact@v2
         with:

build.sh

@@ -4,33 +4,95 @@ set -o nounset
 set -o errexit
 set -o pipefail
 
-if [ "$#" -ne 1 ]
-then
-  exit 1
-else
-  PY_VERSION="$1"
-fi
+PY_VERSION="3.8"
+FILE_BASE="skeleton-aws-lambda"
+
+# Print usage information and exit with the provided exit code.
+function usage {
+  echo "Usage:"
+  echo "  ${0##*/} [options]"
+  echo
+  echo "Options:"
+  echo "  -o, --output-file   BASENAME  Base output file name to use [default: $FILE_BASE]."
+  echo "  -p, --python-version VERSION  Python version to use [default: $PY_VERSION]."
+  echo "  -h, --help                    Display this message."
+  echo
+  echo "Notes:"
+  echo "- Outputs files in the format 'BASENAME_VERSION.zip'."
+  echo "- Requires Docker and Docker Compose."
+  exit "$1"
+}
+
+# Check for required external programs. If any are missing output a list of all
+# requirements and then exit.
+function check_dependencies {
+  required_tools="docker docker-compose"
+  for tool in $required_tools
+  do
+    if [ -z "$(command -v "$tool")" ]
+    then
+      echo "This script requires the following tools to run:"
+      for item in $required_tools
+      do
+        echo "- $item"
+      done
+      exit 1
+    fi
+  done
+}
+
+while (( "$#" ))
+do
+  case "$1" in
+    -h|--help)
+      usage 0
+      ;;
+    -o|--output-name)
+      if [ -n "$2" ] && [ "${2:0:1}" != "-" ]
+      then
+        FILE_BASE=$2
+        shift 2
+      else
+        usage 1
+      fi
+      ;;
+    -p|--python-version)
+      if [ -n "$2" ] && [ "${2:0:1}" != "-" ]
+      then
+        PY_VERSION=$2
+        shift 2
+      else
+        usage 1
+      fi
+      ;;
+    -*)
+      usage 1
+      ;;
+  esac
+done
+
+check_dependencies
 
 ###
 # Define the name of the Lambda zip file being produced.
 ###
-ZIP_FILE=skeleton-aws-lambda.zip
+ZIP_FILE="${FILE_BASE}_${PY_VERSION}.zip"
 
 ###
 # Set up the Python virtual environment.
 # We use --system-site-packages so the venv has access to the packages already
 # installed in the container to avoid duplicating what will be available in the
 # lambda environment on AWS.
 ###
-VENV_DIR=/venv
-python -m venv --system-site-packages $VENV_DIR
+VENV_DIR="/venv"
+python -m venv --system-site-packages "$VENV_DIR"
 
 # Here shellcheck complains because it can't follow the dynamic path.
 # The path doesn't even exist until runtime, so we must disable that
 # check.
 #
 # shellcheck disable=1090
-source $VENV_DIR/bin/activate
+source "$VENV_DIR/bin/activate"
 
 ###
 # Upgrade pip.
@@ -70,7 +132,7 @@ cp lambda_handler.py "$BUILD_DIR"
 ###
 # Zip it all up.
 ###
-OUTPUT_DIR=/output
+OUTPUT_DIR="/output"
 if [ ! -d "$OUTPUT_DIR" ]
 then
     mkdir "$OUTPUT_DIR"