Order a Dockerfile for the Build Cache

Labs have no container engine, so nothing is built or started: your files are checked by reading them, the way a reviewer or a CI linter would. docker-compose config (to validate Compose files) and hadolint (a Dockerfile linter) are installed.

Every code change to /home/student/projects/invoice-pdf makes CI reinstall all npm packages, which takes four minutes.

Task

Reorder /home/student/projects/invoice-pdf/Dockerfile so that the dependency install is cached until the dependencies change:

• copy only package.json and package-lock.json, then run npm ci --omit=dev
• copy the rest of the source after that
• keep the same base image, working directory, exposed port and start command