I've been using this Dockerfile to build a node based image.

# builder
FROM node:16-alpine as base
RUN npm install -g pnpm@next-7
WORKDIR /app
COPY package.json ./

FROM base as dependencies
RUN pnpm install

...

# development
FROM base as development
ENV NODE_ENV=development
COPY --from=dependencies --chown=node:node /app/node_modules ./node_modules
ENV NODE_ENV=development
USER node
CMD ["pnpm", "dev"]

The image is used in a development docker-compose.yml file like this:

version: '3.7'

services:
  frontend:
    ports:
      - '3000:3000'
    build:
      context: ../frontend
      target: development
    volumes:
      - ../frontend:/app
      - /app/node_modules
    command: >
      sh -c "cd /app && npm run dev"

As you can see, I'm not using the node_modules from the host (partially because I'm using Rush to manage the project with pnpm), but rather installing them again when the image is built.

If it weren't for - /app/node_modules anonymous volume, the host node_modules directory will be used inside the container. Since pnpm uses hard links when installing dependencies, the container would complain about wrong paths. But since the row is there, the container's node_modules shadows the host's one.

Installing new dependencies

How do you install a new dependency when needed? Issuing npm i brand-new-dependency on the host updates the package.json file. When the new image is built, it should thus include the new dependency as well. I had hard time to find out that wasn't the case though as the app failed to start saying brand-new-dependency does not exist.

It seems the anonymous volume is cached forever, no matter the changes in the underlying data.

How to refresh an anonymous volume

Once I realized that, it didn't take me long to find the way to refresh the volume when needed (e.g. with every new dependency installed). Here's a part of my Makefile that:

• forces service container to stop
• removes it
• removes any anonymous volumes attached to the container (that's what -v flag does)
• builds the service again
• runs the service

rebuild: ## rebuilds services (useful when dependecies change), e.g. ENVIRONMENT=DEV SERVICE=frontend make rebuild
	cd ./docker && docker-compose $${DOCKER_COMPOSE_$(ENVIRONMENT)} rm --force --stop -v $(SERVICE) && docker-compose $${DOCKER_COMPOSE_$(ENVIRONMENT)} build $(SERVICE) && docker-compose $${DOCKER_COMPOSE_$(ENVIRONMENT)} up $(SERVICE)

It supports different environments and services that are passed as variables: ENVIRONMENT=DEV SERVICE=frontend make rebuild.