How to refresh Docker anonymous volumes


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

``` docker
# 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:

``` yaml
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](https://rushjs.io/) 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

``` bash
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`.
