How to avoid node_modules folder being deleted - docker

Question

I'm trying to create a Docker container to act as a test environment for my application. I am using the following Dockerfile:
FROM node:14.4.0-alpine
WORKDIR /test
COPY package*.json ./
RUN npm install .
CMD [ "npm", "test" ]
As you can see, it's pretty simple. I only want to install all dependencies but NOT copy the code, because I will run that container with the following command:
docker run -v `pwd`:/test -t <image-name>
But the problem is that node_modules directory is deleted when I mount the volume with -v. Any workaround to fix this?

Answer 1

When you bind mount test directory with $PWD, you container test directory will be overridden/mounted with $PWD. So you will not get your node_modules in test directory anymore.
To fix this issue you can use two options.
You can run npm install in separate directory like /node and mount your code in test directory and export node_path env like export NODE_PATH=/node/node_modules
then Dockerfile will be like:
FROM node:14.4.0-alpine
WORKDIR /node
COPY package*.json ./
RUN npm install .
WORKDIR /test
CMD [ "npm", "test" ]
Or you can write a entrypoint.sh script that will copy the node_modules folder to the test directory at the container runtime.
FROM node:14.4.0-alpine
WORKDIR /node
COPY package*.json ./
RUN npm install .
WORKDIR /test
COPY Entrypoint.sh ./
ENTRYPOINT ["Entrypoint.sh"]
and Entrypoint.sh is something like
#!/bin/bash
cp -r /node/node_modules /test/.
npm test

Answer 2

Approach 1
A workaround is you can do
CMD npm install && npm run dev
Approach 2
Have docker install node_modules on docker-compose build and run the app on docker-compose up.
Folder Structure
docker-compose.yml
version: '3.5'
services:
api:
container_name: /$CONTAINER_FOLDER
build: ./$LOCAL_FOLDER
hostname: api
volumes:
# map local to remote folder, exclude node_modules
- ./$LOCAL_FOLDER:/$CONTAINER_FOLDER
- /$CONTAINER_FOLDER/node_modules
expose:
- 88
Dockerfile
FROM node:14.4.0-alpine
WORKDIR /test
COPY ./package.json .
RUN npm install
# run command
CMD npm run dev