How can I attach VS Code to a node process running in a docker container

Question

I'm trying to attach the Visual Studio Code debugger to a node.js app that is running inside a Docker container.

I start the app like:

node --debug-brk app.js

I expose the debugger port in docker-compose.yml:

app:
  build: .
  working_dir: /code
  volumes:
    - .:/code
  command: npm run debug
  ports:
    - "3004:3000"
    - "5858:5858"

My launch.json looks like:

{
    "version": "0.1.0",
    "configurations": [
        {
            "name": "Attach",
            "type": "node",
            "address": "localhost",
            "port": 5858
        }
    ]
}

Now, when I start the application and attach the debugger this will correctly connect (I can see the values flashing in the debugger UI already), but then it will stop, telling me the following:

Error opening 'app.js' (File not found: /code/app.js).

This is due to the fact that docker will not mount the app in root but in /code (see volumes in docker-compose.yml) and VS code is confused by the sudden offset.

When I run the application outside the container (i.e. locally, without offset) it works just as expected and I can use the debugger as expected.

There seems to be a cwd option for the launch configuration but I am not sure if that makes any difference in my case.

Can I fix this path offset? Am I missing something else here?

Answer 1

This feature is now officially supported by VSCode: https://github.com/Microsoft/vscode-node-debug/issues/8