Add launch option that allows run node project by npm script

[Ciget]

Hi all,

Looks like current trend to run NodeJs app via npm start or npm dev.
By default, launch.json does not allow us to do this. It`s very unusable. My suggection - to add this feature, that allow easily cconfigure how to run app and not just by parameter "node" and entry point to the site.

Thanks.

[weinand]

@Ciget a VS Code 'launch' configuration is used to launch 'node' in debug mode listening on a specific port. I'm not aware of a way to pass the debug-port to node via an "npm start". If you know a way how to do this, please let me know and we can consider to support "npm" as a launch option. Thanks.

[Ciget]

@weinand, thanks for quick reply. I`m asking this, because most of top solutions use this approach to run. So, does it means, that using VS Code we will do own way to develop app?

[weinand]

@Ciget no, you don't have to change the way of developing an app.

To start your app in debug mode you can use "npm dev" from the command line.

I assume that "npm dev" runs your app in debug mode like this:

"scripts": {
    "dev": "node --debug=12345 server.js"
}

In VS Code create an 'attach' configuration:

{
    "name": "Attach to server.js",
    "type": "node",
    "request": "attach",
    "port": 12345
}

Make sure that the debug port is identical to the one used in the "dev" script (or is 5858 if no port is specified in the dev script).

[egamma]

I was about to write the same, I've just used a more complex script as an example.
So the pattern is that you add an npm script for debugging, e.g., build_test_debug.

  "scripts": {
    "build_test": "rm -rf dist/ && npm run lint && npm run build_cjs && jasmine",
    "build_test_debug": "rm -rf dist/ && npm run lint && npm run build_cjs && jasmine --debug-brk
  }

This requires still two steps 1) npm run build_test_debug 2) F5 to attach.
@weinand would it make sense to support running an npm script as a preLaunchTask?

[weinand]

@egamma yes, it makes sense to run anything (including npm scripts) as a preLaunchTask. This is on our February 2016 plan (see #2263).

[tbeseda]

I'd also be interested in a way for the Launch feature to execute an npm task. 👍
The scripts property of a Node project's manifest is a common way to launch, build, debug, etc.

Also, FWIW, to run an arbitrary npm script like "dev" that isn't a part of the standard scripts use npm-run-script:

$ npm run dev

[jpierson]

I had posted on Stack Overflow about this exactly. It would be nice if this was more easily supported.

[weinand]

You all seem to have a clear picture how this feature should work.
I don't, so I'd appreciate if someone could help me.

A VS Code 'launch' configuration needs to pass the standard node debug argument '--debug-brk' and a port number to the runtime (e.g. 'node').

If the runtime is launched via an npm script, I still need a mechanism to pass the debug port into that script. What is the way to do this?

[jpierson]

I wonder if there is an environment variable alternative to --debug-brk?

Update:
Ah from the document under the configuration section.

environment variables prefixed with node-inspector_

[weinand]

@jpierson I don't see how node-inspector can help here? I'm looking for a way to pass a port number to an npm script. Ideally something like this:

npm run-script debug port=1234

VS Code would use this to pass a debug port to node and subsequently VS Code would try to attach to that port.

And the npm script would look like this:

    "scripts": {
        "debug": "node --debug-brk=${port} program.js",
    },