package.main with -- arguments not working when running an npm script

[madarche]

• nodemon -v: 2.0.6
• node -v: 12.18.2
• Operating system/terminal environment: Debian GNU/Linux stable
• Using Docker? What image: No
• Command you ran: npm run start:watch -- -L -opt2 -opt3

Expected behaviour

[nodemon] starting `node src/main.js -L -opt2 -opt3

Actual behaviour

[nodemon] starting `node -opt2 -opt3 src/main.js`
node: bad option: -opt2
node: bad option: -opt3
[nodemon] app crashed - waiting for file changes before starting...

Steps to reproduce

package.json:

{
  "scripts": {
    "start": "node src/main.js",
    "start:watch": "nodemon"
  },
  "main": "src/main.js",
  "devDependencies": {
    "nodemon": "2.0.6"
  }
}

$ npm run start:watch -- -L -opt2 -opt3

> @ start:watch /home/joe/myapp
> nodemon "-L" "-opt2" "-opt3"

[nodemon] 2.0.6
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node -opt2 -opt3 src/main.js`
node: bad option: -opt2
node: bad option: -opt3
[nodemon] app crashed - waiting for file changes before starting...

While the following works fine:

$ node_modules/.bin/nodemon -- -L -opt2 -opt3
[nodemon] 2.0.6
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node src/main.js -L -opt2 -opt3`

This is related with https://github.com/remy/nodemon/blob/master/faq.md#my-script-arguments-are-being-taken-by-nodemon, #1773 and #1758

[remy]

Yeah… so, you're hitting some interesting combination of using nodemon and npm with the "stop eating" double dash thing.

When you run a program (any) with the -- argument, it takes everything after and passes it to the sub process.

So when you run the npm command npm run start:watch -- -L -opt2 -opt3 what nodemon sees is: nodemon -L -opt2 -opt3 - because npm has removed the -- from the arguments.

When nodemon runs with -L -opt2 -opt3 it recognises the -L as being for itself (i.e. it's a nodemon specific flag) and the unknown flags are treated as flags for the executing process, ie. node. Which is why you're seeing the weird starting mode: node -opt2 -opt3 src/main.js

There two work arounds for this:

1. Kinda ugly, but this will work - add another --: npm run start:watch -- -- -L -opt2 -opt3 - I'm not keen, but it works without any changes to your code.
2. A small tweak to your package, set "start:watch": "nodemon src/main.js" now doing npm run start:watch -- -L -opt2 -opt3, the -L goes to nodemon (for "legacy mode") and the options go to your script.

I might add this to the faq too actually.

Finally, thank you so much for your sponsorship and support - genuinely valued.

[madarche]

@remy as for the sponsorship, this need was the right opportunity to thank you, this was long overdue!

[madarche]

To be complete, I should have added that I run successfully npm run start:watch -- -L -opt2 -opt3 on many projects, but those projects don't have a package.main.

[madarche]

The solution of using "start:watch": "nodemon src/main.js" in package.json fits me fine because that way the developers can always use the same command npm run start:watch -- -L -opt2 -opt3 on all projects!

Thank you @remy