How to disable warnings when node is launched via a (global) shell script

Question

I am building a CLI tool with node, and want to use the fs.promise API. However, when the app is launched, there's always an ExperimentalWarning, which is super annoying and messes up with the interaction prompts. How can I disable this warning/all warnings?

I'm testing this with the latest node v10 lts release on Windows 10.

To use the CLI tool globally, I have added this to my package.json file:

    { 
      //...
      "preferGlobal": true,
      "bin": { "myapp" : "./index.js" }
      //...
    }

And have run npm link to link the ./index.js script. Then I am able to run the app globally simply with myapp.

After some research I noticed that there are generally 2 ways to disable the warnings:

set environmental variable NODE_NO_WARNINGS=1
call the script with node --no-warnings ./index.js

Although I was able to disable the warnings with the 2 methods above, there seems to be no way to do that while directly running myapp command.

The shebang I placed in the entrance script ./index.js is:

#!/usr/bin/env node


// my code...

I have also read other discussions on modifying the shebang, but haven't found a universal/cross-platform way to do this - to either pass argument to node itself, or set the env variable.

If I publish this npm package, it would be great if there's a way to make sure the warnings of this single package are disabled in advance, instead of having each individual user tweak their environment themselves. Is there any hidden npm package.json configs that allow this?

Any help would be greatly appreciated!

Gilbert · Accepted Answer · 2024-01-01 19:42:56Z

37

I configured my test script like this:

 "scripts": {
    "test": "tsc && cross-env NODE_OPTIONS=--experimental-vm-modules NODE_NO_WARNINGS=1 jest"
  },

Notice the NODE_NO_WARNINGS=1 part. It disables the warnings I was getting from setting NODE_OPTIONS=--experimental-vm-modules

Update

Consider using vitest, the Next Generation Testing Framework. I find it much easier to configure. It's also Jest compatible

edited Jan 1, 2024 at 19:42

answered Jan 18, 2022 at 11:51

Gilbert

3,42232 silver badges40 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Blazing Fast · Accepted Answer · 2019-05-12 03:14:08Z

26

I am now using a launcher script to spawn a child_process to work around this limitation. Ugly, but it works with npm link, global installs and whatnot.

#!/usr/bin/env node
const { spawnSync } = require("child_process");
const { resolve } = require("path");

// Say our original entrance script is `app.js`
const cmd = "node --no-warnings " + resolve(__dirname, "app.js");
spawnSync(cmd, { stdio: "inherit", shell: true });

As it's kind of like a hack, I won't be using this method next time, and will instead be wrapping the original APIs in a promise manually, sticking to util.promisify, or using the blocking/sync version of the APIs.

answered May 12, 2019 at 3:14

Blazing Fast

9291 gold badge9 silver badges12 bronze badges

1 Comment

ivanjermakov Oct 29 at 19:15

Kind of like a hack? Hackiest hack of all time.

danday74 · Accepted Answer · 2024-07-30 21:57:29Z

21

You want --disable-warning=ExperimentalWarning

"scripts": {
  "start": "nodemon server.js",
  "test": "winpty node --experimental-vm-modules --disable-warning=ExperimentalWarning node_modules/jest/bin/jest.js"
}

This only suppresses experimental warnings and is thus more specific than the broader --no-warnings

answered Jul 30, 2024 at 21:57

danday74

58k56 gold badges273 silver badges337 bronze badges

5 Comments

Shenk Over a year ago

Thank you for this. It was exactly what I was looking for, since disabling every warning is not always desired. And the question did state "this warning" as one of the desires.

silverwind Over a year ago

Note that this requires Node 21.3.0 or higher

G-Force Over a year ago

seems to also work in 20.18, although I agree the blog says it's introduced in 21.3.0

kjw0188 Dec 12, 2024 at 23:19

I checked the release notes ad this was back ported to 20.11.0

Ferdinand Prantl Jul 23 at 23:37

The actual parameter is --no-warnings=ExperimentalWarning. Tested with node.js 22.17.1.

sad comrade · Accepted Answer · 2023-02-22 17:54:55Z

14

I needed to suppress:

ExperimentalWarning: Importing JSON modules is an experimental feature and might change at any time

And this worked for me on Windows, Node.js 18.x:

#!/usr/bin/env node --no-warnings

After install --no-warnings added to node calls inside bin scripts .cmd, .ps

I guess this won't work for Linux. I didn't manage to find universal solution

Related discussions:

answered Feb 22, 2023 at 17:54

sad comrade

1,52121 silver badges22 bronze badges

1 Comment

Mr Pablo Over a year ago

This was the quickest and most efficient fix for my situation!

Flion · Accepted Answer · 2022-08-29 08:12:42Z

13

New answer: You can also catch emitted warnings in your script and choose which ones to prevent from being logged

const originalEmit = process.emit;
process.emit = function (name, data, ...args) {
  if (
    name === `warning` &&
    typeof data === `object` &&
    data.name === `ExperimentalWarning` 
    //if you want to only stop certain messages, test for the message here:
    //&& data.message.includes(`Fetch API`)
  ) {
    return false;
  }
  return originalEmit.apply(process, arguments);
};

Inspired by this patch to yarn

answered Aug 29, 2022 at 8:12

Flion

11.1k14 gold badges54 silver badges77 bronze badges

1 Comment

Thorr Stevens Jun 19 at 19:39

This was the answer I was looking for. The real solution if you don't manage what spawned the script.

Sandro Pasquali · Accepted Answer · 2023-10-30 18:22:32Z

11

You can always remove the warning listener on your running process:

process.removeAllListeners('warning');

You might also recreate a listener (process.on('warning', warning => ...)) that can catch these warnings and give your process a chance to execute some custom behaviors (maybe ignore some, show others...).

answered Oct 30, 2023 at 18:22

Sandro Pasquali

5595 silver badges12 bronze badges

Comments

hexten · Accepted Answer · 2020-08-12 16:32:41Z

5

Here's what I'm using to run node with a command line flag:

#!/bin/sh
_=0// "exec" "/usr/bin/env" "node" "--experimental-repl-await" "$0" "$@"

// Your normal Javascript here

The first line tells the shell to use /bin/sh to run the script. The second line is a bit magical. To the shell it's a variable assignment _=0// followed by "exec" ....

Node sees it as a variable assignment followed by a comment - so it's almost a nop apart from the side effect of assigning 0 to _.

The result is that when the shell reaches line 2 it will exec node (via env) with any command line options you need.

answered Aug 12, 2020 at 16:32

hexten

1,1877 silver badges10 bronze badges

Comments

Reinsbrain · Accepted Answer · 2025-03-23 15:14:23Z

0

thanks to @sliverwind who noted the problem only happens in versions below 21.3.0. So the solution, today and going forward, seems to be to simply upgrade to nodejs lts.

answered Mar 23 at 15:14

Reinsbrain

2,6412 gold badges27 silver badges40 bronze badges

Comments

BananaAcid · Accepted Answer · 2025-03-31 21:17:15Z

I had the same problem not being able to get rid of the warings and when pressing CTRl+C, I got an await toplevel not fulfilled error (because the script was exiting out while awaiting, cathcing errors and more did not work for me).

So updated the script from @Blazing-Fast ( https://stackoverflow.com/a/56095929/1644202 ) and updated it:

#!/usr/bin/env node

import { spawnSync } from 'node:child_process';
import { resolve } from 'node:path';

// Say our original entrance script is `.../index.ts`
const cmd = 'node --no-warnings=ExperimentalWarning "' + resolve(import.meta.dirname, '..', 'index.ts' + '"');
spawnSync(cmd, { stdio: 'inherit', shell: true });

Mind the quotes around the filename: If the path has spaces, it would break otherwise.

Collectives™ on Stack Overflow

How to disable warnings when node is launched via a (global) shell script

9 Answers 9

Comments

1 Comment

5 Comments

1 Comment

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

9 Answers 9

Comments

1 Comment

5 Comments

1 Comment

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related