how to let npm package bin run with experimental-modules option?

Question

Starting in Node v8.5.0, support for ES6 style modules

import x from 'x'

has been available by running node using the option --experimental-modules, as below:

node --experimental-modules test.mjs

Using the bin key in package.json you can easily create cli tools npm cli, by running npm link.

Unfortunately, when running in this manner, node is called without the optional --experimental-modules flag.

How can you use bin modules with --experimental-modules?

Here is an example

bin/healthcheck.mjs

import { connect } from 'amqplib'

let open = connect(process.env.RABBITMQ_URL);

const exit = ({healthy = true}) => {
  return healthy ? process.exit(0) : process.exit(1)
}

open.then(() => {
  exit({healthy: true})
}).catch((e) => {
  exit({healthy: false})
})

package.json

{
  "name": "my-cli",
  "bin": {
    "healthcheck": "./bin/healthcheck.mjs"
  }
}

running...

> npm link
> healthcheck
/usr/local/bin/healthcheck: line 1: import: command not found
/usr/local/bin/healthcheck: line 3: syntax error near unexpected token `('
/usr/local/bin/healthcheck: line 3: `let open = connect(process.env.RABBITMQ_URL);'

Patrick Lee Scott · Accepted Answer · 2018-03-20 21:05:48Z

12

You can use a shebang at the top of the script

#!/bin/sh 
":" //# comment; exec /usr/bin/env node --experimental-modules "$0" "$@"

More details here: http://sambal.org/2014/02/passing-options-node-shebang-line/

answered Mar 20, 2018 at 21:05

Patrick Lee Scott

8,8093 gold badges40 silver badges43 bronze badges

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

4 Comments

Native Dev Over a year ago

Nice Patrick! In my simple use case, I just have this one-liner at the top of my entry-point file: #!/usr/bin/env node --experimental-modules --no-warnings. Thanks!

ChaseMoskal Over a year ago

it's shameful that in 2019, node still requires us to use this hack from early 2014 — so glad it works!

Brett Zamir Over a year ago

I get this error when it runs line 2: //#: No such file or directory. It continues running when I run it from Terminal, but it errs out in Sourcetree. Any idea if there is a way to solve? I removed "comment", and that didn't help.

Brett Zamir Over a year ago

Oops--nevermind--I see it was my adding a semicolon after ":"... Can't do that apparently

Collectives™ on Stack Overflow

how to let npm package bin run with experimental-modules option?

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related