Node --experimental-modules - Error: Cannot find module

I am getting an error when trying to import a local file, though no problem when using npm packages.

#server.js

import express from 'express'
import next from 'next'

import apis from './src/server/api'

#api.js

export default {
  ello: 'bye',
  jamie: 'hey'
}

#Starting app

node --experimental-modules --inspect server.js

#Error

For help, see: https://nodejs.org/en/docs/inspector
(node:20153) ExperimentalWarning: The ESM module loader is experimental.
internal/modules/esm/default_resolve.js:59
  let url = moduleWrapResolve(specifier, parentURL);
            ^

Error: Cannot find module '/var/www/goldendemon.hutber.com/src/server/api' imported from /var/www/goldendemon.hutber.com/server.js
    at Loader.resolve [as _resolve] (internal/modules/esm/default_resolve.js:59:13)
    at Loader.resolve (internal/modules/esm/loader.js:70:33)
    at Loader.getModuleJob (internal/modules/esm/loader.js:143:40)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:43:40)
    at link (internal/modules/esm/module_job.js:42:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

I'm answering my own question if anybody else has this problem.

It turns out in experimental mode you need to define the full path with extension. So I am trying to import index.js thinking it will know.

To fix it:

import express from 'express'
import next from 'next'
import api from './src/server/api/index.js'

on node 12 you have 2 options:

1. use type="module" on package.json, experimental modules and specify extensions with specidier-resolution like this: node --experimental-modules --es-module-specifier-resolution=node src/index

2. or not using specifier-resolution. Keep in mind you'll have to specify the extension of your files every where.

It should also work if you name your module file with a .mjs extension. Also, other ways to enable ESM are mentioned here.

> Node.js will treat the following as ES modules when passed to node as the initial input, or when referenced by import statements within ES module code: > > - Files ending in .mjs. > > - Files ending in .js, or extensionless files, when the nearest parent package.json file contains a top-level field "type" with a value of "module". > > - Strings passed in as an argument to --eval or --print, or piped to node via STDIN, with the flag --input-type=module.

Or do like I did and just use transpilation the minute your source code deals with ES style module imports or some other non-standard JavaScript code, (E.g. TypeScript) on Node. For reference see this quick bash script I wrote, saved as .script/run-it.sh inside of my Node project:

#!/bin/bash

script=$1
out_path==/tmp/$script-out.js
npx esbuild --platform=node --bundle --outfile=$out_path $script
node $out_path 

I added it as a run script in my package.json:

"scripts": {
    "test": "sst test",
    "start": "sst start",
    "build": "sst build",
    "deploy": "sst deploy",
    "remove": "sst remove",
    "run-it": "./.script/run-it.sh"
  },

And my target script (import-test.js), what I want to emit/transpile as JavaScript code:

import { default as myImport } from './lib/index.js'
console.log(myImport)

And now I run it:

$ npm run run-it ./import-test.js 

> [email protected] run-it /Users/jmquij0106/git/a-rebalancing-act
> ./.script/run-it.sh "./import-test.js"

[Function: main]

Bottomline is spare yourself the pain and just emit CommonJS compliant code whenever dealing with ES Modules on Node.js, see this comment/issue.