export * from 'dependency' not working when { "type": "module" }

[marcofranssen]

Node Version: v12.16.1
dependency esm version: 3.2.25

When "type": "module" is defined in package.json the following is not allowed in a file.

export * from './dep-a'
export * from './dep-b'
export * from './dep-c'
export * from './dep-d'

It gives the following error.

/Users/marco/code/my-project/lib/commands/index.js:1
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /Users/marco/code/my-project/lib/commands/index.js
require() of ES modules is not supported.
require() of /Users/marco/code/my-project/lib/commands/index.js from /Users/marco/code/my-project/bin/my-project is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.
Instead rename index.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from /Users/marco/code/my-project/package.json.

I would expect this code to completely valid.

The idea to define type module is to be able to use the node 13 feature out of the box when on node 13 and use esm in node 12.

Is this a bug or missing feature in the implementation? Or is it me doing something I'm not supposed to do?

[MylesBorins]

@marcofranssen do you still have the same problem if you stop using the esm module and switch to using the built in --experimental-modules on Node.js 12.x? The implementation is keeping track with 13, with a big update coming next week in 12.16.2

We are aiming to unflag ESM in 12.x in 12.17.0 which is scheduled to come out May 26th

[marcofranssen]

@MylesBorins Do you mean by unflag ESM means the experimental flag shouldn't be required anymore?

[MylesBorins]

@marcofranssen the flag is currently requried but we plan to remove the need for the flag in 12.17.0

[marcofranssen]

That results in the following when loading for example a package.json via import.

node:22538) ExperimentalWarning: The ESM module loader is experimental.
internal/modules/run_main.js:57
    internalBinding('errors').triggerUncaughtException(
                              ^

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".json" for /Users/marco/code/my-project/package.json
    at Loader.defaultGetFormat [as _getFormat] (internal/modules/esm/get_format.js:71:15)
    at Loader.resolve (internal/modules/esm/loader.js:98:42)
    at async Loader.getModuleJob (internal/modules/esm/loader.js:188:29)
    at async ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:44:17) {
  code: 'ERR_UNKNOWN_FILE_EXTENSION'
}

See here an example of what I'm using.

#!/bin/sh
':' //# http://sambal.org/?p=1014 ; exec /usr/bin/env node --experimental-modules "$0" "$@"

'use strict'

import program from 'commander'
import pkg from '../package.json'

program
  .version(pkg.version)
  .description(pkg.description)
  .parse(process.argv)

When using with esm like this it works just fine as long my package.json doesn't include "type": "module"

#!/bin/sh
':' //# http://sambal.org/?p=1014 ; exec /usr/bin/env node -r esm "$0" "$@"

import program from 'commander'
import pkg from '../package.json'

program
  .version(pkg.version)
  .description(pkg.description)
  .parse(process.argv)

we run this app via

my-project/bin/my-proj

[MylesBorins]

@marcofranssen our loader does not support loading JSON by default. It is an experimental feature which can be enabled with --experimental-json-modules

[MylesBorins]

Another possibility is to make your own require function inside of your module and use that to require JSON

import { createRequire } from 'module';

const require = createRequire(import.meta.url);
const pkg = require('./package.json');

[MylesBorins]

I'm going to close this issue as there isn't a problem in Node.js core. Please feel free to continue the discussion though

[marcofranssen]

@MylesBorins when will the experimental-json-modules become default? Also in 12.17.0?

[MylesBorins]

The current experimental json modules are unlikely to be unflagged. We are working at tc39 to try and find a way for ESM json modules to be implemented that could be supported by both node and the browser. The current implantation could not work for browsers due to security concerns. The module attributes proposal is currently the best chance we have at a standard way to.load json modules

…

On Tue, Apr 14, 2020, 7:38 AM Marco Franssen ***@***.***> wrote: @MylesBorins <https://github.com/MylesBorins> when will the experimental-json-modules become default? Also in 12.17.0? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#32613 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADZYVYW3PQF4ZFZ5U7OVWTRMRDMLANCNFSM4L2DZ55A> .