Parcel 2 JS API: Node.js ES Modules support

[ai]

🐛 bug report

@parcel/core exports an object with { default, … } instead of native ESM.

🎛 Configuration (.babelrc, package.json, cli command)

import Parcel from '@parcel/core'

let bundler = new Parcel({
  entries: join(SRC, 'index.pug'),
  defaultConfig: {
    ...defaultConfigContents,
    filePath: join(ROOT, 'node_modules', '@parcel', 'config-default')
  }
})

🤔 Expected Behavior

Parcel is a class.

😯 Current Behavior

Parcel is:

{
  registerSerializableClass: [Getter],
  unregisterSerializableClass: [Getter],
  prepareForSerialization: [Getter],
  restoreDeserializedObject: [Getter],
  serialize: [Getter],
  deserialize: [Getter],
  default: [Getter],
  BuildError: [Getter],
  createWorkerFarm: [Getter],
  INTERNAL_RESOLVE: [Getter],
  INTERNAL_TRANSFORM: [Getter]
}

Error:

TypeError: Parcel is not a constructor

💁 Possible Solution

Use conditional exports

🌍 Your Environment

Software	Version(s)
Parcel	2.0.0-nightly.420
Node	14.13.1
npm/Yarn	1.22.10
Operating System	Fedora 32

[mischnic]

Good idea.

We forgot to update the docs after a recent PR: parcel-bundler/website#731
This is the current API (and what works at the moment):

import ParcelCore from "@parcel/core";
const { default: Parcel } = ParcelCore; // TODO

import path from "path";
import { createRequire } from "module";
import { dirname } from "path";
import { fileURLToPath } from "url";

let bundler = new Parcel({
	entries: path.join(dirname(fileURLToPath(import.meta.url)), "index.pug"),
	defaultConfig: createRequire(import.meta.url).resolve(
		"@parcel/config-default"
	),
});

(async () => {
	await bundler.run();
})();

[devongovett]

Hmm we should do this for the "@parcel/plugin" package as well, and probably support loading plugins that are ESM. Not sure how to do that though as we currently use node's require to load all plugins. We'd need to add ESM support to the package manager.

parcel/packages/core/core/src/loadParcelPlugin.js

Lines 94 to 96 in eed8bf1

	let plugin = await packageManager.require(resolved, resolveFrom, {
	autoinstall,
	});

[mischnic]

We'd need to add ESM support to the package manager.

AFAICT, the only ways to somehow intercept/modify import calls are:

• loaders: https://nodejs.org/api/esm.html#esm_experimental_loaders
• https://nodejs.org/api/vm.html#vm_class_vm_module

[devongovett]

The api woks via esm now