Tests: use ES modules

[marcofugaro]

Related issue: Fixes #23304

Description

While we're at it, let's update the tests to use es modules introduced in Node 16.
No need to use rollup in tests anymore.

Following the Node.js docs, the new package.json looks like this:

"type": "module",
"main": "./build/three.js",
"module": "./build/three.module.js",
"exports": {
  ".": {
    "import": "./build/three.module.js",
    "require": "./build/three.js"
  },
  "./examples/jsm/*": "./examples/jsm/*.js",
  "./src/*": "./src/*.js"
},

Note that I had to include the src folder in the exports field as well, since the tests are importing from the src folder.

I also added the .js extension to imports since in esmodules (both web and node), the extension has to be explicit.

You can test this PR by:

1. make sure you have Node 16 or greater
2. npm i --prefix test
3. npm run test-unit
4. npm run test-unit-examples

To test the browser version

1. npm i --prefix test
2. npm start
3. Open http://localhost:8080/test/unit/UnitTests.html

Note that the web tests work only in Chrome/Edge because of import maps. The import maps polyfill doesn't work with Qunit because it's syncronous.

/cc @takahirox

[mrdoob]

Nice!

Do we still need the files section?

three.js/package.json

Lines 12 to 23 in be9d017

	"files": [
	"build/three.js",
	"build/three.min.js",
	"build/three.module.js",
	"examples/js",
	"examples/jsm",
	"examples/fonts",
	"LICENSE",
	"package.json",
	"README.md",
	"src"
	],

[marcofugaro]

Do we still need the files section?

Yes 🙂 that field contains the files that are downloaded when a user installs three from npm.
The exports field indicates the files directly available for import.

[mrdoob]

What would happen if we renamed this? Say...

"./addons/*": "./examples/jsm/*.js",

Would people be able to this?

import { OrbitControls } from 'three/addons/controls/OrbitControls.js'

And, would the old version stil work?

import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls.js'

[marcofugaro]

Apparently yes, you can do that, from the docs:

And, would the old version stil work?

Only if you have both of the import aliases in the exports field:

"./addons/*": "./examples/jsm/*.js",
"./examples/jsm/*": "./examples/jsm/*.js",

Otherwise node (or any bundler) throws an error if you're trying to import something that is not in the export fields.

[mrdoob]

Excellent! That makes thing easy.

What do you think about the name addons? Do you think @drcmda will like it? 🤓

[marcofugaro]

Hahaha I don't mind the name!

I even made a three-addons package back when examples/jsm wasn't a thing 😆

[mrdoob]

Okay, I'll keep it in mind 🙏

[drcmda]

@mrdoob i do like it 😁

[mrdoob]

Thanks!