Add support for ESM

[jarrodek]

I upgraded my project to work as ESM. I use the esm module when running the main script, all my renderer classes are going through a custom protocol that load modules as defined in the ES spec. I am almost ready to release the app but apparently I can't perform tests because everything is crashes. So, similarly to mocha I tried to use --require esm which fixes the problem (electron-mocha uses --require-main or --require). This, however, didn't work. Then I tried a different approach which creates a a common export file just for test, where the main file is a regular Common JS file, but it employs esm module to load a ES file that has exports for the classes. this doesn't work as well. After that I don't really have more ideas how to proceed. Maybe you guys has a similar issue and can help here?

To visualize what I am trying to do.

• the test that includes the CJS file that uses esm: https://github.com/advanced-rest-client/arc-electron/blob/redesign2020/test/ElectronCookies/SessionManager.main.spec.js#L5
• this is the CJS import file https://github.com/advanced-rest-client/arc-electron/blob/redesign2020/test/module-import.js

[inukshuk]

It's not entirely clear yet how ESM is going to work in Electron, especially in the renderer process where there is a clash between Node's and Chromium's ESM loaders. I would prefer not to work on native ESM support in electron-mocha until the situation in Electron is clear.

That said, it's absolutely no problem to test apps using ESM with electron mocha if you can use a custom loader in between. I haven't used the esm module, but I've had no issues using babel to load ES modules into electron-mocha tests both in main and renderer. If esm hooks into require, similar as babel does, then it should be enough to add --require esm but your second approach should work as well. What's the error you're running into?

[jarrodek]

Hi,
Sorry for inaccuracies. I was writing the issue report after the whole day of work in the middle of night :]

More or less I have figured out how to do this. Not sure if that's the most efficient way though.

In then test file I have the following in the imports:

const { assert } = require('chai');
const { session } = require('electron');
const _require = require('esm')(module);

const { MyClass } = _require('../../src/io/MyClass.js');

This way I am able to import a class that works in the main process for unit testing. This also works for renderer classes. Types won't work this way but at least I am able to run tests again.