Support 3rd party modules using both ESM and CommonJS

[buxxi]

The problem we had before with node-fetch migrating to an ESM got me thinking about what it would require to make 3rd party modules ESM. So I made this to test having the node_helper being either CommonJS or ESM.

If naming the file node_helper.mjs instead of node_helper.js it should load it as ESM instead.

This is just a draft, there are a few things left:

• the module alias for node_helper isn't working, the module needs to specify the file with import NodeHelper from "../../js/node_helper.js"; which is annoying
• I haven't done anything about the client side loading, but should be possible with <script type="module".../>, probably a bit harder to have the dual support of .mjs and .js without any configuration...

[rejas]

Thanks for the brainstorming first of all.

But reading "the module alias for node_helper isn't working, the module needs to specify the file with import NodeHelper from "../../js/node_helper.js"; which is annoying" is a little understatement :-) Its quite impossible to get modules to use a new syntax without leaving a lot of old ones behind (and users possibly angry)

Using a more modern syntax is probably the way to go but maybe we need to make small steps (like your async work which looks like some stuff I try out too in my branches).

[buxxi]

Could move most of the async stuff out to a separate PR to make the original intent smaller and possibly ignore my second point for now and only make this about the node_helpers. require() is sync which can only load CommonJS, import() is async which can load both, that's why I started with it and just felt the flow of continuing :)

This wasn't intended to break any of the existing modules (CommonJS modules should still load fine) and doing ESM modules will always be a bit different (no require(), import()/export(), no _dirname etc). I can't see node dropping CommonJS support without going the way of Python 2 & 3 and splitting up the community. The point is mainly about new modules and not the existing ones (sure I will migrate my own 3rd party modules). A JS developer coming from the frontend is probably already using ESM modules, Node documentation gives examples with import() and not require().

And I agree that the relative path is not an ok solution, just what I had to do for my test to actually work (as this is only a draft).

Will have to figure out why the tests segmentation faults too :)

[buxxi]

Since I failed to solve the prerequisite PR #2962 I will close this for now.