Support `.mjs` output [also a TypeScript issue]

I guess we are kind of being forced a little here but someone has to be the bigger guy here 😃

Can you please make it possible to plug into node’s new mjs ESMLoader workflow?

There is a TypeScript issue open already.

Some notes:

• must run node --experimental-modules something.mjs (yes mjs)

  No longer the case, but .mjs is always reserved for ESM.

• that --experimental-modules will go away obviously.

  It did but more --experimental-related flags still linger.

• that kicks in a new layer of loaders in node’s internals that completely do not honour conventional require hooks I know you must have hit that already.

  Support for ESM uses a new subsystem that handles all import operations.

• we can’t really force it on non-mjs, unless we get the nodejs team is willing to open things a little.

  No longer the case, now package.json supports { "type": "module" }… etc.

• TypeScript already supports “commonjs” as a module, maybe “mjs” too. But it seems they might be recommending npm install renamer -g then renamer -regex --find '\.js^' --replace '.mjs' './outDir/**/*.js' as a solid contribution to making things just work.

  Can’t speak to this because I no longer transpile from TS as much.

• not sure how well source maps work yet, but that will be a next step on everyone’s agenda.

  Not sure how well sourcemaps are handled by native ESM implementations.

• Some nonstandard ways exist to import/export in .js files (@std/esm and babel) but they are shredded into commonjs on demand.

  Native support for ESM is not as open yet.

• You can transpile inline and produce standard-compliant javascript that does not get shredded into commonjs, as long as you can name it mjs.

  See above!

• You are exceptionally positioned to make a difference here.

  And people want to help if they can (ie know where they would)

Further references:

• Good discussion points on nodejs PR to Allow runMain to be ESM #14369
• ECMAScript Modules in nodejs api docs.
• Related and recently indexed files in nodejs repo.
• ModuleWrap in internal/loader but seems to expose { ModuleWrap } = process.bindings('module_wrap') so not really internal “no-touch” but not officially supported and can break.

[cspotcode]

I recently implemented and released experimental ESM support. Feedback is being tracked in #1007. Please take it for a spin and let us know if it works.

[SMotaal]

@blakeembrey… thank you for leaving this open all this time.

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🎉

This meant a lot to me personally — thanks!

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Q Is there a roadmap for this, ie a place for others in the extended community to know where they may contribute towards this goal?