Node is starting to ship an unflagged feature to allow you to require(...) es modules

This means a few things:

• we should be able to migrate many dual packages to esm-only
• we should be able to upgrade dependencies which have since moved to esm-only (but were pinned to keep CJS compatibility)
• we should be able to migrate faux modules (i.e. those with type: "module" that export CJS) to esm-only

Research methods

High impact packages

The npm-esm-vs-cjs repo contains data sets that can help us understand which high impact packages use ESM, and which use CJS (or both).

Libraries

We can search this list for libraries and take the following action(s):

• if a package is esm-only, find high impact consumers of older CJS versions of the package and upgrade them to use the latest ESM version
• if a package is cjs-only, migrate it to esm-only
• if a package is dual (ESM/cjs), migrate it to esm-only

The joyee TODO list

@joyeecheung has helpfully already discovered many packages which publish CJS and ESM (i.e. they are dual packages) but are listed as ESM only.

You can view the list here

This could be a good TODO list for migrating to esm-only.

Considerations

• Not all packages can move yet since they need to support versions of node from before require(esm) was possible. we should create an issue before a PR, to find out if the maintainers are in this situation

Questions

@joyeecheung do you know what the minimum node version is needed for this feature? when we open issues, we will have to ask if its ok to constrain to that version

I suspect many packages will still want older node support, but we will see