[meta] Support ES Module natively

[tetsuharuohzeki]

After a long time to wait, finally, we would be able to use ES Module natively.
This issue tracks issues to support ES Module as 1st citizen of this package.

Tasks

1. Should we drop to support versions which does not have support ES Module?
2. Set "type": "module" to package.json.
3. Remove .js or .mjs from option-t/esm.
4. Reconsider the structure under option-t/lib.

Related Links

• https://github.com/nodejs/modules

[tetsuharuohzeki]

• Node.js v13.2.0 unflagged --experimental-modules.
  • https://nodejs.org/dist/latest-v13.x/docs/api/esm.html
• They published Announcing core Node.js support for ECMAScript modules

[tetsuharuohzeki]

By these document, Dual CommonJS/ES module packages, which we would like to do, we need to wait more times to stabilize --experimental-conditional-exports.

[tetsuharuohzeki]

We drop .js files from esm/ by #504

[tetsuharuohzeki]

By #520, we can use import 'option-t/esm/unwrap.mjs';

[tetsuharuohzeki]

In v22, we ships to allow import .mjs.

[tetsuharuohzeki]

Interestingly, I seem Node v12.16 supports ESM features natively by backporting them.
Their backports almost have the same degree of Node.js v13.8

[tetsuharuohzeki]

Interestingly, I seem Node v12.16 supports ESM features natively by backporting them.
Their backports almost have the same degree of Node.js v13.8

By the behavior, it was jump to conclusions.

[tetsuharuohzeki]

• I seem webpack would support exports field in webpack v5 or later.
• I sent a request to support exports field by rollup plugins.

[kogai]

I'm not sure if this is an appropriate request, but could you consider adding package.json to the exports field?

For example, in the case of using serverless-plugin-monorepo.
(FYI: It is a dependencies-resolve-helper for deploying the serverless function which developed as a monorepo package)

It seems trying to resolve package.json of each npm packages when resolving dependencies of some monorepo packages.
https://github.com/Butterwire/serverless-plugin-monorepo/blob/82991befe9fd6aeaa37cebf811be4213fa590379/index.js#L59

So if some npm package has defined exports field and doesn't define package.json in exports, serverless-plugin-monorepo can’t resolve packages properly.
I think it would be the same for any other npm package that needs to read package.json.

[tetsuharuohzeki]

@kogai I filed your problem as #726

I’d like to handle this issue separately from this issue because it should be handled as the defail of this task. Feel free to open a new issue from the next time.

[tetsuharuohzeki]

webpack v5 supports Node's export fields and @rollup/plugin-node-resolve also supported it in v11.

After esbuild's stable version support it, we can start to drop lib/ compat dir.

[tetsuharuohzeki]

After esbuild's stable version support it, we can start to drop lib/ compat dir.

This moved to #808

[tetsuharuohzeki]

As a library package, we have completed to support ES Module. We close this once.