feat: convert HTMLNano to Es Modules

[aminya]

Fixes #259

This removes all the usage of commonjs from HTMLNano replacing it with standard ES modules. The optional dependencies are now imported using dynamic imports. So, the functionality will be preserved.

All the current tests pass. I added commonjs compatibility tests to make sure nothing breaks.

The minify function returned by htmlnano is now async due to the dynamic import. posthtml should await this promise. Based on the tests, posthtml already does this, so there should not be an issue.

This change allows adoption of HTMLNano to new projects that only work with pure ES modules.

Tests passing:

Backwards compatibility tests:

[SukkaW]

I am not a fan of pure ESM package, as well as the existing community. htmlnano is still used by toolchain/bundler that uses CommonJS. Would you like to make it a dual ESM/CJS?

[aminya]

I am not a fan of pure ESM package, as well as the existing community. htmlnano is still used by toolchain/bundler that uses CommonJS. Would you like to make it a dual ESM/CJS?

If you notice, I have kept the package backwards compatible. The main entry still points to the .cjs file compiled by Babel from the ES module.

In fact, I added some commonjs compatibility tests for that:
https://github.com/aminya/htmlnano/blob/es-modules/test/htmlnano_compat.cjs

[aminya]

Could you approve the CI?

[maltsev]

Could you approve the CI?

Sure. Just did.

[aminya]

Thank you. This PR is ready. Let me know if there is anything else to be done here.

[maltsev]

@SukkaW what do you think, can it be merged now?

[aminya]

This pull request is ready, but I made some changes to the Babel plugin responsible for .cjs extension backwards compatibility, making the output more efficient.

silane/babel-plugin-replace-import-extension#9

Depending on the timing of the merges, I'll either update this PR or make a new PR to htmlnano with the improvement.
You can preview the changes on my fork on the main branch:
https://github.com/aminya/htmlnano

[aminya]

I published my fork of the Babel plugin to unblock us. Now, the dynamic imports can be processed by bundlers (e.g. for usage as an Astro plugin) and the cjs output is very efficient!

Now, my astro-htmlnano plugin finally works:
https://github.com/aminya/astro-plugins/tree/main/packages/astro-htmlnano

[maltsev]

Thanks!

@aminya I guess this could be released as a minor version or patch as it doesn't contain any backward incompatible changes?

[aminya]

Thanks!

@aminya I guess this could be released as a minor version or patch as it doesn't contain any backward incompatible changes?

You are welcome!

I'd go with a minor version as the addition is a new feature. But it should be backwards compatible.

[maltsev]

Released: https://github.com/posthtml/htmlnano/releases/tag/2.1.0