feat(commonjs): Expose cjs detection and support offline caching

[lukastaegert]

Rollup Plugin Name: commonjs

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

If yes, then include "BREAKING CHANGES:" in the first commit message body, followed by a description of what is breaking.

List any relevant issue numbers:

Description

Note: This features relies on the yet-to-be-released rollup/rollup#3813, specifically the new moduleParsed hook. Once that is released and the peer dependency version of this plugin has been adjusted, tests should be green and this PR will be ready for merge.

This will expose the result of the CommonJS file-type detection as a module meta property, exposed via this.getModuleInfo(id).meta.commonjs.isCommonJS or the module info passed to the moduleParsed hook.

This will for the first time allow this plugin to work with caching data taken from a disk cache that was not created in the same session. Previously in such a setup, Rollup would hang as the file type detection promises would never resolve. Now you can do this and it will work:

const { readFileSync, writeFileSync } = require('sander');
const rollup = require('rollup');
const cjs = require('@rollup/plugin-commonjs');

rollup
  .rollup({
    input: 'src/main',
    cache: getCache(),
    plugins: [cjs()]
  })
  .then(bundle => {
    storeCache(bundle.cache);
    return bundle.write({
      format: 'es',
      dir: 'dist'
    });
  });

function getCache() {
  try {
    return JSON.parse(readFileSync(__dirname, 'cache.json'));
  } catch (e) {
    return null;
  }
}

function storeCache(cache) {
  try {
    writeFileSync(__dirname, 'cache.json', JSON.stringify(cache));
  } catch (e) {
    console.log('Could not store cache', e);
  }
}

Depending on this, I seriously consider adding some built-in disk-cache capabilities into rollup-cli now (probably via a small detour across zlib to save disk space).

[lukastaegert]

cc @underfin

[lukastaegert]

As the relevant Rollup version has been released, this is now ready for review! Note that this is a breaking change as it raises the peerDependency version of Rollup.

[LarsDenBakker]

LGTM!

[shellscape]

@lukastaegert a recent merged caused a few conflicts. Please take a peek

[lukastaegert]

Done. Also made sure to add the BREAKING CHANGES marker to the first commit.