Add Rust-based Istanbul code instrumentation

[nicholaschiang]

Describe the feature you'd like to request

I currently use babel-plugin-istanbul to instrument my code to track code coverage while testing with Cypress:

// babel.config.js
/**
 * Instruments our code (only when running tests).
 * @see {@link https://babeljs.io/docs/en/configuration#babelconfigjson}
 * @see {@link https://docs.cypress.io/guides/tooling/code-coverage.html#Instrumenting-code}
 */
module.exports = {
  presets: ['next/babel'],
  plugins: process.env.NODE_ENV !== 'production' ? ['istanbul'] : [],
};

Describe the solution you'd like

I'd really like to use the new Rust-based compiler included by default in Next.js 12, but I can't until I'm able to instrument my code with Istanbul to track code coverage while testing.

Describe alternatives you've considered

Another possible solution would Next.js providing an option to use the custom babel.config.js only while NODE_ENV=test or something similar (i.e. I can still take advantage of the faster build times with SWC while deploying to production on Vercel but still use Istanbul to track code coverage while testing on GitHub Actions).

[timneutkens]

Please use #30174 for sharing what Babel transforms are being used, that way it's all kept in a single place.

[eden-chan]

Hacky solutions found here
https://stackoverflow.com/questions/71564063/can-i-get-next-js-to-exclude-babelrc-during-build

[LarsFlieger]

One more reason to have this feature is when your code uses exclusive SWC features like @next/font (see problem). You are not able to instrument your code anymore.

[vjpr]

Try https://github.com/kwonoj/swc-plugin-coverage-instrument

[sgoodluck]

It isn't clear to me at all how that plugin is supposed to work. The documentation needs some expanding. Do you have a working example?

[alamenai]

May this feature is related to this babel plugin with swc

[mkschreder]

Having the same problem. It would seem coverage would be one of the most basic features absolutely essential to have in place, but no...

[h2oearth]

Do you have any news about this feature? I tried this plugin, but it is broken :-/ . We use SWC and babel is not an option !