ability to test / detect if a module is a CJS module (parse without the exception) about cjs-module-lexer

[nicolo-ribaudo]

Trying to parse a module is not enough. For example, you cannot know if this is an ES module or a CJS module just by parsing it, and at runtime it has two different behaviors:

console.log("is script?", this !== undefined);

[nicolo-ribaudo]

The proper way of detecting CJS vs ESM is to use these rules, which is what Node.js and the various bundlers do.

[thescientist13]

Sure, I understand a detect function would just be as limited as parse is, but it would still be nice to get the functionality of parse, but just without the Error being thrown if the lexar can't analyze it correctly. I understand there is some naivety in the approach, and my project absolutely favors users going down the ESM path, so it's mostly just for a convenience and a way to nudge people away from CommonJS in their dependency trees, (e.g. lodash vs lodash-es).

Or maybe there is a way with a combination of tools? Just trying to get it be "good enough". 😃

[thescientist13]

Ah, excellent! Thank you so much for sharing, will definitely dive head first into that then. 👀

[guybedford]

Detecting modules based on whether they use module syntax can be brittle - hence why we use type package boundaries in Node.js.