An online and local tool to lint packaging errros and ensure compatibility across different environments. With the migration from CJS to ESM and dual browser-node support, packages are often built for a specific enviroment only and isn't future compatible as new tooling comes. This tool aims to fix them by provising useful feedback and suggestions ahead of time.

How it works

The rules applied can be found on this page. Most of them require reading the package.json and published files to easily simulate what would happen when it's being used in a specific environment. The tools starts by traversing package.json and validate all relevant exporting fields, like main, module, and exports, in parallel, cumulating a list of messages, and finally reporting them.

To get access to the published files is a challenge to. Online, this is done by fetching from npm and unzipping it. Locally, it uses npm-pack-list to get a list of files that will be published, so we don't over-scan a local project.

What I've learned

Most rules come from experience as they are only noted in hard-to-find sources. Listing them isn't great either, no one wants to read a long guide just to make a package. Instead, something automatic that brings actionable goals to package authors is more effective.

This project also gave first-hand experience with web workers, which is something I'm always curious of how it works in Vite. Luckily, most worked out of the box and I found new things that can be improved in Vite too.