[BUG] build with yarn link

[lifaon74]

Hi, I found a bug while building an application with snowpack, where one of the package is yarn link: the result file is common-js (snowpack uses common-js entry point of the package.json in this particular situation).

This result in a success build, but in an unusable application in the browser (missing module.exports and require).

Here are the steps to reproduce the bug (I created for you a demo repo to reproduce it):

Install the package locally: https://github.com/lifaon74/hello-world

cd ./hello-world/build
yarn install
npm run build
npm run link:package

Install the snowpack test env: https://github.com/lifaon74/snowpack-test

cd ./snowpack-test
npm run link:hello-world
npm run build

Here's the build result: https://github.com/lifaon74/snowpack-test/blob/main/build/_snowpack/pkg/%40lifaon/hello-world.js
(I've commit the full build there: https://github.com/lifaon74/snowpack-test/tree/main/build)

As you may see it's common-js resulting in TypeError when loading it on a browser.

The package properly exports boths cjs and mjs: https://www.skypack.dev/view/@lifaon/hello-world

When installing normally the package (yarn install instead of yarn link "@lifaon/hello-world"), the hello-world package is correctly build and the app works juste fine.

I did not test with npm link but I guess the problem will be the same.

For more precision, don't hesitate to ask for any help.

PS: this issue #429 is related, but it's not really the same problem: in my case the build in incorrect, where in 429, its related to the hot reloading.

[FredKSchott]

We just created a PR that adds support for better handling of npm linked packages, I'd love your feedback on it and hopefully it fixes your issue: #2707