expect NPM package unusable in browser

🐛 Bug Report

The expect NPM package is not usable in browser, although it has a browser: build-es5/index.js field.

To Reproduce

Add this to a static page:

<script src="/node_modules/expect/build-es5/index.js"></script>

It almost works, with the sole exception that the very last line fails: module.exports = expect Because there’s no global module object.

Expected behavior

Should not throw and expose a global expect object.

If you detect that there’s no module but a window instead, doing window.expect = expect makes everything work perfectly.

[SimenB]

I’ve got a branch with some of the work done, you can work off of that: https://github.com/SimenB/jest/tree/esm-export

I think it’s just a matter of fixing the tests, and you should be good to go 🙂

[SimenB]

Ah, it’s https://github.com/rollup/rollup/issues/1646 combined with https://github.com/facebook/jest/blob/d59a4d33b6aff50df3f2a307d71797a5d0e5f298/packages/expect/src/index.js#L389

Since our next release is a major, we should probably go through and remove all module.exports usage in favor of export default. It will force people using require to do .default, but hopefully it’s not too big of a deal