Using -r/require flag seems force CJS

Reproduction

https://github.com/rschristian/uvu-require-reproduction

Fresh WMR app, with the Preact Uvu example (somewhat) copied in. Just with a bit of an alteration to the babel config to instead use the HTM transform that WMR uses (in prod, but this one is easily installable).

Summary of problem

The issue seems to be that when using the require flag (-r) everything is interpreted to be CJS. preact-iso is shipped with "type": "module", so it’s very clearly ESM, and yet Uvu seems to try to require() it. Maybe this is user error, but it doesn’t seem like that flag should alter module resolution.

I’ve only just came across this and it’s late here so I’ll need to do more investigation (hopefully) tomorrow.

Error Message

➜  ~/Projects/foobar git:(master) ✗ yarn test
yarn run v1.22.10
$ uvu tests -r esm -r @babel/register -i setup
/home/ryun/Projects/foobar/node_modules/pirates/lib/index.js:1
Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /home/ryun/Projects/foobar/node_modules/preact-iso/router.js
require() of ES modules is not supported.
require() of /home/ryun/Projects/foobar/node_modules/preact-iso/router.js from /home/ryun/Projects/foobar/public/header.jsx is an ES module file as it is a .js file whose nearest parent package.json contains "type": "module" which defines all .js files in that package scope as ES modules.
Instead rename router.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from /home/ryun/Projects/foobar/node_modules/preact-iso/package.json.

    at Module._extensions..js (internal/modules/cjs/loader.js:1080:13)
    at Object.newLoader [as .js] (/home/ryun/Projects/foobar/node_modules/pirates/lib/index.js:104:7)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Tool Versions

Node: v14.16.0 Yarn: v1.22.10

[rschristian]

Makes sense.

I have gotten lucky and avoided manually dealing with transforms up to this point, so going through this for the first time and learning about the of troubled areas is certainly interesting

[lukeed]

Yes, -r with uvu forces CommonJS version of uvu/run. This is because require hooks are exclusively a CommonJS thing