[Bug] Can't import anything in pnp mode

[wojtekmaj]

• I'd be willing to implement a fix

Describe the bug

A clear and concise description of what the bug is.

To Reproduce

yarn set version latest
yarn init

+

package.json:

{
  "name": "berry-import-bug",
  "type": "module",
  "scripts": {
    "fail1": "node index.js",
    "fail2": "node --experimental-modules --es-module-specifier-resolution=node index.js",
    "fail3": "yarn node index.js",
    "fail4": "yarn node --experimental-modules --es-module-specifier-resolution=node index.js",
    "fail5": "node -r ./.pnp.cjs index.js",
    "fail6": "node -r ./.pnp.cjs --experimental-modules --es-module-specifier-resolution=node index.js"
  },
  "dependencies": {
    "lodash": "^4.17.19"
  }
}

index.js:

import lodash from 'lodash';

Running ANY of the scripts above will fail.

• 1, 3 and 5 will fall because of ERR_REQUIRE_ESM
• 2, 4 and 6 will correctly load index.js, but will fail to import lodash (or anything else for that matter):

berry-express-bug % yarn fail2
internal/modules/run_main.js:54
    internalBinding('errors').triggerUncaughtException(
                              ^

Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'lodash' imported from /berry-import-bug/index.js
Did you mean to import lodash-npm-4.17.19-fa87a8e838-ff2b7a95f0.zip/node_modules/lodash/lodash.js?
    at packageResolve (internal/modules/esm/resolve.js:594:9)
    at moduleResolve (internal/modules/esm/resolve.js:633:14)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:726:11)
    at Loader.resolve (internal/modules/esm/loader.js:82:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:226:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:51:40)
    at link (internal/modules/esm/module_job.js:50:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

Environment if relevant (please complete the following information):

• OS: [e.g. OSX, Linux, Windows, ...] macOS Big Sur
• Node version [e.g. 8.15.0, 10.15.1, ...] 14.5.0
• Yarn version [e.g. 2.0.0-rc1, ...] 2.1.1

[merceyz]

ESM support is tracked in #638

[wojtekmaj]

Then shouldn't running yarn fail in ESM with a clear message that it isn't supported?