Bug: Node doesn't resolve ESM correctly

[sheremet-va]

Describe the bug

@vue/test-utils provides module field, that is resolved by bundlers, but if I import library with native node (or vitest, that used native node module resolution), then imported module will be in cjs (/dist/vue-test-utils.cjs). Other issue is that all files have the same extension (js), which is not supported by Node (For reference: https://github.com/sheremet-va/dual-packaging).

This leads to @vue/test-utils importing cjs version of Vue in Vitest, which fails the tests (with --no-threads), because it was already required() when defining plugin.

To Reproduce

import { mount } from '@vue/test-utils'
// leads to cjs.js

Expected behavior

import { mount } from '@vue/test-utils'
// leads to esm.mjs

@vue/test-utils needs an exports field, so Node will correctly resolve paths:

  "exports": {
    ".": {
      "types": "./dist/index.d.ts",
      "import": "./dist/vue-test-utils.esm-bundler.mjs",
      "browser": "./dist/vue-test-utils.browser.js",
      "require": "./dist/vue-test-utils.cjs.js",
      "default": "./dist/vue-test-utils.cjs.js"
    }
  },

And mjs extension on esm files (will require twicking bundling process).

Related information:

• @vue/test-utils version: any
• Vue version: not relevant
• node version: not relevant
• npm (or yarn) version: not relevant

Additional context