Node 14 ES Module: Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: xo.config.js

It seems impossible to load a JavaScript configuration when package.json contains "type": "module".

In my project, there are complex conditions that necessitates using a JavaScript (not JSON) configuration, xo.config.js. Recently I’m upgrading my project to ES Modules by adding "type": "module" in package.json.

However, xo attempts to load xo.config.js using require(), and Node.js thinks it’s a module that can only be loaded with import(), thus throwing error:

Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /home/user/project/xo.config.js
require() of ES modules is not supported.
require() of /home/user/project/xo.config.js from /home/user/project/node_modules/cosmiconfig/dist/loaders.js 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 xo.config.js to end in .cjs, change the requiring code to use import(), or remove "type": "module" from /home/user/project/package.json.

It does not matter whether xo.config.js is written as ES Module or CommonJS.

Since removing "type": "module" is not an acceptable option, I tried renaming to xo.config.cjs, but xo does not load the configuration and is using its default configuration.

package.json

{
  "private": true,
  "type": "module",
  "scripts": {
    "lint": "xo --fix"
  },
  "devDependencies": {
    "xo": "^0.30.0"
  }
}

xo.config.js or xo.config.cjs

module.exports = {
	rules: {
		'object-curly-spacing': ['error', 'always']
	}
};

[yoursunny]

cosmiconfig 7 supposedly supports the .cjs extension, but XO doesn’t

cosmiconfig default searchPlaces includes .cjs extension: https://github.com/davidtheclark/cosmiconfig/blob/18346056c9a7fdf8d7531ea5a998edfb255fc140/src/index.ts#L111-L121

XO overrides it with a list that excludes .cjs extension: https://github.com/xojs/xo/blob/7629ce0e887bce9f056eda4300602f90ce2f89bb/lib/constants.js#L118-L124

I think cosmiconfig’s intention is that XO should use packageProp: "xo" and not override searchPlaces.

[fregante]

@sindresorhus cosmiconfig 7 supposedly supports the .cjs extension, but XO doesn’t. You can see that the tests here ignored the config and therefore fail: https://github.com/sindresorhus/refined-github/pull/4002

My current solution is to just use .xo-config.json instead