🐛 Bug: .mocharc.js / .mocharc.mjs / ESM export default configs don't seem to work

[codegoblin]

Bug Report Checklist

• This is NOT a security, npm audit, or GitHub Advisory issue.
• I have read and agree to Mocha's Code of Conduct and Contributing Guidelines
• I have searched for related issues and issues with the faq label, but none matched my issue.
• I have 'smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, my usage of Mocha, or Mocha itself.
• I want to provide a PR to resolve this

Expected

Given the explanation in the configuring mocha guide, I would expect a config file named .mocharc.js or .mocharc.mjs with the following contents to work:

console.log('mocha config');

export default {
  "extension": ["ts", "tsx"],
  "node-option": ["import=tsx"],
  "recursive": true,
  "reporter": "spec",
  "require": ["./test/setup.ts"],
  "spec": ["src/**/*.test.ts"],
  "timeout": 5000,
  "watch-files": ["src/**/*.ts", "test/**/*.ts"]
}

in package:

"type": "module",
...
"test": "cross-env NODE_ENV=test mocha",

Actual

When I run pnpm run test, the .mjs file is completely ignored, and the .js file is read (console output happens), but the export default { ... } seems to be ignored. Converting this config back to .mocharc.json works as expected.

Minimal, Complete and Verifiable Example

create a .mocharc.js config file with export default { ... } as the config interface and run the test suite. Config will be ignored.

Versions

version 11.7.5

Additional Info

No response

[mark-wiemer]

For reference, https://mochajs.org/running/configuring/ mentions:

JavaScript: Create a .mocharc.js (or .mocharc.cjs when using "type"="module" in your package.json) in your project’s root directory, and export an object (module.exports = {/* ... /}) containing your configuration. For native ESM and using type="module" or using .mjs, use a default export (export default {/ ... */}).

I'll try to repro this later today :)

[mark-wiemer]

@codegoblin thanks for the report, I'm only able to fully repro the issue with .mjs on 11.7.5. On main branch, the issue does not repro, and with .js on 11.7.5 things seem to work as expected. That said, I'm not sure if there are other parts of your project that may be relevant, can you try to create a small and complete repro, including the related setup files so that I have everything I need to get tests passing on my local machine? You can see my repro above for my log output: https://github.com/mark-wiemer/hello-hello/tree/d6b3d237b3fb60f418a42d885bf97cfcfb0d541f/packages/mocha/packages/repro

[mark-wiemer]

Ah, the issue here is that in Mocha 11.7.5, export default ... was getting evaluated into a property in our config object named default instead of actually going into the root object. Mocha 11.7.5 also just doesn't read .mocharc.mjs files for some reason. Both issues have been fixed in a recent commit and will definitely be fixed in 12.0.0 and are already fixed in the latest betas. Closing as completed :)