Bug: command line reporter-options parameter doesn't override .mocharc.yml

[stalb]

Bug Report Checklist

• 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

Mocha should use the reporter-options specified on the command-line instead of the one defined in .mocharc.yml.

Actual

Mocha use the reporter-options defined in .mocharc.yml instead of the one specified on the command-line.

Minimal, Reproducible Example

1. Define a .mocharc.yml file with reporter-options:

recursive: true
reporter: xunit
reporter-options:
  - 'output=./test-reports/xunit.xml'

2. Call mocha using a different value for reporter-options:

node node_modules/mocha/bin/mocha --reporter-options output=./test-reports/xxxunit.xml

3. Verify that mocha has created ./test-reports/xunit.xml and not ./test-reports/xxxunit.xml

Versions

Debian Bookworm / Mocha version 6.2.3 / Node version v24.11.0 -> work as expected
Debian Bookworm / Mocha version 7.2.0 / Node version v24.11.0 -> work as expected
Debian Bookworm / Mocha version 7.2.0 / Node version v24.11.0 -> work as expected
Debian Bookworm / Mocha version 8.2.1 / Node version v24.11.0 -> work as expected
Debian Bookworm / Mocha version 8.3.0 / Node version v24.11.0 -> do not work as expected
Debian Bookworm / Mocha version 11.7.5 / Node version v24.11.0 -> do not work as expected

Additional Info

I have the same problem on other node versions (Debian Buster/Node 16 v16.20.2), so I guess it's mocha related.

The behavior has change between mocha@8.2.1 and mocha@8.3.0.
As I still have the same problem with mocha@11.7.5, it is in all versions since v8.3.0.

For me it looks very similar to issue: #3951

[Aniruddh-14]

Hi @tj
Could you please assign this issue to me? I’d like to work on resolving this issue.

[stalb]

@Aniruddh-14 you're welcome.

[mark-wiemer]

@Aniruddh-14 we don't assign issues, and TJ hasn't been a maintainer for a while :D you are welcome to work on any issue you see fit, we review PRs on a first-come, first-serve basis.

[mark-wiemer]

Thanks for reporting this, looks like the issue is due to Mocha not recognizing the clashing options as "clashing" and instead accepting them both, then deciding to take the first one, ref 62021a3:

$ npm run debug-test

> debug-test
> cross-env DEBUG=mocha:cli:mocha npm test


> test
> mocha my.test.js --reporter-option output=./test-reports/cli.xml

  mocha:cli:mocha loaded opts {
  _: [ 'my.test.js' ],
  'reporter-option': [
    'output=./test-reports/cli.xml',
    'output=./test-reports/config.xml'
  ],
  config: false,
  package: false,
  reporter: 'xunit',
  diff: true,
  extension: [ 'js', 'cjs', 'mjs' ],
  slow: 75,
  timeout: 2000,
  ui: 'bdd',
  'watch-ignore': [ 'node_modules', '.git' ]
} +0ms
  mocha:cli:mocha running Mocha in-process +1ms

I'll also note that the recommended spelling is reporter-option singular, but reporter-options plural is kept for backwards compatibility