🐛 Bug: spec file starting with a number rejected

[grahamrhay]

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

passing tests

Actual

after dependabot bumped mocha from ~10.8.1 to ~11.7.6, tests started failing with this error:

npx mocha 1***.js
/app/node_modules/mocha/lib/cli/options.js:139
    throw createUnsupportedError(
    ^

Error: Option 1***.js is unsupported by the mocha cli
    at createUnsupportedError (/app/node_modules/mocha/lib/errors.js:126:13)
    at createErrorForNumericPositionalArg (/app/node_modules/mocha/lib/cli/options.js:139:11)
    at parse (/app/node_modules/mocha/lib/cli/options.js:190:5)
    at loadOptions (/app/node_modules/mocha/lib/cli/options.js:291:14)
    at Object.<anonymous> (/app/node_modules/mocha/bin/mocha.js:29:14)
    at Module._compile (node:internal/modules/cjs/loader:1781:14)
    at Object..js (node:internal/modules/cjs/loader:1913:10)
    at Module.load (node:internal/modules/cjs/loader:1505:32)
    at Function._load (node:internal/modules/cjs/loader:1309:12)
    at wrapModuleLoad (node:internal/modules/cjs/loader:254:19) {
  code: 'ERR_MOCHA_UNSUPPORTED'
}

other spec files (not starting with a number) work fine. is this a bug, or were we using something unsupported that just happened to work until now?

#5263

this, perhaps?

Minimal, Complete and Verifiable Example

create a spec in a filename starting with a number, try and run it

Versions

see above

Additional Info

No response

[official-burak]

Yeah, that's a bug. You weren't on some unsupported path.

isNumeric is !isNaN(parseFloat(input)), so parseFloat('1***.js') is 1 and mocha treats the filename as a numeric CLI token. #5263 wanted a clearer error for mocha 123, not for specs that happen to start with a digit.

The same check is still in mocha 12's parse-args.js. Making isNumeric require the whole string to be a number would keep the 123 guard and let 1foo.test.js through.