🚀 Feature: Support running with node --frozen-intrinsics

[kevinoid]

Feature Request 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 want to provide a PR to resolve this

Overview

When node is invoked with the experimental --frozen-intrinsics flag (added in Node.js 11.12 by nodejs/node#25685) it causes mocha to exit due to an uncaught TypeError from attempting to set Error.stackTraceLimit:

/path/to/node_modules/mocha/lib/cli/cli.js:45
  Error.stackTraceLimit = Infinity; // configurable via --stack-trace-limit?
                        ^

TypeError <Object <Object <[Object: null prototype] {}>>>: Cannot assign to read only property 'stackTraceLimit' of function 'function Error() { [native code] }'
    at exports.main (/path/to/node_modules/mocha/lib/cli/cli.js:45:25)
    at Object.<anonymous> (/path/to/node_modules/mocha/bin/mocha.js:141:29)
    at Module._compile (node:internal/modules/cjs/loader:1469:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1548:10)
    at Module.load (node:internal/modules/cjs/loader:1288:32)
    at Module._load (node:internal/modules/cjs/loader:1104:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:174:12)
    at node:internal/main/run_main_module:28:49

It would be nice if mocha supported running under --frozen-intrinsics for testing code under this flag.

Suggested Solution

Wrapping

mocha/lib/cli/cli.js

Line 45 in d3b2c38

Error.stackTraceLimit = Infinity; // configurable via --stack-trace-limit?

in try-catch appears to be sufficient.

Alternatives

Not supporting running under --frozen-intrinsics? (yet)

Additional Info

No response

[JoshuaKGoldberg]

TIL about --frozen-intrinsics, what an interesting flag! Yes, this seems like a straightforward bug. Thank you!

[TG199]

Hi @JoshuaKGoldberg,

I've been looking into implementing the fix for the --frozen-intrinsics support, and I have a few clarifying questions:

Given that --frozen-intrinsics is still an experimental Node.js flag, what are your thoughts on adding support for it? Specifically:

• Do you see value in supporting an experimental feature?
• Are there specific use cases in Mocha's ecosystem that would benefit from this?

[JoshuaKGoldberg]

Do you see value in supporting an experimental feature?

Yes. An experimental feature available for users in Node.js is one they want the ecosystem to try out and give feedback on. Mocha breaking on it restricts people from trying it out.

Are there specific use cases in Mocha's ecosystem that would benefit from this?

Folks who're trying out the --frozen-intrinsics flag. Also people who work on Node.js and want Mocha to not block testers. 🙂

[TG199]

Got it!

[JoshuaKGoldberg]

🙌 Good news, I tried this again with the latest Mocha and it's no longer an issue! #5254 added a try/catch around the problematic line:

mocha/lib/cli/cli.js

Lines 43 to 47 in 945d6e3

	try {
	Error.stackTraceLimit = Infinity; // configurable via --stack-trace-limit?
	} catch (err) {
	debug('unable to set Error.stackTraceLimit = Infinity', err);
	}

I can confirm locally that running with --frozen-intrinsics on https://github.com/eslint/eslint's Mocha tests works.

Therefore: mocha>=11.0.2 should work with Node.js frozen intrinsics. If someone sees that not to be the case, please file a new issue with a full reproduction we can take a look at. Cheers! 🤎