integration with jest

[blumamir]

Me and @nirsky are working on otel-js integration with jest testing framework, to collect traces from unit-tests.
Opentelemetry SDK is using "require-in-the-middle" which is not compatible with jest which introduces an internal "require" implementation and JIT compilation.

I opened this issue in jest to try and find a solution:
jestjs/jest#11295

Thought to share it here as well in the hope that someone experienced with nodejs internals / patching methods might come with a good solution.

[vmarchaud]

This is interesting to know how we could do that. I also want to point out that the whole require in the middle system isn't possible with ESM modules so we might update the system to have multiple way of hooking into modules.
I searched a bit and found out an issue opened by @Flarna a while ago, so i wanted to know if you found out if it was possible to patch module for ESM @Flarna ?

[Flarna]

To my knowledge the only way to patch ESM modules is via a transform loader hook and modify the loaded source code.

see also https://dev.to/giltayar/mock-all-you-want-supporting-es-modules-in-the-testdouble-js-mocking-library-3gh1

Please note that loader hooks are still experimental. As of now there is only one hook possible and I don't think tools like OTel should eat up such a global resource.

There is a tracking issue nodejs/node#36396
Currently work on step 1 mentioned there to simplify hooks (combine transform and getsource) is ongoing in nodejs/node#37468

Even if the loader hooks are stable in a few month/years I'm not sure if using them reliable will be easy. Just think about a chain of several independent tools like Otel doing source code modifications one after the other without knowing of each other...

[blumamir]

Thanks,
Looks like jest is a monster that does so so many things under the hood.
I will currently let go of trying to crack this integration as it is taking too much time and looks very complicated.

If someone finds a good way to do this integration, I'll be happy to help and be involved.