Missing process functions under workers should throw explicit error

[SimenB]

Is your feature request related to a problem? Please describe.
Jest calls mkdirp during its unit tests. Jest has also recently added support for worker_threads. However, when I wanted to try it out, hundreds of tests failed with TypeError: process.umask is not a function

It turn out mkdirp uses process.umask() if no mode is provided: https://github.com/substack/node-mkdirp/blob/f2003bbcffa80f8c9744579fabab1212fc84545a/index.js#L64

I've since found that this function missing in worker_threads is well documented: https://nodejs.org/api/worker_threads.html#worker_threads_class_worker

process.chdir() and process methods that set group or user ids are not available.

Describe the solution you'd like
If node could throw "process.umask is not available in worker threads" or similar it would have made my debugging way easier, rather than the function just be missing.

I'm not sure how that would play with typeof process.umask === 'function' checks people might have?

Describe alternatives you've considered
My solution was to pass 777 as mode explicitly to mkdirp, but a clearer error would have made the debugging way easier.

My use case might be a bit special since Jest reconstructs a fake process object for every single test (by inspecting the real one), so my rabbit hole before checking worker docs were probably deeper than most people in the same situation. I was also testing node 12 (where threads are unflagged), so I wasn't even aware I was running in threads at first.

[bnoordhuis]

I think the fact that it breaks feature detection means this proposal is DOA. Maybe other collaborators feel differently?

[targos]

It sounds reasonable to me to have a version of process.umask in worker threads that can only get the value and not modify it.

[SimenB]

It sounds reasonable to me to have a version of process.umask in worker threads that can only get the value and not modify it.

That'd certainly be nice! That would help in mkdirp's case, but not necessarily in other cases, such as missing process.chdir.

---

Would it be possible to get a list of missing APIs from process? Then we could throw an error in environments where we want to warn (like potentially Jest). E.g.

const { removedProcessFunctions, isMainThread } = require('worker_threads');

if (!isMainThread) {
  removedProcessFunctions.forEach(func => {
    Object.defineProperty(process, func, {
      value: () => {
        throw new Error(func + ' is not available inside a worker');
      }
    });
  });
}

Not sure how that plays with feature detection either (or how prevalent feature detection on process is)

[cjihrig]

Not sure how that plays with feature detection either (or how prevalent feature detection on process is)

It would break detection. However, since worker threads are still experimental, I think it makes sense to add worker-specific stubs that throw.

[SimenB]

Thank you! 🎉