[worker_threads] make JS new Error() copyable across threads

[izelnakri]

node version: v11.11.0

Today I have to normalize errors to send worker thread errors back to main thread:

parentPort.postMessage({ error: normalizeError(error) })

function normalizeError(errorObject) {
  return Object.keys(errorObject)
    .reduce((result, key) => Object.assign(result, { [key] : errorObject[key] }), {});
}

[addaleax]

Hi!

One issue with this is that we’re following the HTML spec for structured cloning as far as message passing is concerned. Web specs generally don’t do breaking changes, and I think this would be a breaking change, although I’d personally love to see something like this.

(Fwiw, we have a rather complex implementation of error serialization for this reason as well.)

/cc @nodejs/workers

[amiller-gh]

Updating this thread for posterity / paper trail.

There is movement on the spec / browser side for this. Since @addaleax's comment above the MDN article now calls out that Chrome does clone native Error objects, Firefox is working to implement, Safari has a bug open here, and the whatwg is tweaking spec semantics slightly to support.

[addaleax]

Okay, I think that this can be closed then :)