Allow using --enable-source-maps together with custom Error.prepareStackTrace

[nicolo-ribaudo]

What is the problem this feature will solve?

Some libraries use Error.prepareStackTrace to make their errors more user-friendly. One example is Babel: when we throw an error due to user configs, we hide most of our internal stack frames to that our users can more easily find where they originally called Babel.

To make sure that our implementation works well together with other libraries that use Error.prepareStackTrace, we do something like this:

const { prepareStackTrace = defaultPrepareStackTrace } = Error;

Error.prepareStackTrace = function (error, frames) {
  updateTheFrames(frames);
  // Call the original stack trace formatter
  return prepareStackTrace(error, frames);
};

As the default defaultPrepareStackTrace we use the following, which matches Node.js' default behavior:

function defaultPrepareStackTrace(err: Error, trace: CallSite[]) {
  if (trace.length === 0) return ErrorToString(err);
  return `${ErrorToString(err)}\n    at ${trace.join("\n    at ")}`;
}

I am currently using Babel together with the source-map-support package, so that errors show their original source files in the stack traces rather than the compiled ones. This works well, because source-map-support simply installs a custom Error.prepareStackTrace that then Babel's Error.prepareStackTrace will use to format the error.

A couple days ago @joyeecheung introduced me to Node.js's --enable-source-maps flag (https://nodejs.org/api/cli.html#--enable-source-maps), which basically replaces the source-map-support package. I tried to use it, but I cannot because I'm using defaultPrepareStackTrace that mimics Node.js' built-in behavior, rather than it being what Node.js does.

What is the feature you are proposing to solve the problem?

Node.js should expose its default error formatter, maybe as require("util").prepareStackTrace or as a pre-defined Error.prepareStackTrace function.

This would allow some chaining similar to how ESM loaders can compose.

What alternatives have you considered?

I'm very open to any other solution that would allow me to write an Error.prepareStackTrace that works well together with --enable-source-maps.

[legendecas]

Thanks for reporting. I believe it is worthwhile to expose the default prepareStackTrace as well, as mentioned in the OP that the mimic is not what exactly Node.js' default prepareStackTrace is doing.

Created #50827 to expose module.prepareStackTrace which supports both the default plain and source maps.

[nicolo-ribaudo]

Q: why on module?

[legendecas]

My first impression was that this could be related to other functions exposed in node:module. But as pointed out at #50827 (comment), I believe that it can be more intuitive to expose with Error.prepareStackTrace instead.