[Feature Request] extract `Error.cause` stacks when logging errors

[gioragutt]

Now that Error.cause is somewhat standard, it's be great if the cause chain's stack traces would also be extracted when logging errors, sort of like the default .toString() of exceptions in Java.

From what I could gather in the code, only err.stack is extracted.

Looking at recent NodeJS docs, it does look like the internal formatter/inspector already handles the cause of an error when printing it.

[cosieLq]

This feature would be very handy. What's the progress about it? I'd like to implement it. Maybe integrate the cause into the field stack_trace. Would it be also a useful feature to print out the errors field of AggregateError?

[branets-dasha]

The standard error serializer from pino-std-serializers that pino normally uses does a great job of merging causes into the error details, but ECS formatter doesn't use it. Maybe it could, under the hood?

For example,

throw new Error('Top-level', { cause: new Error('Root cause') });

gets turned into:

{
      "type": "Error",
      "message": "Top level: Root cause",
      "stack": "
          Error: Top level
              at <...>
          caused by: Error: Root cause
              at <...>"
}

What I'm currently doing is this:

import ecsFormat from '@elastic/ecs-pino-format';
import { err as errSerializer } from 'pino-std-serializers';

const pinoEcsOptions = ecsFormat({
    convertErr: false, // Will convert manually
});
 ...
// The default name where pino puts errors is "err", but ECS-compliant name is "error"
pinoEcsOptions.errorKey = 'error';
pinoEcsOptions.serializers = {
    error: (error: Error | unknown) => {
        if (!(error instanceof Error)) {
            return error;
        }

        // Merge cause(s) into error details using the standard pino serializer for errors.
        // ECS formatter doesn't do this automatically and internal error details get lost.
        const formattedError = errSerializer(error);

        // Transform into ECS shape.
        return {
            type: formattedError.type,
            message: formattedError.message,
            stack_trace: formattedError.stack,
        };
    },
};