The ExtraErrorData integration is not capturing nested error causes

[michaelschufi]

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/nextjs

SDK Version

8.51.0

Framework Version

Next 15.1.3

Link to Sentry event

https://sally-and-friends.sentry.io/issues/6215894150/events/2b86efb54ff54674bac3bd0582bc1952/

Reproduction Example/SDK Setup

// sentry.server.config (same for the other two)

Sentry.init({
  integrations: [
    Sentry.extraErrorDataIntegration({
      depth: 15,
    }),
  ],
  normalizeDepth: 15,
});

// my custom error class' toJSON

export class CustomError extends Error {
  // ... tell me if you need the whole class. But the point is, that this.cause is returned inside `toJSON`

  toJSON(): Record<string, unknown> {
    return {
      message: this.message,
      name: this.name,
      cause: this.cause,
    };
  }
}

Steps to Reproduce

1. Set up a custom error class that has a toJSON method, which includes the this.cause property.
2. Throw an error which has such error in its cause. E.g.

   throw new TRPCError("Top-level error", {
     cause: new CustomError("Nested error", {
       foo: "bar"
     })
   })

Expected Result

The top-level error is getting serialized, including the extra error data.
The cause field is another structured error data. E.g.

{
  message: "Nested error",
  name: "Custom Error",
  cause: {foo: "bar"},
}

because capturing the cause is enabled by default.

Actual Result

The nested error getting serialized in the format `${errorClassName}: ${message} instead of the whole structured data.

[andreiborza]

Hi @michaelschufi, thanks for filing this.

I just tested this out and had a look at our code, indeed if cause is an Error or if a value of a property inside the JSON returned from toJSON is an Error it gets immediately serialized via toString regardless of having a toJSON itself.

This is something we can consider changing, I'll bring it up with the team. Otherwise, we also welcome contributions if you're interested.