wrapGetInitialPropsWithSentry throws an exception if getInitialProps returns undefined

[Eszik]

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

7.69.0

Framework Version

React 17.0, NextJS 12.1.0

Link to Sentry event

https://ardian.sentry.io/issues/4480381245/

SDK Setup

No response

Steps to Reproduce

If a page's getInitialProps function does not return an object, but rather undefined or null, Sentry will throw an exception on that page. This is because of this piece of code in wrapGetInitialPropsWithSentry.ts :

const initialProps: {
          _sentryTraceData?: string;
          _sentryBaggage?: string;
        } = await tracedGetInitialProps.apply(thisArg, args);

        const requestTransaction = getTransactionFromRequest(req) ?? hub.getScope().getTransaction();
        if (requestTransaction) {
          initialProps._sentryTraceData = requestTransaction.toTraceparent();

          const dynamicSamplingContext = requestTransaction.getDynamicSamplingContext();
          initialProps._sentryBaggage = dynamicSamplingContextToSentryBaggageHeader(dynamicSamplingContext);
        }

        return initialProps;

The specific error is TypeError: Cannot set properties of undefined (setting '_sentryTraceData')

For context, I had a page's getInitialProps returning undefined because I only used getInitialProps to handle server-side redirections.

I don't know if this can easliy modified whilde still keeping the instrumentation, but the exception could at least be caught to not bubble up and crash the whole page.

Expected Result

Sentry doesn't throw an exception if getInitialProps returns undefined

Actual Result

Sentry throws an exception if getInitialProps returns undefined, crashing the whole page.

[AbhiPrasad]

This is what the TypeScript type being emitted say: https://github.com/vercel/next.js/blob/628a19393bea4e40af3ef73b101669e1c2fdd672/packages/next/src/shared/lib/utils.ts#L21C62-L21C74

We can try and guard around this, but we generally expect the TS types from Next.js to be respected and it can be resolved by easily adjusting your app's getInitialProps function.

I'll defer to @lforst to make the call though.

[lforst]

Thanks for raising this. I'd say if Next.js itself doesn't throw, the SDK shouldn't either. We'll guard for this.

[Eszik]

Thanks for the quick response! I'll add that the typing from nextjs is very weak, as undefined is assignable to type { }. The return value should probably be typed as some sort of Record, but as of right now returning undefined from getInitialProps compiles just fine