[NextJS] Suppress instrumentation warning

[eseyfert]

Problem Statement

Hey there! 👋

We use @opentelemetry for instrumentation in our NextJS app, meaning we have no need for the built-in Sentry tracing.

I have disabled it for both the client and server config using tracesSampleRate: 0.
In the instrumentation-client.ts file, I have omitted the export const onRouterTransitionStart = Sentry.captureRouterTransitionStart; line as we have no need for it.

Now we get this warning whenever the app is built:

[@sentry/nextjs] ACTION REQUIRED: To instrument navigations, the Sentry SDK requires you to export an `onRouterTransitionStart` hook from your `instrumentation-client.(js|ts)` file. You can do so by adding `export const onRouterTransitionStart = Sentry.captureRouterTransitionStart;` to the file.

It would be great to have a mechanism to suppress this warning as it just produces noise in our case.
Thanks for taking the time to read this. 🙂

PS: If I completely misunderstood the point behind the onRouterTransitionStart = Sentry.captureRouterTransitionStart; line, I would love to know.

Solution Brainstorm

I could see a few ways to achieve this:

1. Provide a Sentry.init() setting to modify this behavior?

Sentry.init({
   suppressInstrumentationWarning: boolean
});

2. If tracesSampleRate is set to 0 in the instrumentation-client.ts file, don't print the warning?

[chargome]

Hey @eseyfert thanks for writing in! We need captureRouterTransitionStart for instrumenting client-side routing but if you provide your own setup it def makes sense to not show this warning – I'll add a flag for disabling the warning!

[mydea]

Also a side note, setting tracesSampleRate: 0 does not disable tracing! you should not set this attribute at all, instead. We should likely document this better, I added an issue here: getsentry/sentry-docs#14267

TLDR you should likely use __SENTRY_TRACING__ to fully disable tracing code: https://docs.sentry.io/platforms/javascript/guides/nextjs/configuration/tree-shaking/

[eseyfert]

Thank you so much for the quick answers and insights! 💯