Updating to @sentry/sveltekit@9.2.0 changes fetch response from any to unknown

[nonameolsson]

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/sveltekit

SDK Version

9.2.0

Framework Version

SvelteKit 2.17.2

Link to Sentry event

No response

Reproduction Example/SDK Setup

No response

Steps to Reproduce

1. Update from @sentry/sveltekit 9.1.0 to 9.2.0.
2. Inspect response from an await fetch()

Expected Result

Type should stay the same any .
This is how it was in 9.1.0.

Actual Result

Type is unknown.

I'm not saying that this is totally wrong, since unknown is better to use than any. I just can't find a reason to this change, or where it took place.

[s1gr1d]

Hello and thanks for writing in!

I could reproduce that response.json() is returning a Promise<unknown> and by going through the commits and trying each version locally I could trace it back to this PR: #14672

I still need to figure out what exactly in this PR is causing this type change.

[Lms24]

@nonameolsson where are you calling fetch? In a .svelte file (i.e. using the global fetch) or in a +page.(server.)ts load function, where you use the load function's fetch?

Also, which adapter are you using/how do you build and deploy your app? Can you share your SDK setup code?

[Lms24]

Hey, @nonameolsson we found the root cause: Since #14672, we depend on @sentry/cloudflare in the @sentry/sveltekit package. When installing, this in turn pulls in @cloudflare/workers-types which has a slightly different global type definition for fetch and the Response that fetch returns. Most importantly,

declare abstract class Body { // Response inherits from Body
  // ... rest omitted for brevity
  /* [MDN Reference](https://developer.mozilla.org/docs/Web/API/Request/json) */
  json<T>(): Promise<T>;
}

Which differs from TypeScripts original Body definition:

interface Body { // Response inherits from Body
    // ...rest omitted for brevity
    /** [MDN Reference](https://developer.mozilla.org/docs/Web/API/Request/json) */
    json(): Promise<any>;
}

The problem here is that T has no default value, so if you don't explicitly declare it, it defaults to unknown. Which is different behaviour to the TS version, where it simply always returns any and doesn't allow to pass in a custom type.

However, none of this is your fault but it simply is a problem of the SDK now pulling in a type definition that it shouldn't. I think we need to fix this in @sentry/cloudflare so that we no longer declare @cloudflare/workers-types an optional dependency but an optional peer dependency. I'll open a PR and ask our Cloudflare expert to review.

Thanks for surfacing and sorry for the troubles!

[nonameolsson]

Thank you for the quick feedback and the thorough explanation! Keep up the good work!