Fetch resolves before response has been received; response is undefined

[andreasphil]

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/vue

SDK Version

8.22.0

Framework Version

Vue 3.4.35

Link to Sentry event

No response

Reproduction Example/SDK Setup

Unfortunately I don't have a reproduction, but this is our setup:

• Vue SPA with useFetch for handling network requests
• Our repository: @digitalservicebund/ris-norms
• Sentry init: main.ts
• useFetch setup: apiService.ts

(Note that I debugged useFetch and it seems to not be a useFetch issue, see Steps to Reproduce below)

Steps to Reproduce

Summary: for some long-running (a few seconds, but <10s), fetch resolves before the actual request has finished. This leads to the fetch response being undefined. Anything accessing properties of the response then crashes. Reverting to @sentry/vue v8.20.0 fixes the issue.

Example:

fetch("some-long-running-request").then((response) => {
  // Now response is sometimes undefined, so the following would lead to a TypeError:
  if (response.status === 400) {
    // ...
  }
})

Looking at the network dev tools and server logs, I can verify that the request is fulfilled successfully. However it seems that fetch resolves before the request has finished, with undefined as the value for the response.

Possibly related:

• feat(core): Adapt spans for client-side fetch to streaming responses #12723
• rewrite of fetch is not exact  #11466 (open but refers to an older version)

Expected Result

Fetch should not resolve before the request is finished, and response should not be undefined.

Actual Result

Fetch resolves before the request has finished, response is undefined, and accessing properties of the response causes errors.

[chargome]

Hey @andreasphil thanks for reaching out. The PR you mentioned should not affect your original fetch call, as we just try to clone the response and resolve it in parallel.

Does the endpoint you are calling make use of SSE?

Anyway, I'll try to verify your issue and get back to you.

[andreasphil]

@chargome Thanks for the quick reply!

Yes, it might be unrelated. I'm not familiar with the Sentry code base, just did some quick scanning of the changelogs since v8.20 to see if anything catches my attention.

We're not using SSE.

Thanks for looking into it and let me know if you need more information.

[esetnik]

We have been hit by the same issue and are rolling back to 8.20.0. It looks to be related to #12723

[chargome]

@esetnik are you also using the @sentry/vue SDK?