TypeError: options.headers.get is not a function

[aaditya-ghag-mt]

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 package are you using?

@sentry/react

SDK Version

6.13.2

Framework Version

17.0.0

Link to Sentry event

No response

Steps to Reproduce

On our react app, we're getting one error on safari browser and it's a single client specific issue. Same react app works on our end on safari browser. All our GraphQL api's are failing also all fetch api calls are failing. I spent a huge amount of time debugging the issue but wasn't able to replicate.

Error:
TypeError
options.headers.get is not a function. (In 'options.headers.get(key)', 'options.headers.get' is undefined)

The error stack is pointing out to this code

      return originalFetch.apply(global, args).then(
        (response: Response) => {
          triggerHandlers('fetch', {
            ...handlerData,
            endTimestamp: Date.now(),
            response,
          });
          return response;
        },
        (error: Error) => {
          triggerHandlers('fetch', {
            ...handlerData,
            endTimestamp: Date.now(),
            error,
          });
          // NOTE: If you are a Sentry user, and you are seeing this stack frame,
          //       it means the sentry.javascript SDK caught an error invoking your application code.
          //       This is expected behavior and NOT indicative of a bug with sentry.javascript.
          throw error;
        },
      );

This code is from transports/instrument.ts of Sentry's source code.

From what I'd debug I feel as sentry is intercepting every request so due to some polyfill issue for native fetch, can this error occur ? Any help ?

Expected Result

Should work on safari browser!

Actual Result

Not working on safari browser!

[Lms24]

Hi @aaditya-ghag-mt, thanks for writing in!

it's a single client specific issue. Same react app works on our end on safari browser

This makes me wonder if that client might be using some sort of browser extension that messes with fetch or something along these lines.

6.13.2

Have you tried updating to version 7 of the SDK? The reason I'm asking is because we don't use options.headers.get anywhere anymore in our current code base, meaning there might be a small chance that this resolves itself with an update of the SDK.

[aaditya-ghag-mt]

@Lms24, Thanks for you reply. Just Fyi on sentry portal of our company's account, the error record in Issues Table is label as

TypeError ?(safari-extension://74ACA373-1685-4CE8-BC1F-BBBB8FBC77C9/ajax.js)

TypeError @webkit-masked-url:(//hidden/))

So as you mentioned can this be related to Safari extension issue ?

[Lms24]

Seems plausible to me that this is coming from an extension. If you want, you can paste the link of an error here so that I can take a look at it (maybe the stacktrace tells us more).
What could for instance be happening is that a browser extension patches fetch or that this browser extension is also using Sentry. In the second case, we received reports before that this leads to errors.

Again, I think upgrading to v7 might also be worth a try.

[aaditya-ghag-mt]

Will definitely consider upgrading Sentry!

[Lms24]

Just to add to this, I'd recommend to take a look at our Decluttering Sentry guide in case you want to filter out such errors coming from extensions. Btw, a similar issue was being discussed in ##5875