Require cycle fetch

Environment

How do you use Sentry? Sentry SaaS (sentry.io)

Which SDK and version?

"@sentry/react-native": "^3.2.13",
"@sentry/node": "^6.17.8",
"@sentry/tracing": "^6.17.8",

Steps to Reproduce

1. Install sentry and setup according to docs
2. Run app

Expected Result

No require cycle upon running the app

Actual Result

Getting a require cycle warning from sentry-react-native:

Require cycle: node_modules\react-native\Libraries\Network\fetch.js -> node_modules\whatwg-fetch\dist\fetch.umd.js -> node_modules\react-native\Libraries\Network\fetch.js

[AbhiPrasad]

We currently don’t have the cycles to investigate as we are focusing on the major JS SDK bump.

The major version does change how transports work, so let’s re-visit this after that!

[jennmueng]

Ok after further investigation here are the lines that triggers the require cycle. when the browser backend calls supportsFetch().

I assume it’s something with how React Native lazy-initializes some functionality and fetch seems to be one of them. The line calling new Headers() triggers the polyfill from whatwg-fetch to be run, which leads to the require cycle. The warning does not show if you trigger the lazy initialized fetch beforehand by adding a fetch call before

fetch("").catch((e) => {});

Also, calling new Headers() or any of the others later in the lifecycle of the app poses no issue. Which means for some reason our SDK is getting initialized very early on before the fetch polyfill I assume is eventually called by default?