Request with FormData body makes Jest hang forever about msw HOT 6 CLOSED

FWIW, the same problem exists when using a REST API. I'm using Mocha and my test won't exit if I POST using FormData.

Note: A FormData object with no fields does not cause this problem, but as soon as you add a single field, the process hangs.

Here is a simple repo using Mocha and msw 2.2.3:
https://stackblitz.com/edit/stackblitz-starters-rprzyx?file=index.js

I tested all the way back to v2.0.0 and this same behavior is present.

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To add some context, formData is part of a convention concerning the implementation of file upload through a GraphQL API : https://github.com/jaydenseric/graphql-multipart-request-spec

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Thanks for reporting this. There was a bug in Node.js v18 related to FormData but it was since fixed and should not be an issue on the latest v18.19.0. Wonder what makes this happen on Node.js v21.

It's worth noting MSW does nothing with FormData. It's likely that if something hangs, the issue is in the FormData itself. I recommend making sure you are not using any JSDOM and run a proper Node.js environment to A/B this behavior.

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Note: interestingly, doesn't hang on Vitest.

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Root cause

This appears to be a bug in Node.js. If you run this in Node, no MSW involved, the process hangs forever on cloning the Request with a FormData body:

const data = new FormData()
data.set('foo', 'ar')

const request = new Request('http://localhost', { method: 'POST', body: data })
request.clone()
console.log('cloned')

Replace the body with any other value, the request gets clone and the process exists normally.

Reproducible on:

• v18.19.0
• v20.11.0
• v21.7.1

Filed as a bug in Node.js: nodejs/node#52167. Please follow the resolution of that issue there. Thanks.

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Also this: #1843 and this nodejs/undici#2413.

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