DataCloneError: The object cannot be cloned in Safari v17 (using fetch-based MSW)

[thepassle]

Prerequisites

• I confirm my issue is not in the opened issues
• I confirm the Frequently Asked Questions didn't contain the answer to my issue

Environment check

• I'm using the latest msw version
• I'm using Node.js version 14 or higher

Browsers

Safari

Reproduction repository

https://github.com/thepassle/msw-safari-repro

Reproduction steps

• npm i
• npm start
• open browser in safari 17

Current behavior

Expected behavior

No error and the object is cloned successfully

[thepassle]

Managed to hunt it down to this code:

It seems like its not possible anymore in Safari 17 to postmessage a ReadableStream. both transfer and data.body are ReadableStreams. When I set those values to something else it does work. So it looks like postMessage in combination with ReadableStream is broken.

Im not really sure this is a MSW bug, it kind of seems like a safari bug?

[thepassle]

Created an issue on webkit: https://bugs.webkit.org/show_bug.cgi?id=262531

[kettanaito]

Thanks for looking into it, @thepassle! I will close this until it's proved to be specific to MSW. So far, it looks like a Safari issue.