Interference between Pretender and React Server Components

[thearnica]

Just want to report an issue I found during Next13 adoption - it short navigation between pages is not working.

The problem appears as TypeError: Cannot read properties of undefined (reading 'getReader') at react-server-dom-webpack-client.development.js

Root cause is at startReadingFromStream(response, r.body); with r being Response defined by pretender and .body being not defined.

In short - the underlaying polyfill does not support .body and likely will never support it - JakeChampion/fetch#1109

This basically means that the problem cannot be resolved in the downstream and might need correction at the pretender level. Why do you need FakeFetch in any case?

[bobziroll]

I'm experiencing a similar problem in React Router ≥v6.4.5. They changed their code to check the response for a body property that's not undefined. Previously, they only checked if the response was an instance of Response which passed, but pretender is returning a response with no body at all, and it's short-circuiting the navigation.