server error with nextjs , and hydration in v5

[artainjast]

Describe the bug

server error with nextjs , and hydration in v5

Your minimal, reproducible example

https://stackblitz.com/github/tanstack/query/tree/main/examples/react/nextjs-app-prefetching?embed=1&theme=light&preset=node&file=src/index.tsx

Steps to reproduce

1. it does not need any steps , it occur when you starting the app (event on dev or production mode).

Expected behavior

as a user , i don't except this error happen , and it make some conflicts with building and compiling for production

How often does this bug happen?

Every time

Screenshots or Videos

Platform

• OS : [MacOS - stackblitz]

Tanstack Query adapter

react-query

TanStack Query version

"^5.64.0" ,

TypeScript version

"5.7.2"

Additional context

No response

[TkDodo]

Thanks for filing. I’m not 100% sure what’s going on, but I debugged it a bit and the gist is that the initialPromise is passed as undefined to query.fetch here:

query/packages/query-core/src/hydration.ts

Lines 215 to 219 in bd3296b

	const initialPromise = Promise.resolve(promise).then(deserializeData)
	// this doesn't actually fetch - it just creates a retryer
	// which will re-use the passed `initialPromise`
	void query.fetch(undefined, { initialPromise })

That leads to us invoking the queryFn (because we have no promise to re-use), but the queryFn doesn’t exist yet, so it errors:

query/packages/query-core/src/retryer.ts

Line 153 in 18953be

promiseOrValue = initialPromise ?? config.fn()

When inspecting the promise we get from the server, it’s there, but initialPromise is still undefined:

@juliusmarminge does this have something to do with .then(deserializeData) ? Before that step, the promise seems to still be there. deserializeData is just our default one:

query/packages/query-core/src/hydration.ts

Lines 17 to 19 in bd3296b

	function defaultTransformerFn(data: any): any {
	return data
	}