NextJS: transform is no longer being called in 0.41.3

[rburgst]

Describe the bug

After calling a server action which returns a new value, typically transform will be called to merge back the new state from the server.
However, lately (dont know which version, probably within the last 4 weeks), transform is not being called after the action has finished.

Your minimal, reproducible example

https://github.com/rburgst/tanstack-next-server-action

Steps to reproduce

1. Open http://localhost:3000 with your browser to see the result.

2. Set the age field to 12 then click Submit.

Expected behavior

the version field should be updated to 1 (from the initial value of 0).
This should happen because the transform function merges the new state from the server into the existing state.

Actual

the version field is not updated (because the transform function is not called).

How often does this bug happen?

Every time

Screenshots or Videos

No response

Platform

• OS: Mac OSX
• Browser: Chrome

TanStack Form adapter

None

TanStack Form version

0.41.3

TypeScript version

5.6.3

Additional context

Basically this is a slightly updated version as the vanilla next-js-server-actions example

[rburgst]

ok, it only started happening in 0.41.3, in 0.41.2 everything works as expected

[t-mart]

I see this behavior too with regression starting 0.41.3 and continuing in 0.41.4

[rburgst]

Its a bit hard to see what exactly broke it but I suspect it was this change: a56d353

[rburgst]

@crutchcorn can you take a look please?

[crutchcorn]

Please don't tag specific maintainers.