Deferred values seem broken in single fetch

[lifeiscontent]

Reproduction

https://stackblitz.com/edit/remix-run-remix-obxpgddh?file=app%2Froutes%2F_index.tsx

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @remix-run/dev: * => 2.15.3 
    @remix-run/node: * => 2.15.3 
    @remix-run/react: * => 2.15.3 
    @remix-run/serve: * => 2.15.3 
    vite: ^5.1.0 => 5.4.14

Used Package Manager

npm

Expected Behavior

expect to be able to use the value from useAsyncError

Actual Behavior

never consistently returns the error value.

[brookslybrand]

You have to throw an error. In this example a string is thrown, not an error

[lifeiscontent]

@brookslybrand I also tried a Response, and that doesn't work either

[lifeiscontent]

@brookslybrand the docs also say value which means it doesn't need to be an error. https://api.reactrouter.com/v7/functions/react_router.useAsyncError.html

[lifeiscontent]

here's a similar repro of this working without single fetch:

https://stackblitz.com/edit/remix-run-remix-msywtrm6?file=app%2Froutes%2F_index.tsx,vite.config.ts (just turn on single fetch to see it behave inconsistently)

1 caveat which personally makes this API a little rough to use is not being able to have it already consume error responses or primitive values

[brookslybrand]

This seems to be a duplicate issue of react-router #12676

I'm not sure whether it was intended or not to throw arbitrary non-error values from deferred promises before single fetch.

As for sending a Response, I don't know if that's a great value to return, since the response for the data/document has already been sent. This is further data that's streaming in