Complex runtimeConfig values become `{}` inside the app

Environment

Nuxi 3.0.0-rc.12                                                                                     14:16:13
RootDir: /home/projects/nuxt-runtimeconfig-complex-objects                                           14:16:14
Nuxt project info:                                                                                   14:16:14

------------------------------
- Operating System: `Linux`
- Node Version:     `v16.14.2`
- Nuxt Version:     `3.0.0-rc.12`
- Nitro Version:    `0.6.0`
- Package Manager:  `npm@7.17.0`
- Builder:          `vite`
- User Config:      `runtimeConfig`
- Runtime Modules:  `-`
- Build Modules:    `-`
------------------------------

Reproduction

https://stackblitz.com/edit/nuxt-runtimeconfig-complex-objects?file=nuxt.config.ts,app.vue

Describe the bug

When passing a complex object into the runtime config it comes out as an empty object ({}) on the other side.

1. When passing in:

import redisDriver from 'unstorage/drivers/redis';

const driver = redisDriver();
console.log('driver should be: ', driver);

export default defineNuxtConfig({
  runtimeConfig: {
    driver,
  },
});

we get:

driver should be:  {                                                                                 14:18:56
  hasItem: [Function: hasItem],
  getItem: [Function: getItem],
  setItem: [Function: setItem],
  removeItem: [Function: removeItem],
  getKeys: [Function: getKeys],
  clear: [AsyncFunction: clear],
  dispose: [Function: dispose]
}
   

1. And then inspecting driver inside the app.vue:

<template>
  <div>Checkout the console.logs</div>
</template>

<script setup lang="ts">
if (process.server) {
  const config = useRuntimeConfig();
  console.log('driver is: ', config.driver);
}
</script>

we get:

driver is:  {}

Here, I’d expect driver is: ... to say the same thing as driver should be: ...

Additional context

This first arose in this nuxt-session PR by @Twitch0125. I could imagine that this is due to some de-/serialization happening. I checked the current runtime config docs and couldn’t find anything about this happening. If some de-/serialization prevents us from using non-primitive config values, I have some ideas for improvements:

1. document it in the runtime config docs
2. use typescript to disallow config values that will not make it through “whole”

Thanks ❤️

Logs

No response

[danielroe]

We don’t really want users to pass non-serialisable data from nuxt.config to the runtime part of the app as it blurs the boundary between configuration and runtime code.

As a module author, you can inject the nitro plugin yourself based on the user’s configuration of your module. (Or do various other things depending on your use case.) It’s difficult to say in the abstract, but feel free to drop me a line and I’ll happily assist.

[wobsoriano]

@BracketJohn we also have a Nuxt integration for next still in private because of some upcoming Request/Response changes. And yes, we did not go with passing config via nuxt.config because of serialization.

If you are interested in brining this into our monorepo, you can message https://twitter.com/balazsorban44

@danielroe is there any nitro plugin example related to this?