disallow non-JSON-serialisable types in options.runtimeConfig

[msdsk]

Environment

• Operating System: Linux
• Node Version: v17.2.0
• Nuxt Version: 3.0.0-rc.3
• Package Manager: npm@8.1.4
• Builder: vite
• User Config: -
• Runtime Modules: -
• Build Modules: -

Reproduction

in nuxt.config.ts add:

...
  runtimeConfig: {
    public: {
      someMap: new Map()
    }
  },
...

Describe the bug

The map is transformed into an empty object (regardless if the map was empty or not) instead of being passed to the browser as-is.

Additional context

The expected behavior was working in rc1

Logs

No response

[wobsoriano]

This feature would really be great. I think module options don't accept Map as well.

[danielroe]

Runtime config set in Nuxt config needs to be serialisable. Map is not a valid type for it, and no matter what, won't be passed directly to the browser. It's possible we could accept Map as a type for it in nuxt.config but I think the benefit is very slight, when you could simply do:

runtimeConfig: Object.fromEntries(config.entries())

[danielroe]

We might be able to do some interesting things with serialising different data types between server -> client (e.g. #12831, #19205) but I think that we should not support them between nuxt.config -> build. Rather, we should update the types for runtimeConfig and appConfig input in nuxt.config to disallow non-JSON-serialisable types from being set as an early-warning flag for users.