Computed does not work in nested store

[p0wl90]

Reproduction

https://play.pinia.vuejs.org/#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

Steps to reproduce the bug

1. Click on "Set mainStore.nestedNumber to 42"

Expected behavior

mainStore.isNestedNumberOne is false

Actual behavior

mainStore.isNestedNumberOne is true

Additional information

• I tried various things like wrapping isNestedNumberOne in computed() in the main store but I can't get it to work and it seems like a bug to me
• There are two variations in the Pinia Playground that work as expected

[posva]

The issue is about reactivity with Vue. By doing

return {
    nestedNumber: useNested().nestedNumber,
    isNestedNumberOne: useNested().isNestedNumberOne,
    mainNumber,
    isMainNumberOne,
  };

You are reading the numbers from nestedNumber and the boolean from isNestedNumberOne. They are just values, not reactive wrappers (Ref), so they aren't reactive anymore: https://vuejs.org/guide/essentials/reactivity-fundamentals.html#limitations-of-reactive

Here is a fixed version of what you are trying to do but it duplicates the state in two stores, avoid doing that, use a computed to not duplicate the source of truth.