Add T | Partial<T> to immer middleware's TS return type

[connormanning]

Related Issues or Discussions

#2491

Summary

The immer middleware adds the capability to modify the Draft<T> in a setState call in-place and not return a partial state value. But the vanilla functionality of returning a T | Partial<T>, without modifying the input state draft, is still supported and works properly.

However, the immer middleware's type definition does not currently contain the T | Partial<T> option and returns only void, which can lead to invalid code compiling cleanly but wrecking the underlying store since anything is assignable to void (see playground). This PR does not add any runtime JS functionality, but adds T | Partial<T> to the immer middleware's return type, so that if you are using immer middleware and you do return a value in a setState, that it will be type-checked.

Check List

• yarn run prettier for formatting code and docs

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Name	Status	Preview	Comments	Updated (UTC)
zustand-demo	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 19, 2024 7:34pm

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[dbritto-dev]

@connormanning let's review that in this PR #2481, thanks