typings for combine middleware

[Nikaple]

Bug Description

I'm experimenting with the new 5.0 releases and have noticed that the combine middleware lacks proper typing.

Screenshot:

Reproduction Link

https://www.typescriptlang.org/play/?#code/JYWwDg9gTgLgBAbzgYygUwIYzQZRtNOAXzgDMoIQ4AiALwFcBnGDAOwBMB6ANzeABt+GagG4AUKEixEKSgCNgrQiXKUaDZmy4hg7dvzQB3DOk7J5itKLFjzrZnEiNgMYBFZ4CcALwp0WXHx0AAoxOFkQBSVgpCcXN1YALhkAD2SABgAaOABPDOJibODGNBgASh8APjgYsPC4EpgABQhnV3dk4Lj21grvasaYx1b492IyzLqiMrKxMvFbdwcAEnYIGABhdxZLKB84NeR6EDRWGAA6AHNSgFEDE7OAIRyASXZQ8Oo1mABaOx2lFBqHM4BhGHAABIAFQAsgAZAAiwG4dzQDxg4jsK2++0Ox1OF2uMFR6Oeb2CX3W1AqYMhsMRyJJBIWq3WWzOGF25wwehu3AJcOAzFOaCgFMgimwUBAEH51CKaH5Zz61QQdW6CU86CupTwAWCZXOjRabQStXqcDScEVBPOyH4wAJAA1Jha8talRd7Y6zgBNV3jcTTBZY+DoDii5JNEwYE5SxgAHhgOTAaAgpGGpvcWrQRvockYqGAcjQlQA2ukALr7YosbAqxB1VkXZg5AznGBQNiMUjQKi+AAGne7QmwwWWCE02HOGvc5xSRDAKWyE6nudnrHOOUXKTKA6DC3D7FFXRGPRzOpgL1Y8Qw-D1Y4mmdGHiCuaJ19v97raAN8xsG4Xow+aFlAxa-keor-kAA

[dai-shi]

I think it's the same with v4. If it's not let us know.

you need to type your function's argument explicitly: https://tsplay.dev/mLVrZw

import { createStore } from "zustand/vanilla";
import { combine } from "zustand/middleware/combine";

const positionStore = createStore(
  combine({ position: { x: 0, y: 0 } }, (set) => ({
    setPosition: (position: { x: number; y: number }) => set({ position }),
  })),
);

[Nikaple]

I see. As I'm relatively new to the Zustand community, I am not very familiar with the behaviors of v4. When I was reading the combine documentation, I mistakenly believed that using combine would magically infer all the type definitions I could use. Perhaps we could add a small tip in the documentation to inform users about this? Specifically this sentence:

This is really helpful as it automatically infers types, so there’s no need for explicit type definitions.

[dai-shi]

@dbritto-dev any idea?

[dbritto-dev]

@dai-shi we can improve that part

[dbritto-dev]

btw, explicitly type definitions means you are typing the whole store and actions, but in this case actions should be type defined by the users like in @xstate/store