Is use-sync-external-store really required if you use createWithEqualityFn from zustand/traditional?

[dumbmatter]

I thought use-sync-external-store was just a polyfill for people on old versions of React, but the migration docs seem to say you need it, and I do indeed get a build error if I don't have it:

"use-sync-external-store/shim/with-selector.js" is imported by "node_modules/.pnpm/[email protected]_@[email protected][email protected]/node_modules/zustand/esm/traditional.mjs", but could not be resolved – treating it as an external dependency.

Also the docs website seems pretty flaky. Sometimes clicking links does nothing, sometimes search returns nothing, sometimes it's an error page like "Application error: a client-side exception has occurred (see the browser console for more information).". I'm using the latest version of Firefox.

[dbritto-dev]

@dumbmatter we're working on revamping docs, basically migrating away from nextjs to vitepress. zustand/traditional relies on use-sync-external-store

[dumbmatter]

Why though? Is use-sync-external-store not just a polyfill? Package description says it is.

[dbritto-dev]

@dumbmatter yes and no, use-sync-external-store supports selectors and equality functions widely used on Zustand

[Fabioni]

Thanks @dumbmatter, installing npm i use-sync-external-store fixes

Could not resolve "use-sync-external-store/shim/with-selector.js" imported by "zustand". Is it installed?

Shouldn't that be a dependency if it is needed for Zustand?

[dbritto-dev]

@Fabioni https://github.com/pmndrs/zustand/blob/main/package.json#L153

[Fabioni]

I had the error message

Could not resolve "use-sync-external-store/shim/with-selector.js" imported by "zustand". Is it installed?

and had to install npm i use-sync-external-store manually, so somehow https://github.com/pmndrs/zustand/blob/main/package.json#L153 did not work.

I am using version 5.0.1

[Fabioni]

Maybe because of this?

"use-sync-external-store": {
  "optional": true
}