v9.0.0

[markerikson]

This major release:

• Switches to requiring React 18 and Redux Toolkit 2.0 / Redux 5.0
• Updates the packaging for better ESM/CJS compatibility and modernizes the build output
• Updates the options for dev mode checks in useSelector
• Adds a new React Server Components artifact that throws on use, to better indicate compat issues

This release has breaking changes.

This release is part of a wave of major versions of all the Redux packages: Redux Toolkit 2.0, Redux core 5.0, React-Redux 9.0, Reselect 5.0, and Redux Thunk 3.0.

For full details on all of the breaking changes and other significant changes to all of those packages, see the "Migrating to RTK 2.0 and Redux 5.0" migration guide in the Redux docs.

Note

The Redux core, Reselect, and Redux Thunk packages are included as part of Redux Toolkit, and RTK users do not need to manually upgrade them - you'll get them as part of the upgrade to RTK 2.0. (If you're not using Redux Toolkit yet, please start migrating your existing legacy Redux code to use Redux Toolkit today!)
React-Redux is a separate, package, but we expect you'll be upgrading them together.

# React-Redux
npm install react-redux
yarn add react-redux

# RTK
npm install @reduxjs/toolkit
yarn add @reduxjs/toolkit

# Standalone Redux core
npm install redux
yarn add redux

Changelog

React 18 and RTK 2 / Redux core 5 Are Required

React-Redux 7.x and 8.x worked with all versions of React that had hooks (16.8+, 17.x, 18.x). However, React-Redux v8 used React 18's new useSyncExternalStore hook. In order to maintain backwards compatibility with older React versions, we used the use-sync-external-store "shim" package that provided an official userland implementation of the useSyncExternalStore hook when used with React 16 or 17. This meant that if you were using React 18, there were a few hundred extra bytes of shim code being imported even though it wasn't needed.

For React-Redux v9, we're switching so that React 18 is now required! This both simplifies the maintenance burden on our side (fewer versions of React to test against), and also lets us drop the extra bytes because we can import useSyncExternalStore directly.

React 18 has been out for a year and a half, and other libraries like React Query are also switching to require React 18 in their next major version. This seems like a reasonable time to make that switch.

Similarly, React-Redux now depends on Redux core v5 for updated TS types (but not runtime behavior). We strongly encourage all Redux users to be using Redux Toolkit, which already includes the Redux core. Redux Toolkit 2.0 comes with Redux core 5.0 built in.

ESM/CJS Package Compatibility

The biggest theme of the Redux v5 and RTK 2.0 releases is trying to get "true" ESM package publishing compatibility in place, while still supporting CJS in the published package.

The primary build artifact is now an ESM file, dist/react-redux.mjs. Most build tools should pick this up. There's also a CJS artifact, and a second copy of the ESM file named react-redux.legacy-esm.js to support Webpack 4 (which does not recognize the exports field in package.json). There's also two special-case artifacts: an "alternate renderers" artifact that should be used for any renderer other than ReactDOM or React Native (such as the ink React CLI renderer), and a React Server Components artifact that throws when any import is used (since using hooks or context would error anyway in an RSC environment). Additionally, all of the build artifacts now live under ./dist/ in the published package.

Previous releases actually shipped separate individual transpiled source files - the build artifacts are now pre-bundled, same as the rest of the Redux libraries.

Modernized Build Output

We now publish modern JS syntax targeting ES2020, including optional chaining, object spread, and other modern syntax. If you need to

Build Tooling

We're now building the package using https://github.com/egoist/tsup. We also now include sourcemaps for the ESM and CJS artifacts.

Dropping UMD Builds

Redux has always shipped with UMD build artifacts. These are primarily meant for direct import as script tags, such as in a CodePen or a no-bundler build environment.

We've dropped those build artifacts from the published package, on the grounds that the use cases seem pretty rare today.

There's now a react-redux.browser.mjs file in the package that can be loaded from a CDN like Unpkg.

If you have strong use cases for us continuing to include UMD build artifacts, please let us know!

React Server Components Behavior

Per Mark's post "My Experience Modernizing Packages to ESM", one of the recent pain points has been the rollout of React Server Components and the limits the Next.js + React teams have added to RSCs. We see many users try to import and use React-Redux APIs in React Server Component files, then get confused why things aren't working right.

To address that, we've added a new entry point with a "react-server" condition. Every export in that file will throw an error as soon as it's called, to help catch this mistake earlier.

Dev Mode Checks Updated

In v8.1.0, we updated useSelector to accept an options object containing options to check for selectors that always calculate new values, or that always return the root state.

We've renamed the noopCheck option to identityFunctionCheck for clarity. We've also changed the structure of the options object to be:

export type DevModeCheckFrequency = 'never' | 'once' | 'always'

export interface UseSelectorOptions<Selected = unknown> {
  equalityFn?: EqualityFn<Selected>
  devModeChecks?: {
    stabilityCheck?: DevModeCheckFrequency
    identityFunctionCheck?: DevModeCheckFrequency
  }
}

hoist-non-react-statics and react-is Deps Inlined

Higher Order Components have been discouraged in the React ecosystem over the last few years. However, we still include the connect API. It's now in maintenance mode and not in active development.

As described in the React legacy docs on HOCs, one quirk of HOCs is needing to copy over static methods to the wrapper component. The hoist-non-react-statics package has been the standard tool to do that.

We've inlined a copy of hoist-non-react-statics and removed the package dep, and confirmed that this improves tree-shaking.

We've also done the same with the react-is package as well, which was also only used by connect.

This should have no user-facing effects.

TypeScript Support

We've dropped support for TS 4.6 and earlier, and our support matrix is now TS 4.7+.

What's Changed

• Update packaging, build config, and entry points for v9 by @markerikson in Update packaging, build config, and entry points for v9 #2038
• Add stack to dev mode checks by @EskiMojo14 in Add stack to dev mode checks #2064
• add an extra entrypoint for React Server Components by @phryneas in add an extra entrypoint for React Server Components #2062
• Inline hoist-non-react-statics to eliminate a dep and help shaking by @markerikson in Inline hoist-non-react-statics to eliminate a dep and help shaking #2066
• Make context typing more accurate by @EskiMojo14 in Make context typing more accurate #2041
• Fix uSES imports and run against RTK CI examples by @markerikson in Fix uSES imports and run against RTK CI examples #2070
• Copy CI setup for RTK examples by @markerikson in Copy CI setup for RTK examples #2072
• Fix useSelector() in combination with lazy loaded components breaks with react v18 (useSelector() in combination with lazy loaded components breaks with react v18 #1977) by @jeroenpx in Fix useSelector() in combination with lazy loaded components breaks with react v18 (#1977) #2068
• Actually add sideEffects: "false" to package.json in v9 by @markerikson in Actually add sideEffects: "false" to package.json in v9 #2079
• Inline react-is utils to fix tree-shaking in 9.0 by @markerikson in Inline react-is utils to fix tree-shaking in 9.0 #2085
• Rename noopCheck to identityFunctionCheck by @aryaemami59 in Rename noopCheck to identityFunctionCheck #2091
• Use scoped JSX for React types by @markerikson in Use scoped JSX for React types #2092

Full Changelog: v8.1.2...v9.0.0

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This discussion was created from the release v9.0.0.

[jjcfatras]

@markerikson for version 9 using typescript do we still need to install @types/react-redux? Here https://react-redux.js.org/tutorials/typescript-quick-start it says that as of version 8 react-redux includes its own types, but here https://redux-toolkit.js.org/tutorials/typescript#introduction we're told to install @types/react-redux.

[markerikson]

Ah, we updated that docs page for the other sites, but missed this one.

As of React-Redux v8, the codebase itself was converted to TS, so we ship our own types now - you only need @types/react-redux for v7 and earlier.

[jjcfatras]

@markerikson Thank you for the confirmation.