v8.0.0

[markerikson]

This major version release updates useSelector, connect, and <Provider> for compatibility with React 18, rewrites the React-Redux codebase to TypeScript (obsoleting use of @types/react-redux), modernizes build output, and removes the deprecated connectAdvanced API and the pure option for connect.

npm i react-redux@latest

yarn add react-redux@latest

Overview, Compatibility, and Migration

Our public API is still the same ( <Provider>, connect and useSelector/useDispatch), but we've updated the internals to use the new useSyncExternalStore hook from React. React-Redux v8 is still compatible with all versions of React that have hooks (16.8+, 17.x, and 18.x; React Native 0.59+), and should just work out of the box.

In most cases, it's very likely that the only change you will need to make is bumping the package version to "react-redux": "^8.0".

If you are using the rarely-used connectAdvanced API, you will need to rewrite your code to avoid that, likely by using the hooks API instead. Similarly, the pure option for connect has been removed.

If you are using Typescript, React-Redux is now written in TS and includes its own types. You should remove any dependencies on @types/react-redux.

While not directly tied to React-Redux, note that the recently updated @types/react@18 major version has changed component definitions to remove having children as a prop by default. This causes errors if you have multiple copies of @types/react in your project. To fix this, tell your package manager to resolve @types/react to a single version. Details:

React issue #24304: React 18 types broken since release

Additionally, please see the React post on How to Ugprade to React 18 for details on how to migrate existing apps to correctly use React 18 and take advantage of its new features.

Changelog

React 18 Compatibility

React-Redux now requires the new useSyncExternalStore API in React 18. By default, it uses the "shim" package which backfills that API in earlier React versions, so React-Redux v8 is compatible with all React versions that have hooks (16.8+, and React Native 0.59+) as its acceptable peer dependencies.

We'd especially like to thank the React team for their extensive support and cooperation during the useSyncExternalStore development effort. They specifically designed useSyncExternalStore to support the needs and use cases of React-Redux, and we used React-Redux v8 as a testbed for how useSyncExternalStore would behave and what it needed to cover. This in turn helped ensure that useSyncExternalStore would be useful and work correctly for other libraries in the ecosystem as well.

Our performance benchmarks show parity with React-Redux v7.2.5 for both connect and useSelector, so we do not anticipate any meaningful performance regressions.

useSyncExternalStore and Bundling

The useSyncExternalStore shim is imported directly in the main entry point, so it's always included in bundles even if you're using React 18. This adds roughly 600 bytes minified to your bundle size.

If you are using React 18 and would like to avoid that extra bundle cost, React-Redux now has a new /next entry point. This exports the exact same APIs, but directly imports useSyncExternalStore from React itself, and thus avoids including the shim. You can alias "react-redux": "react-redux/next" in your bundler to use that instead.

SSR and Hydration

React 18 introduces a new hydrateRoot method for hydrating the UI on the client in Server-Side Rendering usage. As part of that, the useSyncExternalStore API requires that we pass in an alternate state value other than what's in the actual Redux store, and that alternate value will be used for the entire initial hydration render to ensure the initial rehydrated UI is an exact match for what was rendered on the server. After the hydration render is complete, React will then apply any additional changes from the store state in a follow-up render.

React-Redux v8 supports this by adding a new serverState prop for <Provider>. If you're using SSR, you should pass your serialized state to <Provider> to ensure there are no hydration mismatch errors:

import { hydrateRoot } from 'react-dom/client'
import { configureStore } from '@reduxjs/toolkit'
import { Provider } from 'react-redux'

const preloadedState = window.__PRELOADED_STATE__

const clientStore = configureStore({
  reducer: rootReducer,
  preloadedState,
})

hydrateRoot(
  document.getElementById('root'),
  <Provider store={clientStore} serverState={preloadedState}>
    <App />
  </Provider>
)

TypeScript Migration and Support

The React-Redux library source has always been written in plain JS, and the community maintained the TS typings separately as @types/react-redux.

We've (finally!) migrated the React-Redux codebase to TypeScript, using the existing typings as a starting point. This means that the @types/react-redux package is no longer needed, and you should remove that as a dependency.

Note Please ensure that any installed copies of redux and @types/react are de-duped. You are also encouraged to update to the latest versions of Redux Toolkit (1.8.1+) or Redux (4.1.2), to ensure consistency between installed types and avoid problems from types mismatches.

We've tried to maintain the same external type signatures as much as possible. If you do see any compile problems, please file issues with any apparent TS-related problems so we can review them.

The TS migration was a great collaborative effort, with many community members contributing migrated files. Thank you to everyone who helped out!

In addition to the "pre-typed" TypedUseSelectorHook, there's now also a Connect<State = unknown> type that can be used as a "pre-typed" version of connect as well.

As part of the process, we also updated the repo to use Yarn 3, copied the typetests files from DefinitelyTyped and expanded them, and improved our CI setup to test against multiple TS versions.

Removal of the DefaultRootState type

The @types/react-redux package, which has always been maintained by the community, included a DefaultRootState interface that was intended for use with TS's "module augmentation" capability. Both connect and useSelector used this as a fallback if no state generic was provided. When we migrated React-Redux to TS, we copied over all of the types from that package as a starting point.

However, the Redux team specifically considers use of a globally augmented state type to be an anti-pattern. Instead, we direct users to extract the RootState and AppDispatch types from the store setup, and create pre-typed versions of the React-Redux hooks for use in the app.

Now that React-Redux itself is written in TS, we've opted to remove the DefaultRootState type entirely. State generics now default to unknown instead.

Technically the module augmentation approach can still be done in userland, but we discourage this practice.

Modernized Build Output

We've always targeted ES5 syntax in our published build artifacts as the lowest common denominator. Even the "ES module" artifacts with import/export keywords still were compiled to ES5 syntax otherwise.

With IE11 now effectively dead and many sites no longer supporting it, we've updated our build tooling to target a more modern syntax equivalent to ES2017, which shrinks the bundle size slightly.

If you still need to support ES5-only environments, please compile your own dependencies as needed for your target environment.

Removal of Legacy APIs

We announced in 2019 that the legacy connectAdvanced API would be removed in the next major version, as it was rarely used, added internal complexity, and was also basically irrelevant with the introduction of hooks. As promised, we've removed that API.

We've also removed the pure option for connect, which forced components to re-render regardless of whether props/state had actually changed if it was set to false. This option was needed in some cases in the early days of the React ecosystem, when components sometimes relied on external mutable data sources that could change outside of rendering. Today, no one writes components that way, the option was barely used, and React 18's useSyncExternalStore strictly requires immutable updates. So, we've removed the pure flag.

Given that both of these options were almost never used, this shouldn't meaningfully affect anyone.

Changes

Due to the TS migration effort and number of contributors, this list covers just the major changes:

• Integrate TypeScript port by @markerikson in Integrate TypeScript port #1739
• Initial experimental React 18 compat prototyping by @markerikson in Initial experimental React 18 compat prototyping #1808
• Fix compatibility with React 18 strict effects by @markerikson in Fixed compatibility with React 18 strict effects #1817
• Update to latest React 18 alpha dependencies by @markerikson in Update to latest React 18 alpha dependencies #1834
• Port remaining v7 typetests and improve v8 types by @markerikson in Port remaining v7 typetests and improve v8 types #1855
• Add initial SSR support for React 18 and React-Redux v8 by @markerikson in Add initial SSR support for React 18 and React-Redux v8 #1835
• test: Adjust type tests to be compatible with React 18 typings by @eps1lon in test: Adjust type tests to be compatible with React 18 typings #1868
• Switch back to Subscription in useSelector to fix unsubscribe perf by @markerikson in Switch back to Subscription in useSelector to fix unsubscribe perf #1870
• Cleanup more code after pure removal by @Andarist in Cleanup more code after pure removal #1859
• Swap useSyncExternalStore shim behavior and update React deps by @markerikson in Swap useSyncExternalStore shim behavior and update React deps #1884
• Remove DefaultRootState type by @markerikson in Remove DefaultRootState type #1887
• Add SSR test for serverState behavior by @markerikson in Add SSR test for serverState behavior #1888
• Cleanup internal types in selectorFactory.ts by @Methuselah96 in Cleanup internal types in selectorFactory.ts #1889
• Remove ts-ignore for initMergeProps by @Methuselah96 in Remove ts-ignore for initMergeProps #1891
• fix(deps): add optional peer deps into peerDependencies by @kyletsang in fix(deps): add optional peer deps into peerDependencies #1893
• Update peer deps for v8 by @markerikson in Update peer deps for v8 #1895
• Port DT fix for dispatchProp arg in mergeProps by @markerikson in Port DT fix for dispatchProp arg in mergeProps #1897
• Update docs for v8 final by @markerikson in Update docs for v8 final #1902

v7.2.4...v8.0.0

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This discussion was created from the release v8.0.0.