v8.0.0 #1903
markerikson
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v8.0.0
#1903
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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 deprecatedconnectAdvanced
API and thepure
option forconnect
.Overview, Compatibility, and Migration
Our public API is still the same (
<Provider>
,connect
anduseSelector/useDispatch
), but we've updated the internals to use the newuseSyncExternalStore
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, thepure
option forconnect
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 havingchildren
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 designeduseSyncExternalStore
to support the needs and use cases of React-Redux, and we used React-Redux v8 as a testbed for howuseSyncExternalStore
would behave and what it needed to cover. This in turn helped ensure thatuseSyncExternalStore
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
anduseSelector
, so we do not anticipate any meaningful performance regressions.useSyncExternalStore
and BundlingThe
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 importsuseSyncExternalStore
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, theuseSyncExternalStore
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: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.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 aConnect<State = unknown>
type that can be used as a "pre-typed" version ofconnect
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
typeThe
@types/react-redux
package, which has always been maintained by the community, included aDefaultRootState
interface that was intended for use with TS's "module augmentation" capability. Bothconnect
anduseSelector
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
andAppDispatch
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 tounknown
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 forconnect
, which forced components to re-render regardless of whether props/state had actually changed if it was set tofalse
. 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'suseSyncExternalStore
strictly requires immutable updates. So, we've removed thepure
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:
pure
removal by @Andarist in Cleanup more code afterpure
removal #1859useSyncExternalStore
shim behavior and update React deps by @markerikson in SwapuseSyncExternalStore
shim behavior and update React deps #1884DefaultRootState
type by @markerikson in RemoveDefaultRootState
type #1887serverState
behavior by @markerikson in Add SSR test forserverState
behavior #1888peerDependencies
by @kyletsang in fix(deps): add optional peer deps intopeerDependencies
#1893dispatchProp
arg inmergeProps
by @markerikson in Port DT fix fordispatchProp
arg inmergeProps
#1897v7.2.4...v8.0.0
This discussion was created from the release v8.0.0.
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