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Add initial SSR support for React 18 and React-Redux v8 #1835

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merged 4 commits into from
Dec 22, 2021

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markerikson
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@markerikson markerikson commented Nov 2, 2021

This PR:

  • Updates the context types to include a getServerState field
  • Updates Provider to accept a serverState prop, and if included, pass down a getServerState callback that returns that value
  • Updates useSelector to pass getServerState to uSES
  • Identifies areas where connect is almost definitely abusing uSES :)

I'd like to get some eyes on what I've got so far and find out if I'm headed in the right direction overall. The changes here are based on comments made by @acdlite in various React 18 Working Group discussions.

I'm also interested in example tests we can use to verify that any of these changes are working as intended - please offer suggestions or PRs!

connect's logic is screwy because we need to know if the child props are being recalculated first, so that we either trigger a re-render or go ahead and cascade the subscription notifications down the tree. As a result, my current code still has connect doing all the actual meaningful comparison work, and then abusing uSES by passing down the "child props selector" function as the getSnapshot argument to uSES. The actual call to getState still happens within connect itself.

This has at least passed all our tests so far, but now that I'm trying to figure out how to potentially take the getServerState callback and pass it to uSES, I'm pretty sure all of this is basically incorrect usage :)

This suggests there are three possibilities:

  • Some hypothetical fix that involves just shuffling pieces around and somehow it'll end up being sufficiently okay to work
  • Completely rewriting the guts of connect + the mapState/mapDispatch logic (which has been basically as-is and untouched since it was written in late 2016) in order to better accomodate the revised requirements
  • Leave connect as-is and say "look, it'll run okay, but if SSR hydration is your concern we just can't fully support that - it's too difficult. So, if you're still using connect you'll have to accept whatever fallback behavior React does here".

Paging interested parties:

@acdlite @timdorr @eps1lon @phryneas @dai-shi @Andarist

@markerikson markerikson changed the title [DRAFT] Add tentative SSR support for useSelector [DRAFT] Add partial SSR support (Provider and useSelector) Nov 2, 2021
@markerikson markerikson marked this pull request as draft November 2, 2021 03:15
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Comment on lines 617 to 607
const getServerSnapshot = didStoreComeFromContext
? contextValue.getServerState
: store.getState
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Do you plan to support server snapshots for a !didStoreComeFromContext case? I'm not interested in it myself but it would be a surprise to me that, as a user, I couldn't use this functionality when using a store prop

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Any changes in the connect file are entirely speculative at this point, because I don't know what I'm supposed to be doing here :)

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To support server snapshots here, connect would probably need to take a new serverState-option just like the Provider does. I think this is a niche use case, not sure if it warrants the complexity?

If this is not supported, passing store to connect could warn/error if serverState was passed to a Provider further up in the tree.

@@ -736,7 +745,10 @@ function connect<

try {
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q: when this can throw with useSyncExternalStore? shouldn't useSyncExternalStore be resilient to tearing etc that could make this sort of stuff throw pre-uSES?


const selectedState = useSyncExternalStoreWithSelector(
store.subscribe,
store.getState,
// TODO Need a server-side snapshot here
store.getState,
getServerState || store.getState,
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I wonder - do you maybe have a good reference for the getServerState snapshot API~? I've tried searching through WG discussions but I came empty-handed. I recall reading about this but would love to refresh myself on why this is needed with uSES and how React avoid the need for it with its primitives

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I've tried searching through WG discussions but I came empty-handed.

facebook/react#22361 might help. Note that my initial post made some false assumptions that were corrected.

I recall reading about this but would love to refresh myself on why this is needed with uSES

By the time a particular component is hydrated, the store might've already been mutated. Simplest example I encountered was something like

<MutatesStoreInAnEffect />
<ReadsStore />
<React.Suspense>
  <ReadsStore />
</React.Suspense>

Assuming no component suspends, the server would render the same value for the store in every ReadsStore. But if you hydrate this tree then the second ReadsStore might be hydrated after the effects of MutatesStoreInAnEffect are run (due to selective hydration). The first ReadsStore would hydrate fine because we still have the initial state.

So we need an API to tell React with what state the markup was rendered on the server.

how React avoid the need for it with its primitives

Not sure I understand this statement correctly but React does need getServerSnapshot in every version. It needs it even more in React 18. In React 17 you'd be safe against hydration mismatch if your store is never mutated during render. In React 18 you can even get hydration mismatches if your store is mutated in effects.

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Thank you for the link and the explanation. This is what I was roughly expecting. I didn't clearly understand how the client value is handled though, and according to Andrew, the "mismatched" component is just re-rendered on top of the hydrated component that was hydrated based on the server snapshot.

Not sure I understand this statement correctly but React does need getServerSnapshot in every version. It needs it even more in React 18. In React 17 you'd be safe against hydration mismatch if your store is never mutated during render. In React 18 you can even get hydration mismatches if your store is mutated in effects.

I'm wondering about the situation when no external store is involved. Just replace MutatesStoreInAnEffect with UpdatesStateInAnEffect and ReadsStore with ReadsPropOrContextValueThatComesFromReactState in your example. This is basically the very same situation as the described by your, but useState doesn't support any getServerSnapshot method:
https://github.com/facebook/react/blob/5cccacd131242bdea2c2fe4b33fac50d2e3132b4/packages/react-reconciler/src/ReactFiberHooks.new.js#L2592-L2594

So I wonder, how the implementation is different for both and how React can handle this better for a plain state value?

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So I wonder, how the implementation is different for both and how React can handle this better for a plain state value?

The issue includes this exact scenario (the codesandbox includes an implementation that uses context+state). How this is implemented I don't know and I'm pretty sure it's better I don't know. Though I suspect it has to do with individual fibers having an alternate or work-in-progress version (terminology might be off). But you can probably find out with the debugger and https://codesandbox.io/s/react-18-updating-store-in-an-effect-during-mount-causes-hydration-mismatch-uses-m6lwm?file=/src/index.js:1927-2103

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One thing I've learned from my past attempts at debugging React code is that I'm not that good at reasoning about such sublime code 🤣

Maybe @acdlite would be able to shed some light on this.

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The reason useState "just works" is because you can't update a component until after it has already hydrated

@@ -9,9 +9,11 @@ import { useEffect, useLayoutEffect } from 'react'
// is created synchronously, otherwise a store update may occur before the
// subscription is created and an inconsistent state may be observed

export const useIsomorphicLayoutEffect =
// Matches logic in React's `shared/ExecutionEnvironment` file
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nit: using an actual URL makes it easier for people to jump quickly to referenced files (if needed):

Suggested change
// Matches logic in React's `shared/ExecutionEnvironment` file
// Matches logic in React's `shared/ExecutionEnvironment` file
// https://github.com/facebook/react/blob/5cccacd131242bdea2c2fe4b33fac50d2e3132b4/packages/shared/ExecutionEnvironment.js#L10-L14

import { useIsomorphicLayoutEffect } from '../utils/useIsomorphicLayoutEffect'
import {
useIsomorphicLayoutEffect,
canUseDOM,
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If I see correctly this is a leftover - this actually ain't used in this file atm.

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Sort of the other way around. I made this change speculating I might need to use this in connect somehow, but I haven't made any actual code changes to connect yet - that's why this is a WIP PR.

}
}, [store])
}, [store, serverState])
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If I understand correctly the serverState should be an immutable value, used only for hydration purposes. Might be worth skipping this here? Or putting it in a ref (that would be read by getServerState) to make this more explicit? Obviously, that would break the rules of hooks but IMHO it's sometimes worth it to represent some constraints etc

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acdlite commented Nov 2, 2021

A suggestion regarding connect:

What's nice about the connect API is that because it's a component factory/higher-order component, you can fork the implementation inside the factory instead of within the component's render body. You're already taking advantage of this by, for example, conditionally wrapping the ConnectFunction component with React.memo. But it looks like most the forking happens within ConnectFunction, inside the body of the component. Because of the hook rules, this means that a single component has to pay the cost of every possible hook that you might need to satisfy all the different connect API contracts.

One thing you could do to manage the complexity of these different variants is to lift the forked behavior out of the component and into the factory, like you already do with React.memo. Something like this:

// This code is way simplified, obviously, just trying to illustrate the basic idea
function connect(mapStateToProps, mapDispatchToProps, mergeProps) {
  return Component => {
    if (mapStateToProps == null) {
      // No selector provided
      // These don't need useSyncExternalStore at all.
      if (typeof mapDispatchToProps === 'function') {
        // Custom action creators
        return connectWithNoSelectorAndCustomActionCreators(Component, mapDispatchToProps);
      } else if (mapDispatchToProps != null) {
        // Basic action creators
        const actionCreators = mapDispatchToProps;
        return connectWithNoSelectorAndBasicActionCreators(Component, actionCreators);
      } else {
        // No action creators
        return connectNoOp(Component);
      }
    } else {
      // Selector provided
      if (mergeProps === null) {
        const selector = mapStateToProps;
        if (typeof mapDispatchToProps === 'function') {
          // Custom action creators
          return connectWithCustomActionCreators(Component, selector, mapDispatchToProps);
        } else if (mapDispatchToProps != null) {
          // Basic action creators
          const actionCreators = mapDispatchToProps;
          return connectWithBasicActionCreators(Component, selector, actionCreators);
        } else {
          // No action creators
          return connectWithNoActionCreators(Component, selector);
        }
      }
    }
    // ...and so on
  }
}

Then each branch can make different implementation trade offs, instead of needing to write a single component that handles every scenario. I think this would help with managing maintenance complexity. It would also be better for performance because each connected component is only paying the cost of the hooks that it needs. So for example, a connect with no mapStateToDispatch doesn't need a useSyncExternalStore.

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@acdlite yeah, as written right now, all that logic is offloaded into the "selector"-style logic over in the connect folder itself.

That's kinda what I was saying earlier - sure, it's possible to completely refactor / rewrite all that existing logic - it's "just" code! :) Question is how much effort it would take and how much benefit there would be.

Part of me is very tempted to just say: "look, connect is still here and continues to work as-is, but it's not going to get to take advantage of the 'proper' SSR/hydration support because it's too complex for us to deal with and it's a legacy API. If you want that to work right, switch to useSelector".

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acdlite commented Nov 2, 2021

That's kinda what I was saying earlier - sure, it's possible to completely refactor / rewrite all that existing logic - it's "just" code! :) Question is how much effort it would take and how much benefit there would be.

Maybe there's a compromise where we can make it work for the "simple" cases, then fall back to the current implementation for anything more complex. That might simplify the upgrade strategy/messaging for existing apps:

  • All existing code just works
  • If you use useSelector, it also works with Concurrent React features
  • If you use connect without edge case APIs, it also works with Concurrent React features
  • If you use connect with edge case APIs, you may or may not run into subtle concurrency issues. Consider migrating to useSelector if you care about Concurrent React compatibility.

@markerikson
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From Dan, a couple React 18 SSR demos that may be good to play with:

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Nice work on this. connect is tricky indeed, but I think most of that doesn't relate to getServerSnapshot specifically, but supporting concurrency in general. 😅

To me it looks like this approach should get Redux to the first step described under "Hydrating Data" in Sebastians semi-new Library Upgrade Guide: <script> (e.g. SSR frameworks)
, that is, everything works when all state is emitted and available on the client before React hydration starts (just like today).

I think modifying Redux state with Suspense combined with streaming is where it's going to get really tricky, really fast, but also not something I'm sure Redux should support and either way a later problem. 😄

@@ -19,14 +22,15 @@ export interface ProviderProps<A extends Action = AnyAction> {
children: ReactNode
}

function Provider({ store, context, children }: ProviderProps) {
const contextValue = useMemo(() => {
function Provider({ store, context, children, serverState }: ProviderProps) {
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I started thinking about ways to solve not having to pass in serverState explicitly here, and while possible, I realized the tradeoffs are not worth it (touching the redux-package for example). I think it makes sense to pass it in! 👍

Comment on lines 617 to 607
const getServerSnapshot = didStoreComeFromContext
? contextValue.getServerState
: store.getState
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To support server snapshots here, connect would probably need to take a new serverState-option just like the Provider does. I think this is a niche use case, not sure if it warrants the complexity?

If this is not supported, passing store to connect could warn/error if serverState was passed to a Provider further up in the tree.

subscribeForReact,
// TODO This is incredibly hacky. We've already processed the store update and calculated new child props,
// TODO and we're just passing that through so it triggers a re-render for us rather than relying on `uSES`.
actualChildPropsSelector,
// TODO Need a real getServerSnapshot here
actualChildPropsSelector
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If I understand things correctly (I might very well not!), the logic for handling prop changes etc shouldn't matter for the getServerSnapshot since it's called on hydration, so I think it could be roughly (not accounting for store as a prop etc):

() => childPropsSelector(contextValue.getServerState(), wrapperProps)

Unless uSES calls this again sometime after hydration, in which case you would need to snapshot the wrapperProps so they would stay the same, but I don't think this is the case.

As to how well the actualChildPropsSelector works overall after hydration, I couldn't say, it does seem like it could lead to bugs, but I think the above would at least be the equivalent way to do it for SSR?

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Yeah, I'm totally not going to bother letting that get passed to connected components as a prop. This is too complex already as it is :) Might be able to add that warning though.

I think you may be on the right track with the childPropsSelector suggestion!

@markerikson
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@Ephem Thanks for the feedback!

Could I ask you for a favor? The biggest thing I need atm is an example project that does Redux-based SSR, and ideally in conjunction with React 18 SSR, so that I have something to play with.

Dan linked me a couple React 18 SSR projects, which I pasted into a comment just above.

Could you either point me to a couple of Redux-based SSR projects so that I can smash the two together, or if you actually have time try to set up a Redux+React 18 project so that I can use it as a testbed?

I want to try to do this set of changes the right way, but I really don't have any meaningful React/Redux SSR experience to draw from. If I try to figure out how to set up all that stuff from scratch myself it's going to take a while before I even have something that I can test against :)

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Ephem commented Dec 9, 2021

I can't promise anything, but I'll try to hook you up with something basic at least! I've just started looking into React Query's React 18 SSR-support as well, so this is heavily on my mind now and I'll see if I can come up with some tests etc as well, though personal time is never in great supply. 😅

About those two examples, I don't think Redux should actually support either right now. Looks simple enough to rip out Suspense and progressive hydration from the first one and set up the base case I think should be supported thought!


Below this is just a look at the demos and why I don't think they should be supported now. Lets classify them:

https://codesandbox.io/s/kind-sammet-j56ro?file=/src/Html.js - Streaming rendering with Suspense data fetching and progressive hydration
https://github.com/vercel/next-rsc-demo - React Server Components

Neither Suspense data fetching nor RSCs are officially supported in the React 18 release and I think both are going to be hard to support fully in Redux. I'll try to write up why in more detail at some point, but it basically boils down to Redux being a single big store where any part of the app might behave differently based on any part of the store, and on hydration/getServerSnapshot all data needs to already be there. While it can support streaming, the app can not start hydrating before Redux has a full serverState so to speak, which means it gets tricky with Suspense where the store changes during rendering.

Or if you think about this great image from Shaundais fantastic talk, it's hard to imagine how Redux could currently hydrate these slices individually. RSCs are even trickier since they also happen on page navigation etc, so it's not really just hydration anymore.

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Ephem commented Dec 9, 2021

Oh and just to clarify, I used streaming and progressive hydration a bit sloppily, what I meant is hydrating while still streaming. The reason to implement getServerSnapshot at all is to support progressive hydration after all.

Say for example you only keep app state in Redux (maybe it's just the default reducer state + some state derived from cookies or something, known before rendering), but use Suspense for code splitting, implementing getServerSnapshot will let that app progressively hydrate as long as the initial Redux state is known when that hydration starts. There are a bunch of cases/variations where this is useful (even with server data in Redux, fetched ahead of time), it's just that they rely on the state being there for Redux before hydration starts. :)

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Ephem commented Dec 9, 2021

I wanted to get it done sooner than later (had a kid-free evening! 🎉), so I threw together something very quick and dirty from that first example: https://codesandbox.io/s/gifted-monad-npltr?file=/server/render.js

It's rough, but should showcase both how progressive hydration lets us click the button at the top before comments has hydrated, and that it will currently cause a hydration-mismatch for the comments section because a store value has updated. (Tearing itself is expected here, can't update a part of the app that hasn't hydrated yet)

I think this is the case Redux should aim to support for React 18. Data is "fetched" ahead of rendering on the server, and is available before hydration starts on the client, but progressive enhancement of Suspense-based code splitting should work without hydration mismatches, even when state updates in parents.

Hope it helps, didn't have time to comment it as much as I wanted, so do ask if things are unclear. 😄

Edit: I updated the sandbox slightly, so might not match the description above exactly, but still shows the same things.

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Sweet, thank you! May not be able to look at this for a bit due to other priorities, but I really appreciate your expertise on Redux+SSR in general and you putting this together specifically!

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Just rebased this against the latest type changes in master.

@Ephem : could I ask you to try converting that sandbox into a minimal standalone test file? I can play around with the sandbox as an actual project some (and I'll try to do that a bit now), but ultimately I'm going to want to have some kind of test that verifies this behavior works. Don't need it to pass yet :) just needs to do the equivalent store setup + rendering + hydration, and ideally fail based on React warning about hydration mismatch or something with connect, so that I can confirm that whatever changes I might make here fix the behavior.

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Well hey, early good news. I cloned the SSR example repo, added a store.dispatch(incrementCount()) on startup before initial render, and confirmed that I get a hydration warning with both 7.2.6 and 8.0.0-beta.1.

I then used yalc to add a build from this branch, updated <App> to pass through <Provider serverState={initialState}>, and confirmed that there is no hydration warning!

So that looks like useSelector works okay. Now to play around with connect and see what I can come up with...

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Aaaand....

applying @Ephem 's suggestion to connect seems to work!

        actualChildProps = useSyncExternalStore(
          subscribeForReact,
          actualChildPropsSelector,
          // Use the server state if it's available
          getServerState
            ? () => childPropsSelector(getServerState(), wrapperProps)
            : actualChildPropsSelector

I added a second "count" button to the demo app that uses connect instead for the store state, verified that I see a hydration warning with the build from the PR, then made that change locally and verified that I do not see a hydration warning.

This really needs more extensive testing, but given that I also see I screwed up the beta by adding some things into deps instead of devDeps, I think I'm going to go ahead and merge these changes now, and put out beta.2. We can add more tests in a follow-up PR.

@markerikson markerikson marked this pull request as ready for review December 22, 2021 21:35
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told you I really needed a viable demo to compare against :)

@markerikson markerikson merged commit 2e24c19 into master Dec 22, 2021
@markerikson markerikson deleted the feature/ssr-support branch December 22, 2021 21:42
@markerikson markerikson changed the title [DRAFT] Add partial SSR support (Provider and useSelector) Add initial SSR support for React 18 and React-Redux v8 Dec 22, 2021
children: ReactNode
}

function Provider<A extends Action = AnyAction>({
store,
context,
children,
serverState,
}: ProviderProps<A>) {
const contextValue = useMemo(() => {
const subscription = createSubscription(store)
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q: this component still relies on a custom Subscription and custom notification propagation etc. Doesn't useSyncExternalStore solve the ordering issue?

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Nope, not at all. uSES still creates store subscriptions same as always, and React still runs effects bottom-to-top on mount. So, children still subscribe before parents, etc, and we still have to do work on our side to enforce the "top-down updates" requirement for connect.

The only thing in React that has ever helped with that was when we switched v6 to read state updates from context. It worked.... which is why it was so frustrating that it also turned out to be the worst case for performance updates.

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we still have to do work on our side to enforce the "top-down updates" requirement for connect.

Isn't the problem relevant to useSelector too? Is React subscribing to the "external store" (Redux) with uSES still in the order that makes shenanigans required? Is the zombie children problem still relevant with uSES? Or is the problem somewhat fixed with automatic batching and top-down rerender that should happen with it? As automatic batching should end up rerendering things in top-down order, right?

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Yes, the problem is entirely relevant to useSelector, and there's absolutely nothing we can do to fix it - because hooks can't render context providers, so we can't enforce top-down behavior. That's why I documented all the "zombie child" concepts in the hooks API page in the first place:

https://react-redux.js.org/api/hooks#stale-props-and-zombie-children

And no, batching still has nothing to do with this problem, because it's the subscription callbacks themselves that are the problem, and those run outside of React when the store is updated.

The hacky-but-valid workaround that both useSelector and uSES take is catching errors in a selector when subscribers are notified, forcing a re-render anyway, re-running the selector during the render, and seeing if it explodes again or succeeds.

That workaround is good enough that it does actually mostly mitigate the issue. But the root cause of the problem still exists - components can end up subscribing to the store in an order where a child is notified before its parent, and if the child depends on using props in its selector, those props can be stale or the child may be reading state right before its parent is about to stop rendering the child.

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Ok, I understand how automatic batching is not the remedy for the problem.

That workaround is good enough that it does actually mostly mitigate the issue. But the root cause of the problem still exists - components can end up subscribing to the store in an order where a child is notified before its parent, and if the child depends on using props in its selector, those props can be stale or the child may be reading state right before its parent is about to stop rendering the child.

I must say that I'm somewhat disappointed with the uSES API then. I was under the impression that this problem would actually be solved by this API. This problem is affecting all external stores and thus the implementation that would guard users against this problem is still very complicated - so marketing uSES as a tool solving external store problems is somewhat misleading. I think that what it solves was way easier to solve in the userland (maybe apart from allowing inline selectors, as that was super tricky) than the zombie children problem - solving this problem at the React level would be the bigger "win" for the library authors.

@acdlite is solving this problem out of the scope of uSES? How are other external stores supposed to handle those situations? Should we use the hacky solution outlined above by @markerikson?

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FWIW uSES already implements that "hacky solution" :) and specifically inspired by useSelector doing it first.

Really the problem is a mismatch in data shapes: a linear array of subscriber callbacks executed in order, vs a tree of components where A) mount effects are executed bottom-to-top, and B) components can be added and removed over time.

If there were some way to actually correlate "adding a subscriber" with "actual position in the React component tree", then it would be theoretically possible to build a smarter notification system that actually notifies subscribers in tree parent->child order. But there's no way to know where a given component is in the tree.

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If there were some way to actually correlate "adding a subscriber" with "actual position in the React component tree", then it would be theoretically possible to build a smarter notification system that actually notifies subscribers in tree parent->child order. But there's no way to know where a given component is in the tree.

I would put the asterisk here that it's no way to know that in the userland - that's why I think this is the problem worth solving in the React itself (in the uSES).

FWIW uSES already implements that "hacky solution" :) and specifically inspired by useSelector doing it first.

Hm, so I'm a little bit confused right now. I wonder if I understand the whole zombie children problem right now - I think I understand the problem but I might not understand how the problem is solved in React Redux today.

So to get us on the same page. This is what I think right now:

  1. zombie children problem is caused~ by subscriber callbacks being called "out of order" because a child's callback can be called before the parent's callback - this leads to errors being thrown when items in the store are deleted during the latest dispatch~
  2. the error is captured by React Redux and a new rerender is being scheduled
  3. that new rerender is already executed when props are already updated and thus the selector should no longer throw or a rerender for that child might not happen at all because that component could have been unmounted by the render that has thrown (unmounted by its parent rerendering with the selected state that already doesn't contain the deleted item)
  4. so in a sense - the whole zombie children problem is already "solved" by capturing errors and rerendering, the point is that users of React Redux don't have to deal with this. They might occasionally observe weird-ish things when debugging, but that's acceptable.
  5. however, there is still the cost of the child being rendered at all as that could have been prevented if subscriptions would merely mark components as "dirty" and the state would actually be selected in render - with such a solution the child's subscriber wouldn't select anything that could throw (if only this would be batched and performed in the top-down order). Or if the item wasn't completely removed and the error is caused by partial lack of information etc then we get 2 renders there instead of one.

Is this reasoning correct? I think that I see where the use-sync-external-store/shim implements the try/catch dance and that looks good. It means that libraries using that won't have to deal with this problem at all because that's covered there. I wonder though - if the implementation of the "native" useSyncExternalStore the same or is the issue mitigated there because things can actually be executed in the "correct" order in React 18?

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Yep, that's all correct. (fwiw I don't think the "cost" thing in step 5 is really a meaningful issue.)

You can see that the actual useSyncExternalStore does the same 'rerender if error" behavior here:

https://github.com/facebook/react/blob/3dc41d8a2590768a6ac906cd1f4c11ca00417eee/packages/react-reconciler/src/ReactFiberHooks.new.js#L1482-L1491

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Yep, that's all correct. (fwiw I don't think the "cost" thing in step 5 is really a meaningful issue.)

I agree that this could have been somewhat exaggerated on my side. If this is only affecting subscribers and not rerenders then I guess this is somewhat OK (I assume that the inner component might in fact not even rerender, even if it throws, if it gets "unmounted" by the parent). However, I still find it a little bit strange that React 18 doesn't try to mitigate this all together in a smarter way - but dunno, maybe the smarter way would have some perf implications for the whole thing.

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Ephem commented Dec 23, 2021

Nice work! 👏 Glad the sandbox helped and yeah, I plan to add that and more tests, though I have some other things to look at first. 😀

There might be some more nuance here, I'm still thinking and exploring, I'll get back with any findings.

github-merge-queue bot referenced this pull request in valora-inc/wallet Mar 5, 2024
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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [react-redux](https://togithub.com/reduxjs/react-redux) | [`^7.2.9` ->
`^9.1.0`](https://renovatebot.com/diffs/npm/react-redux/7.2.9/9.1.0) |
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|
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|
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|

---

### Release Notes

<details>
<summary>reduxjs/react-redux (react-redux)</summary>

###
[`v9.1.0`](https://togithub.com/reduxjs/react-redux/compare/v9.0.4...v9.1.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.4...v9.1.0)

###
[`v9.0.4`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.4)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.3...v9.0.4)

This **bugfix release** updates the React Native peer dependency to be
`>= 0.69`, to better reflect the need for React 18 compat and
(hopefully) resolve issues with the `npm` package manager throwing peer
dep errors on install.

#### What's Changed

- Allow react-native newer than 0.69 as peer dependency by
[@&#8203;R3DST0RM](https://togithub.com/R3DST0RM) in
[https://github.com/reduxjs/react-redux/pull/2107](https://togithub.com/reduxjs/react-redux/pull/2107)

**Full Changelog**:
reduxjs/react-redux@v9.0.3...v9.0.4

###
[`v9.0.3`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.3)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.2...v9.0.3)

This **bugfix release** drops the ReactDOM / React Native specific use
of render batching, as React 18 now automatically batches, and updates
the React types dependencies

#### Changelog

##### Batching Dependency Updates

React-Redux has long depended on React's `unstable_batchedUpdates` API
to help batch renders queued by Redux updates. It also re-exported that
method as a util named `batch`.

However, React 18 now auto-batches all queued renders in the same event
loop tick, so `unstable_batchedUpdates` is effectively a no-op.

Using `unstable_batchedUpdates` has always been a pain point, because
it's exported by the renderer package (ReactDOM or React Native), rather
than the core `react` package. Our prior implementation relied on having
separate `batch.ts` and `batch.native.ts` files in the codebase, and
expecting React Native's bundler to find the right transpiled file at
app build time. Now that we're pre-bundling artifacts in React-Redux v9,
that approach has become a problem.

Given that React 18 already batches by default, there's no further need
to continue using `unstable_batchedUpdates` internally, so we've removed
our use of that and simplified the internals.

We still export a `batch` method, but it's effectively a no-op that just
immediately runs the given callback, and we've marked it as
`@deprecated`.

We've also updated the build artifacts and packaging, as there's no
longer a need for an `alternate-renderers` entry point that omits
batching, or a separate artifact that imports from `"react-native"`.

#### What's Changed

- Drop renderer-specific batching behavior and deprecate `batch` by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2104](https://togithub.com/reduxjs/react-redux/pull/2104)
- Drop `@types/react-dom` and lower `@types/react` to min needed by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2105](https://togithub.com/reduxjs/react-redux/pull/2105)

**Full Changelog**:
reduxjs/react-redux@v9.0.2...v9.0.3

###
[`v9.0.2`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.2)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.1...v9.0.2)

This **bugfix release** makes additional tweaks to the React Native
artifact filename to help resolve import and bundling issues with RN
projects.

#### What's Changed

- Change react-native output extension from `.mjs` to `.js` by
[@&#8203;aryaemami59](https://togithub.com/aryaemami59) in
[https://github.com/reduxjs/react-redux/pull/2102](https://togithub.com/reduxjs/react-redux/pull/2102)

**Full Changelog**:
reduxjs/react-redux@v9.0.1...v9.0.2

###
[`v9.0.1`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.1)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.0...v9.0.1)

This **bugfix release** updates the package to include a new
`react-redux.react-native.js` bundle that specifically imports React
Native, and consolidates all of the `'react'` imports into one file to
save on bundle size (and enable some tricky React Native import
handling).

##### What's Changed

- Add an RN-specific bundle and consolidate imports by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2100](https://togithub.com/reduxjs/react-redux/pull/2100)

**Full Changelog**:
reduxjs/react-redux@v9.0.0...v9.0.1

###
[`v9.0.0`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.3...v9.0.0)

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](https://redux.js.org/usage/migrations/migrating-rtk-2)** 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!**](https://redux.js.org/usage/migrating-to-modern-redux))
> React-Redux is a separate, package, but we expect you'll be upgrading
them together.

```bash

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

##### RTK
npm install @&#8203;reduxjs/toolkit
yarn add @&#8203;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"](https://blog.isquaredsoftware.com/2023/08/esm-modernization-lessons/),
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](https://blog.isquaredsoftware.com/2023/08/esm-modernization-lessons/#problems-with-next-js-and-react-server-components).
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](https://togithub.com/reduxjs/react-redux/releases/tag/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:

```ts
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](https://legacy.reactjs.org/docs/higher-order-components.html#static-methods-must-be-copied-over),
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
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2038](https://togithub.com/reduxjs/react-redux/pull/2038)
- Add stack to dev mode checks by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2064](https://togithub.com/reduxjs/react-redux/pull/2064)
- add an extra entrypoint for React Server Components by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/2062](https://togithub.com/reduxjs/react-redux/pull/2062)
- Inline hoist-non-react-statics to eliminate a dep and help shaking by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2066](https://togithub.com/reduxjs/react-redux/pull/2066)
- Make context typing more accurate by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2041](https://togithub.com/reduxjs/react-redux/pull/2041)
- Fix `uSES` imports and run against RTK CI examples by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2070](https://togithub.com/reduxjs/react-redux/pull/2070)
- Copy CI setup for RTK examples by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2072](https://togithub.com/reduxjs/react-redux/pull/2072)
- Fix useSelector() in combination with lazy loaded components breaks
with react v18
([#&#8203;1977](https://togithub.com/reduxjs/react-redux/issues/1977))
by [@&#8203;jeroenpx](https://togithub.com/jeroenpx) in
[https://github.com/reduxjs/react-redux/pull/2068](https://togithub.com/reduxjs/react-redux/pull/2068)
- Actually add `sideEffects: "false"` to `package.json` in v9 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2079](https://togithub.com/reduxjs/react-redux/pull/2079)
- Inline `react-is` utils to fix tree-shaking in 9.0 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2085](https://togithub.com/reduxjs/react-redux/pull/2085)
- Rename `noopCheck` to `identityFunctionCheck` by
[@&#8203;aryaemami59](https://togithub.com/aryaemami59) in
[https://github.com/reduxjs/react-redux/pull/2091](https://togithub.com/reduxjs/react-redux/pull/2091)
- Use scoped JSX for React types by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2092](https://togithub.com/reduxjs/react-redux/pull/2092)

**Full Changelog**:
reduxjs/react-redux@v8.1.2...v9.0.0

###
[`v8.1.3`](https://togithub.com/reduxjs/react-redux/compare/v8.1.2...v8.1.3)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.2...v8.1.3)

###
[`v8.1.2`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.2)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.1...v8.1.2)

This version changes imports from the React package to namespace imports
so the package can safely be imported in React Server Components as long
as you don't actually use it - this is for example important if you want
to use the React-specifc `createApi` function from Redux Toolkit.

Some other changes:

- The behaviour of the "React Context Singletons" from 8.1.1 has been
adjusted to also work if you have multiple React instances of the same
version (those will now be separated) and if you are in an environment
without `globalThis` (in this case it will fall back to the previous
behaviour).
- We do no longer use Proxies, which should help with some very outdated
consumers, e.g. smart TVs, that cannot even polyfill Proxies.

**Full Changelog**:
reduxjs/react-redux@v8.1.1...v8.1.2

###
[`v8.1.1`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.1)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.0...v8.1.1)

This bugfix release tweaks the recent lazy context setup logic to ensure
a single React context instance per React version, and removes the
recently added RTK peerdep to fix an issue with Yarn workspaces.

#### Changelog

##### React Context Singletons

React Context has always relied on reference identity. If you have two
different copies of React or a library in a page, that can cause
multiple versions of a context instance to be created, leading to
problems like the infamous "Could not find react-redux context" error.

In
[v8.1.0](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.0),
we reworked the internals to lazily create our single
`ReactReduxContext` instance to avoid issues in a React Server
Components environment.

This release further tweaks that to stash a single context instance per
React version found in the page, thus hopefully avoiding the "multiple
copies of the same context" error in the future.

#### What's Changed

- fix: fix typescript error on non exported type by
[@&#8203;luzzif](https://togithub.com/luzzif) in
[https://github.com/reduxjs/react-redux/pull/2034](https://togithub.com/reduxjs/react-redux/pull/2034)
- create singleton context by React version by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/2039](https://togithub.com/reduxjs/react-redux/pull/2039)
- remove RTK peerDep by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[`44fc725`](https://togithub.com/reduxjs/react-redux/commit/44fc725)

**Full Changelog**:
reduxjs/react-redux@v8.1.0...v8.1.1

###
[`v8.1.0`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.7...v8.1.0)

This **feature release** adds new development-mode safety checks for
common errors (like poorly-written selectors), adds a workaround to fix
crash errors when React-Redux hooks are imported into React Server
Component files, and updates our hooks API docs page with improved
explanations and updated links.

#### Changelog

##### Development Mode Checks for `useSelector`

We've had a number of users tell us over time that it's common to
accidentally write selectors that have bad behavior and cause
performance issues. The most common causes of this are either selectors
that unconditionally return a new reference (such as `state =>
state.todos.map()` without any memoization ), or selectors that actually
return the *entire* root state ( `state => state` ).

We've updated `useSelector` to add safety checks in development mode
that warn if these incorrect behaviors are detected:

- Selectors will be called twice with the same inputs, and `useSelector`
will warn if the results are different references
- `useSelector` will warn if the selector result is actually the entire
root `state`

By default, **these checks only run *once* the first time `useSelector`
is called**. This should provide a good balance between detecting
possible issues, and keeping development mode execution performant
without adding many unnecessary extra selector calls.

If you want, you can configure this behavior globally by passing the
enum flags directly to `<Provider>`, or on a per-`useSelector` basis by
passing an options object as the second argument:

```ts
// Example: globally configure the root state "noop" check to run every time
<Provider store={store} noopCheck="always">
  {children}
</Provider>
```

```ts
// Example: configure `useSelector` to specifically run the reference checks differently:
function Component() {
  // Disable check entirely for this selector
  const count = useSelector(selectCount, { stabilityCheck: 'never' })
  // run once (default)
  const user = useSelector(selectUser, { stabilityCheck: 'once' })
  // ...
}
```

This goes along with the similar safety checks we've added to [Reselect
v5
alpha](https://togithub.com/reduxjs/reselect/releases/tag/v5.0.0-alpha.2)
as well.

##### Context Changes

We're still trying to work out how to properly use Redux and React
Server Components together. One possibility is using RTK Query's
`createApi` to define data fetching endpoints, and using the generated
thunks to fetch data in RSCs, but it's still an open question.

However, users have reported that merely importing *any* React-Redux API
in an RSC file causes a crash, because `React.createContext` is not
defined in RSC files. RTKQ's React-specific `createApi` entry point
imports React-Redux, so it's been unusable in RSCs.

This release adds a workaround to fix that issue, by using a proxy
wrapper around our singleton `ReactReduxContext` instance and lazily
creating that instance on demand. In testing, this appears to both
continue to work in all unit tests, *and* fixes the import error in an
RSC environment. We'd appreciate further feedback in case this change
does cause any issues for anyone!

We've also tweaked the internals of the hooks to do checks for correct
`<Provider>` usage when using a custom context, same as the default
context checks.

##### Docs Updates

We've cleaned up some of the Hooks API reference page, and updated links
to the React docs.

#### What's Changed

- check for Provider even when using custom context by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/1990](https://togithub.com/reduxjs/react-redux/pull/1990)
- Add a stability check, to see if selector returns stable result when
called with same parameters. by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2000](https://togithub.com/reduxjs/react-redux/pull/2000)
- Add an E2E-ish test that verifies behavior when imported into RSCs by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2030](https://togithub.com/reduxjs/react-redux/pull/2030)
- lazily create Context for RSC compat by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/2025](https://togithub.com/reduxjs/react-redux/pull/2025)
- Add warning for selectors that return the entire state by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2022](https://togithub.com/reduxjs/react-redux/pull/2022)

**Full Changelog**:
reduxjs/react-redux@v8.0.7...v8.1.0

###
[`v8.0.7`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.7)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.6...v8.0.7)

This release updates the peer dependencies to accept Redux Toolkit, and
accept the ongoing RTK and Redux core betas as valid peer deps.

> **Note**: These changes were initially in 8.0.6, but that had a typo
in the peer deps that broke installation. Sorry!

#### What's Changed

- Bump Redux peer deps to accept 5.0 betas, and bump RTK dev dep by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2017](https://togithub.com/reduxjs/react-redux/pull/2017)
- [`d45204f`](https://togithub.com/reduxjs/react-redux/commit/d45204f) :
Fix broken RTK peer dep

**Full Changelog**:
reduxjs/react-redux@v8.0.5...v8.0.7

###
[`v8.0.6`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.6)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.5...v8.0.6)

\~~This release updates the peer dependencies to accept Redux Toolkit,
and accept the ongoing RTK and Redux core betas as valid peer deps.~~

**This release has a peer deps typo that breaks installation - please
use 8.0.7 instead !**

#### What's Changed

- Bump Redux peer deps to accept 5.0 betas, and bump RTK dev dep by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2017](https://togithub.com/reduxjs/react-redux/pull/2017)

**Full Changelog**:
reduxjs/react-redux@v8.0.5...v8.0.6

###
[`v8.0.5`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.5)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.4...v8.0.5)

This release fixes a few minor TS issues.

#### What's Changed

- `Provider`: pass state (`S`) generic through to `ProviderProps` by
[@&#8203;OliverJAsh](https://togithub.com/OliverJAsh) in
[https://github.com/reduxjs/react-redux/pull/1960](https://togithub.com/reduxjs/react-redux/pull/1960)
- wrap `equalityFn` type in `NoInfer` by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/1965](https://togithub.com/reduxjs/react-redux/pull/1965)
- Fix wrapped component prop types when passing nullish
mapDispatchToProps by
[@&#8203;marconi1992](https://togithub.com/marconi1992) in
[https://github.com/reduxjs/react-redux/pull/1928](https://togithub.com/reduxjs/react-redux/pull/1928)

**Full Changelog**:
reduxjs/react-redux@v8.0.4...v8.0.5

###
[`v8.0.4`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.4)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.3...v8.0.4)

This patch release fixes some minor TS types issues, and updates the
rarely-used `areStatesEqual` option for `connect` to now pass through
`ownProps` for additional use in determining which pieces of state to
compare if desired.

> **Note**: 8.0.3 was accidentally published without one of these fixes.
Use 8.0.4 instead.

#### Changelog

##### TS Fixes

We've fixed an import of `React` that caused issues with the
`allowSyntheticDefaultImports` TS compiler flag in user projects.

`connect` already accepted a custom context instance as `props.context`,
and had runtime checks in case users were passing through a real value
with app data as `props.context` instead. However, the TS types did not
handle that case, and this would fail to compile. If your own component
expects `props.context` with actual data, `connect`'s types now use that
type instead.

The `ConnectedProps<T>` type had a mismatch with React's built-in
`React.ComponentProps<Component>` type, and that should now work
correctly.

##### Other Changes

The `areStatesEqual` option to `connect` now receives `ownProps` as
well, in case you need to make a more specific comparison with certain
sections of state.

The new signature is:

```ts
{
  areStatesEqual?: (
    nextState: State,
    prevState: State,
    nextOwnProps: TOwnProps,
    prevOwnProps: TOwnProps
  ) => boolean
}
```

#### What's Changed

- Don't require allowSyntheticDefaultImports: true by
[@&#8203;apepper](https://togithub.com/apepper) in
[https://github.com/reduxjs/react-redux/pull/1924](https://togithub.com/reduxjs/react-redux/pull/1924)
- Fixed type issue with `ComponentProps` from older `@types/react` by
[@&#8203;Andarist](https://togithub.com/Andarist) in
[https://github.com/reduxjs/react-redux/pull/1956](https://togithub.com/reduxjs/react-redux/pull/1956)
- connect: pass ownProps to areStatesEqual by
[@&#8203;jspurlin](https://togithub.com/jspurlin) in
[https://github.com/reduxjs/react-redux/pull/1951](https://togithub.com/reduxjs/react-redux/pull/1951)
- Omit built-in context prop if user component props include context by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1958](https://togithub.com/reduxjs/react-redux/pull/1958)

**Full Changelog**:
reduxjs/react-redux@v8.0.2...v8.0.4

###
[`v8.0.3`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.3)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.2...v8.0.3)

**This release was accidentally published without an intended fix -
please use
[v8.0.4](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.4)
instead**

###
[`v8.0.2`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.2)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.1...v8.0.2)

This patch release tweaks the behavior of `connect` to print a one-time
warning when the obsolete `pure` option is passed in, rather than
throwing an error. This fixes crashes caused by libraries such as
`react-beautiful-dnd` continuing to pass in that option (unnecessarily)
to React-Redux v8.

#### What's Changed

- Show warning instead of throwing error that pure option has been
removed by [@&#8203;ApacheEx](https://togithub.com/ApacheEx) in
[https://github.com/reduxjs/react-redux/pull/1922](https://togithub.com/reduxjs/react-redux/pull/1922)

**Full Changelog**:
reduxjs/react-redux@v8.0.1...v8.0.2

###
[`v8.0.1`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.1)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.0...v8.0.1)

This release fixes an incorrect internal import of our `Subscription`
type, which was causing TS compilation errors in some user projects.
We've also listed `@types/react-dom` as an optional peerDep. There are
no runtime changes in this release.

#### What's Changed

- Add optional peer dependency on
[@&#8203;types/react-dom](https://togithub.com/types/react-dom) by
[@&#8203;Methuselah96](https://togithub.com/Methuselah96) in
[https://github.com/reduxjs/react-redux/pull/1904](https://togithub.com/reduxjs/react-redux/pull/1904)
- fix(ts): incorrect import of `Subscription` causes `noImplicitAny`
error by [@&#8203;vicrep](https://togithub.com/vicrep) in
[https://github.com/reduxjs/react-redux/pull/1910](https://togithub.com/reduxjs/react-redux/pull/1910)

**Full Changelog**:
reduxjs/react-redux@v8.0.0...v8.0.1

###
[`v8.0.0`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v7.2.9...v8.0.0)

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 #&#8203;24304: React 18 types broken since
release**](https://togithub.com/facebook/react/issues/24304#issuecomment-1094565891)

Additionally, please see the React post on [**How to Ugprade to React
18**](https://reactjs.org/blog/2022/03/08/react-18-upgrade-guide.html)
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](https://togithub.com/reactwg/react-18/discussions/86). 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:

```ts
import { hydrateRoot } from 'react-dom/client'
import { configureStore } from '@&#8203;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](https://togithub.com/reduxjs/react-redux/issues/1737), 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](https://togithub.com/reduxjs/react-redux/issues/1879).
Instead, we direct users to [extract the `RootState` and `AppDispatch`
types from the store
setup](https://redux.js.org/tutorials/typescript-quick-start#define-root-state-and-dispatch-types),
and [create pre-typed versions of the React-Redux
hooks](https://redux.js.org/tutorials/typescript-quick-start#define-typed-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](https://togithub.com/reduxjs/react-redux/issues/1879#issuecomment-1073284804),
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](https://togithub.com/reduxjs/react-redux/issues/1236), 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
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1739](https://togithub.com/reduxjs/react-redux/pull/1739)
- Initial experimental React 18 compat prototyping by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1808](https://togithub.com/reduxjs/react-redux/pull/1808)
- Fix compatibility with React 18 strict effects by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1817](https://togithub.com/reduxjs/react-redux/pull/1817)
- Update to latest React 18 alpha dependencies by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1834](https://togithub.com/reduxjs/react-redux/pull/1834)
- Port remaining v7 typetests and improve v8 types by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1855](https://togithub.com/reduxjs/react-redux/pull/1855)
- Add initial SSR support for React 18 and React-Redux v8 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1835](https://togithub.com/reduxjs/react-redux/pull/1835)
- test: Adjust type tests to be compatible with React 18 typings by
[@&#8203;eps1lon](https://togithub.com/eps1lon) in
[https://github.com/reduxjs/react-redux/pull/1868](https://togithub.com/reduxjs/react-redux/pull/1868)
- Switch back to Subscription in useSelector to fix unsubscribe perf by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1870](https://togithub.com/reduxjs/react-redux/pull/1870)
- Cleanup more code after `pure` removal by
[@&#8203;Andarist](https://togithub.com/Andarist) in
[https://github.com/reduxjs/react-redux/pull/1859](https://togithub.com/reduxjs/react-redux/pull/1859)
- Swap `useSyncExternalStore` shim behavior and update React deps by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1884](https://togithub.com/reduxjs/react-redux/pull/1884)
- Remove `DefaultRootState` type by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1887](https://togithub.com/reduxjs/react-redux/pull/1887)
- Add SSR test for `serverState` behavior by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1888](https://togithub.com/reduxjs/react-redux/pull/1888)
- Cleanup internal types in selectorFactory.ts by
[@&#8203;Methuselah96](https://togithub.com/Methuselah96) in
[https://github.com/reduxjs/react-redux/pull/1889](https://togithub.com/reduxjs/react-redux/pull/1889)
- Remove ts-ignore for initMergeProps by
[@&#8203;Methuselah96](https://togithub.com/Methuselah96) in
[https://github.com/reduxjs/react-redux/pull/1891](https://togithub.com/reduxjs/react-redux/pull/1891)
- fix(deps): add optional peer deps into `peerDependencies` by
[@&#8203;kyletsang](https://togithub.com/kyletsang) in
[https://github.com/reduxjs/react-redux/pull/1893](https://togithub.com/reduxjs/react-redux/pull/1893)
- Update peer deps for v8 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1895](https://togithub.com/reduxjs/react-redux/pull/1895)
- Port DT fix for `dispatchProp` arg in `mergeProps` by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1897](https://togithub.com/reduxjs/react-redux/pull/1897)
- Update docs for v8 final by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1902](https://togithub.com/reduxjs/react-redux/pull/1902)

</details>

---

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America/Los_Angeles, Automerge - "after 5pm,every weekend" in timezone
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♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
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🔕 **Ignore**: Close this PR and you won't be reminded about this update
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---

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Co-authored-by: Jean Regisser <jean.regisser@gmail.com>
shottah referenced this pull request in zed-io/kolektivo May 15, 2024
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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [react-redux](https://togithub.com/reduxjs/react-redux) | [`^7.2.9` ->
`^9.1.0`](https://renovatebot.com/diffs/npm/react-redux/7.2.9/9.1.0) |
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|
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|
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|
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|

---

### Release Notes

<details>
<summary>reduxjs/react-redux (react-redux)</summary>

###
[`v9.1.0`](https://togithub.com/reduxjs/react-redux/compare/v9.0.4...v9.1.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.4...v9.1.0)

###
[`v9.0.4`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.4)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.3...v9.0.4)

This **bugfix release** updates the React Native peer dependency to be
`>= 0.69`, to better reflect the need for React 18 compat and
(hopefully) resolve issues with the `npm` package manager throwing peer
dep errors on install.

#### What's Changed

- Allow react-native newer than 0.69 as peer dependency by
[@&#8203;R3DST0RM](https://togithub.com/R3DST0RM) in
[https://github.com/reduxjs/react-redux/pull/2107](https://togithub.com/reduxjs/react-redux/pull/2107)

**Full Changelog**:
reduxjs/react-redux@v9.0.3...v9.0.4

###
[`v9.0.3`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.3)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.2...v9.0.3)

This **bugfix release** drops the ReactDOM / React Native specific use
of render batching, as React 18 now automatically batches, and updates
the React types dependencies

#### Changelog

##### Batching Dependency Updates

React-Redux has long depended on React's `unstable_batchedUpdates` API
to help batch renders queued by Redux updates. It also re-exported that
method as a util named `batch`.

However, React 18 now auto-batches all queued renders in the same event
loop tick, so `unstable_batchedUpdates` is effectively a no-op.

Using `unstable_batchedUpdates` has always been a pain point, because
it's exported by the renderer package (ReactDOM or React Native), rather
than the core `react` package. Our prior implementation relied on having
separate `batch.ts` and `batch.native.ts` files in the codebase, and
expecting React Native's bundler to find the right transpiled file at
app build time. Now that we're pre-bundling artifacts in React-Redux v9,
that approach has become a problem.

Given that React 18 already batches by default, there's no further need
to continue using `unstable_batchedUpdates` internally, so we've removed
our use of that and simplified the internals.

We still export a `batch` method, but it's effectively a no-op that just
immediately runs the given callback, and we've marked it as
`@deprecated`.

We've also updated the build artifacts and packaging, as there's no
longer a need for an `alternate-renderers` entry point that omits
batching, or a separate artifact that imports from `"react-native"`.

#### What's Changed

- Drop renderer-specific batching behavior and deprecate `batch` by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2104](https://togithub.com/reduxjs/react-redux/pull/2104)
- Drop `@types/react-dom` and lower `@types/react` to min needed by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2105](https://togithub.com/reduxjs/react-redux/pull/2105)

**Full Changelog**:
reduxjs/react-redux@v9.0.2...v9.0.3

###
[`v9.0.2`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.2)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.1...v9.0.2)

This **bugfix release** makes additional tweaks to the React Native
artifact filename to help resolve import and bundling issues with RN
projects.

#### What's Changed

- Change react-native output extension from `.mjs` to `.js` by
[@&#8203;aryaemami59](https://togithub.com/aryaemami59) in
[https://github.com/reduxjs/react-redux/pull/2102](https://togithub.com/reduxjs/react-redux/pull/2102)

**Full Changelog**:
reduxjs/react-redux@v9.0.1...v9.0.2

###
[`v9.0.1`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.1)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v9.0.0...v9.0.1)

This **bugfix release** updates the package to include a new
`react-redux.react-native.js` bundle that specifically imports React
Native, and consolidates all of the `'react'` imports into one file to
save on bundle size (and enable some tricky React Native import
handling).

##### What's Changed

- Add an RN-specific bundle and consolidate imports by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2100](https://togithub.com/reduxjs/react-redux/pull/2100)

**Full Changelog**:
reduxjs/react-redux@v9.0.0...v9.0.1

###
[`v9.0.0`](https://togithub.com/reduxjs/react-redux/releases/tag/v9.0.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.3...v9.0.0)

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](https://redux.js.org/usage/migrations/migrating-rtk-2)** 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!**](https://redux.js.org/usage/migrating-to-modern-redux))
> React-Redux is a separate, package, but we expect you'll be upgrading
them together.

```bash

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

##### RTK
npm install @&#8203;reduxjs/toolkit
yarn add @&#8203;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"](https://blog.isquaredsoftware.com/2023/08/esm-modernization-lessons/),
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](https://blog.isquaredsoftware.com/2023/08/esm-modernization-lessons/#problems-with-next-js-and-react-server-components).
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](https://togithub.com/reduxjs/react-redux/releases/tag/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:

```ts
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](https://legacy.reactjs.org/docs/higher-order-components.html#static-methods-must-be-copied-over),
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
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2038](https://togithub.com/reduxjs/react-redux/pull/2038)
- Add stack to dev mode checks by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2064](https://togithub.com/reduxjs/react-redux/pull/2064)
- add an extra entrypoint for React Server Components by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/2062](https://togithub.com/reduxjs/react-redux/pull/2062)
- Inline hoist-non-react-statics to eliminate a dep and help shaking by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2066](https://togithub.com/reduxjs/react-redux/pull/2066)
- Make context typing more accurate by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2041](https://togithub.com/reduxjs/react-redux/pull/2041)
- Fix `uSES` imports and run against RTK CI examples by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2070](https://togithub.com/reduxjs/react-redux/pull/2070)
- Copy CI setup for RTK examples by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2072](https://togithub.com/reduxjs/react-redux/pull/2072)
- Fix useSelector() in combination with lazy loaded components breaks
with react v18
([#&#8203;1977](https://togithub.com/reduxjs/react-redux/issues/1977))
by [@&#8203;jeroenpx](https://togithub.com/jeroenpx) in
[https://github.com/reduxjs/react-redux/pull/2068](https://togithub.com/reduxjs/react-redux/pull/2068)
- Actually add `sideEffects: "false"` to `package.json` in v9 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2079](https://togithub.com/reduxjs/react-redux/pull/2079)
- Inline `react-is` utils to fix tree-shaking in 9.0 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2085](https://togithub.com/reduxjs/react-redux/pull/2085)
- Rename `noopCheck` to `identityFunctionCheck` by
[@&#8203;aryaemami59](https://togithub.com/aryaemami59) in
[https://github.com/reduxjs/react-redux/pull/2091](https://togithub.com/reduxjs/react-redux/pull/2091)
- Use scoped JSX for React types by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2092](https://togithub.com/reduxjs/react-redux/pull/2092)

**Full Changelog**:
reduxjs/react-redux@v8.1.2...v9.0.0

###
[`v8.1.3`](https://togithub.com/reduxjs/react-redux/compare/v8.1.2...v8.1.3)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.2...v8.1.3)

###
[`v8.1.2`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.2)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.1...v8.1.2)

This version changes imports from the React package to namespace imports
so the package can safely be imported in React Server Components as long
as you don't actually use it - this is for example important if you want
to use the React-specifc `createApi` function from Redux Toolkit.

Some other changes:

- The behaviour of the "React Context Singletons" from 8.1.1 has been
adjusted to also work if you have multiple React instances of the same
version (those will now be separated) and if you are in an environment
without `globalThis` (in this case it will fall back to the previous
behaviour).
- We do no longer use Proxies, which should help with some very outdated
consumers, e.g. smart TVs, that cannot even polyfill Proxies.

**Full Changelog**:
reduxjs/react-redux@v8.1.1...v8.1.2

###
[`v8.1.1`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.1)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.1.0...v8.1.1)

This bugfix release tweaks the recent lazy context setup logic to ensure
a single React context instance per React version, and removes the
recently added RTK peerdep to fix an issue with Yarn workspaces.

#### Changelog

##### React Context Singletons

React Context has always relied on reference identity. If you have two
different copies of React or a library in a page, that can cause
multiple versions of a context instance to be created, leading to
problems like the infamous "Could not find react-redux context" error.

In
[v8.1.0](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.0),
we reworked the internals to lazily create our single
`ReactReduxContext` instance to avoid issues in a React Server
Components environment.

This release further tweaks that to stash a single context instance per
React version found in the page, thus hopefully avoiding the "multiple
copies of the same context" error in the future.

#### What's Changed

- fix: fix typescript error on non exported type by
[@&#8203;luzzif](https://togithub.com/luzzif) in
[https://github.com/reduxjs/react-redux/pull/2034](https://togithub.com/reduxjs/react-redux/pull/2034)
- create singleton context by React version by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/2039](https://togithub.com/reduxjs/react-redux/pull/2039)
- remove RTK peerDep by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[`44fc725`](https://togithub.com/reduxjs/react-redux/commit/44fc725)

**Full Changelog**:
reduxjs/react-redux@v8.1.0...v8.1.1

###
[`v8.1.0`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.1.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.7...v8.1.0)

This **feature release** adds new development-mode safety checks for
common errors (like poorly-written selectors), adds a workaround to fix
crash errors when React-Redux hooks are imported into React Server
Component files, and updates our hooks API docs page with improved
explanations and updated links.

#### Changelog

##### Development Mode Checks for `useSelector`

We've had a number of users tell us over time that it's common to
accidentally write selectors that have bad behavior and cause
performance issues. The most common causes of this are either selectors
that unconditionally return a new reference (such as `state =>
state.todos.map()` without any memoization ), or selectors that actually
return the *entire* root state ( `state => state` ).

We've updated `useSelector` to add safety checks in development mode
that warn if these incorrect behaviors are detected:

- Selectors will be called twice with the same inputs, and `useSelector`
will warn if the results are different references
- `useSelector` will warn if the selector result is actually the entire
root `state`

By default, **these checks only run *once* the first time `useSelector`
is called**. This should provide a good balance between detecting
possible issues, and keeping development mode execution performant
without adding many unnecessary extra selector calls.

If you want, you can configure this behavior globally by passing the
enum flags directly to `<Provider>`, or on a per-`useSelector` basis by
passing an options object as the second argument:

```ts
// Example: globally configure the root state "noop" check to run every time
<Provider store={store} noopCheck="always">
  {children}
</Provider>
```

```ts
// Example: configure `useSelector` to specifically run the reference checks differently:
function Component() {
  // Disable check entirely for this selector
  const count = useSelector(selectCount, { stabilityCheck: 'never' })
  // run once (default)
  const user = useSelector(selectUser, { stabilityCheck: 'once' })
  // ...
}
```

This goes along with the similar safety checks we've added to [Reselect
v5
alpha](https://togithub.com/reduxjs/reselect/releases/tag/v5.0.0-alpha.2)
as well.

##### Context Changes

We're still trying to work out how to properly use Redux and React
Server Components together. One possibility is using RTK Query's
`createApi` to define data fetching endpoints, and using the generated
thunks to fetch data in RSCs, but it's still an open question.

However, users have reported that merely importing *any* React-Redux API
in an RSC file causes a crash, because `React.createContext` is not
defined in RSC files. RTKQ's React-specific `createApi` entry point
imports React-Redux, so it's been unusable in RSCs.

This release adds a workaround to fix that issue, by using a proxy
wrapper around our singleton `ReactReduxContext` instance and lazily
creating that instance on demand. In testing, this appears to both
continue to work in all unit tests, *and* fixes the import error in an
RSC environment. We'd appreciate further feedback in case this change
does cause any issues for anyone!

We've also tweaked the internals of the hooks to do checks for correct
`<Provider>` usage when using a custom context, same as the default
context checks.

##### Docs Updates

We've cleaned up some of the Hooks API reference page, and updated links
to the React docs.

#### What's Changed

- check for Provider even when using custom context by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/1990](https://togithub.com/reduxjs/react-redux/pull/1990)
- Add a stability check, to see if selector returns stable result when
called with same parameters. by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2000](https://togithub.com/reduxjs/react-redux/pull/2000)
- Add an E2E-ish test that verifies behavior when imported into RSCs by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2030](https://togithub.com/reduxjs/react-redux/pull/2030)
- lazily create Context for RSC compat by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/2025](https://togithub.com/reduxjs/react-redux/pull/2025)
- Add warning for selectors that return the entire state by
[@&#8203;EskiMojo14](https://togithub.com/EskiMojo14) in
[https://github.com/reduxjs/react-redux/pull/2022](https://togithub.com/reduxjs/react-redux/pull/2022)

**Full Changelog**:
reduxjs/react-redux@v8.0.7...v8.1.0

###
[`v8.0.7`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.7)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.6...v8.0.7)

This release updates the peer dependencies to accept Redux Toolkit, and
accept the ongoing RTK and Redux core betas as valid peer deps.

> **Note**: These changes were initially in 8.0.6, but that had a typo
in the peer deps that broke installation. Sorry!

#### What's Changed

- Bump Redux peer deps to accept 5.0 betas, and bump RTK dev dep by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2017](https://togithub.com/reduxjs/react-redux/pull/2017)
- [`d45204f`](https://togithub.com/reduxjs/react-redux/commit/d45204f) :
Fix broken RTK peer dep

**Full Changelog**:
reduxjs/react-redux@v8.0.5...v8.0.7

###
[`v8.0.6`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.6)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.5...v8.0.6)

\~~This release updates the peer dependencies to accept Redux Toolkit,
and accept the ongoing RTK and Redux core betas as valid peer deps.~~

**This release has a peer deps typo that breaks installation - please
use 8.0.7 instead !**

#### What's Changed

- Bump Redux peer deps to accept 5.0 betas, and bump RTK dev dep by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/2017](https://togithub.com/reduxjs/react-redux/pull/2017)

**Full Changelog**:
reduxjs/react-redux@v8.0.5...v8.0.6

###
[`v8.0.5`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.5)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.4...v8.0.5)

This release fixes a few minor TS issues.

#### What's Changed

- `Provider`: pass state (`S`) generic through to `ProviderProps` by
[@&#8203;OliverJAsh](https://togithub.com/OliverJAsh) in
[https://github.com/reduxjs/react-redux/pull/1960](https://togithub.com/reduxjs/react-redux/pull/1960)
- wrap `equalityFn` type in `NoInfer` by
[@&#8203;phryneas](https://togithub.com/phryneas) in
[https://github.com/reduxjs/react-redux/pull/1965](https://togithub.com/reduxjs/react-redux/pull/1965)
- Fix wrapped component prop types when passing nullish
mapDispatchToProps by
[@&#8203;marconi1992](https://togithub.com/marconi1992) in
[https://github.com/reduxjs/react-redux/pull/1928](https://togithub.com/reduxjs/react-redux/pull/1928)

**Full Changelog**:
reduxjs/react-redux@v8.0.4...v8.0.5

###
[`v8.0.4`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.4)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.3...v8.0.4)

This patch release fixes some minor TS types issues, and updates the
rarely-used `areStatesEqual` option for `connect` to now pass through
`ownProps` for additional use in determining which pieces of state to
compare if desired.

> **Note**: 8.0.3 was accidentally published without one of these fixes.
Use 8.0.4 instead.

#### Changelog

##### TS Fixes

We've fixed an import of `React` that caused issues with the
`allowSyntheticDefaultImports` TS compiler flag in user projects.

`connect` already accepted a custom context instance as `props.context`,
and had runtime checks in case users were passing through a real value
with app data as `props.context` instead. However, the TS types did not
handle that case, and this would fail to compile. If your own component
expects `props.context` with actual data, `connect`'s types now use that
type instead.

The `ConnectedProps<T>` type had a mismatch with React's built-in
`React.ComponentProps<Component>` type, and that should now work
correctly.

##### Other Changes

The `areStatesEqual` option to `connect` now receives `ownProps` as
well, in case you need to make a more specific comparison with certain
sections of state.

The new signature is:

```ts
{
  areStatesEqual?: (
    nextState: State,
    prevState: State,
    nextOwnProps: TOwnProps,
    prevOwnProps: TOwnProps
  ) => boolean
}
```

#### What's Changed

- Don't require allowSyntheticDefaultImports: true by
[@&#8203;apepper](https://togithub.com/apepper) in
[https://github.com/reduxjs/react-redux/pull/1924](https://togithub.com/reduxjs/react-redux/pull/1924)
- Fixed type issue with `ComponentProps` from older `@types/react` by
[@&#8203;Andarist](https://togithub.com/Andarist) in
[https://github.com/reduxjs/react-redux/pull/1956](https://togithub.com/reduxjs/react-redux/pull/1956)
- connect: pass ownProps to areStatesEqual by
[@&#8203;jspurlin](https://togithub.com/jspurlin) in
[https://github.com/reduxjs/react-redux/pull/1951](https://togithub.com/reduxjs/react-redux/pull/1951)
- Omit built-in context prop if user component props include context by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1958](https://togithub.com/reduxjs/react-redux/pull/1958)

**Full Changelog**:
reduxjs/react-redux@v8.0.2...v8.0.4

###
[`v8.0.3`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.3)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.2...v8.0.3)

**This release was accidentally published without an intended fix -
please use
[v8.0.4](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.4)
instead**

###
[`v8.0.2`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.2)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.1...v8.0.2)

This patch release tweaks the behavior of `connect` to print a one-time
warning when the obsolete `pure` option is passed in, rather than
throwing an error. This fixes crashes caused by libraries such as
`react-beautiful-dnd` continuing to pass in that option (unnecessarily)
to React-Redux v8.

#### What's Changed

- Show warning instead of throwing error that pure option has been
removed by [@&#8203;ApacheEx](https://togithub.com/ApacheEx) in
[https://github.com/reduxjs/react-redux/pull/1922](https://togithub.com/reduxjs/react-redux/pull/1922)

**Full Changelog**:
reduxjs/react-redux@v8.0.1...v8.0.2

###
[`v8.0.1`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.1)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v8.0.0...v8.0.1)

This release fixes an incorrect internal import of our `Subscription`
type, which was causing TS compilation errors in some user projects.
We've also listed `@types/react-dom` as an optional peerDep. There are
no runtime changes in this release.

#### What's Changed

- Add optional peer dependency on
[@&#8203;types/react-dom](https://togithub.com/types/react-dom) by
[@&#8203;Methuselah96](https://togithub.com/Methuselah96) in
[https://github.com/reduxjs/react-redux/pull/1904](https://togithub.com/reduxjs/react-redux/pull/1904)
- fix(ts): incorrect import of `Subscription` causes `noImplicitAny`
error by [@&#8203;vicrep](https://togithub.com/vicrep) in
[https://github.com/reduxjs/react-redux/pull/1910](https://togithub.com/reduxjs/react-redux/pull/1910)

**Full Changelog**:
reduxjs/react-redux@v8.0.0...v8.0.1

###
[`v8.0.0`](https://togithub.com/reduxjs/react-redux/releases/tag/v8.0.0)

[Compare
Source](https://togithub.com/reduxjs/react-redux/compare/v7.2.9...v8.0.0)

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 #&#8203;24304: React 18 types broken since
release**](https://togithub.com/facebook/react/issues/24304#issuecomment-1094565891)

Additionally, please see the React post on [**How to Ugprade to React
18**](https://reactjs.org/blog/2022/03/08/react-18-upgrade-guide.html)
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](https://togithub.com/reactwg/react-18/discussions/86). 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:

```ts
import { hydrateRoot } from 'react-dom/client'
import { configureStore } from '@&#8203;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](https://togithub.com/reduxjs/react-redux/issues/1737), 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](https://togithub.com/reduxjs/react-redux/issues/1879).
Instead, we direct users to [extract the `RootState` and `AppDispatch`
types from the store
setup](https://redux.js.org/tutorials/typescript-quick-start#define-root-state-and-dispatch-types),
and [create pre-typed versions of the React-Redux
hooks](https://redux.js.org/tutorials/typescript-quick-start#define-typed-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](https://togithub.com/reduxjs/react-redux/issues/1879#issuecomment-1073284804),
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](https://togithub.com/reduxjs/react-redux/issues/1236), 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
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1739](https://togithub.com/reduxjs/react-redux/pull/1739)
- Initial experimental React 18 compat prototyping by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1808](https://togithub.com/reduxjs/react-redux/pull/1808)
- Fix compatibility with React 18 strict effects by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1817](https://togithub.com/reduxjs/react-redux/pull/1817)
- Update to latest React 18 alpha dependencies by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1834](https://togithub.com/reduxjs/react-redux/pull/1834)
- Port remaining v7 typetests and improve v8 types by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1855](https://togithub.com/reduxjs/react-redux/pull/1855)
- Add initial SSR support for React 18 and React-Redux v8 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1835](https://togithub.com/reduxjs/react-redux/pull/1835)
- test: Adjust type tests to be compatible with React 18 typings by
[@&#8203;eps1lon](https://togithub.com/eps1lon) in
[https://github.com/reduxjs/react-redux/pull/1868](https://togithub.com/reduxjs/react-redux/pull/1868)
- Switch back to Subscription in useSelector to fix unsubscribe perf by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1870](https://togithub.com/reduxjs/react-redux/pull/1870)
- Cleanup more code after `pure` removal by
[@&#8203;Andarist](https://togithub.com/Andarist) in
[https://github.com/reduxjs/react-redux/pull/1859](https://togithub.com/reduxjs/react-redux/pull/1859)
- Swap `useSyncExternalStore` shim behavior and update React deps by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1884](https://togithub.com/reduxjs/react-redux/pull/1884)
- Remove `DefaultRootState` type by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1887](https://togithub.com/reduxjs/react-redux/pull/1887)
- Add SSR test for `serverState` behavior by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1888](https://togithub.com/reduxjs/react-redux/pull/1888)
- Cleanup internal types in selectorFactory.ts by
[@&#8203;Methuselah96](https://togithub.com/Methuselah96) in
[https://github.com/reduxjs/react-redux/pull/1889](https://togithub.com/reduxjs/react-redux/pull/1889)
- Remove ts-ignore for initMergeProps by
[@&#8203;Methuselah96](https://togithub.com/Methuselah96) in
[https://github.com/reduxjs/react-redux/pull/1891](https://togithub.com/reduxjs/react-redux/pull/1891)
- fix(deps): add optional peer deps into `peerDependencies` by
[@&#8203;kyletsang](https://togithub.com/kyletsang) in
[https://github.com/reduxjs/react-redux/pull/1893](https://togithub.com/reduxjs/react-redux/pull/1893)
- Update peer deps for v8 by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1895](https://togithub.com/reduxjs/react-redux/pull/1895)
- Port DT fix for `dispatchProp` arg in `mergeProps` by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1897](https://togithub.com/reduxjs/react-redux/pull/1897)
- Update docs for v8 final by
[@&#8203;markerikson](https://togithub.com/markerikson) in
[https://github.com/reduxjs/react-redux/pull/1902](https://togithub.com/reduxjs/react-redux/pull/1902)

</details>

---

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♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
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🔕 **Ignore**: Close this PR and you won't be reminded about this update
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---

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