Mark Redux as an optional peer dependency

[xty]

TL;DR: With the introduction of @reduxjs/toolkit, we can now use it in place of redux, thus making both peer dependencies optional.

As suggested by @markerikson in reduxjs/redux-toolkit#238 (comment),

One other small downside is that React-Redux says it wants Redux as a peer, and logs a warning if only RSK is installed.

Currently, this warning may very well give the false impression that @reduxjs/toolkit must be installed alongside redux for it to work properly.

Ideally, an UNMET PEER DEPENDENCY warning should by displayed iff neither redux nor @reduxjs/toolkit is installed, but neither npm nor yarn has a way to specify such a requirement AFAIK. That leaves us no choice but to mark both as optional (similar to the react-dom-vs-react-native situation), if we are to avoid being misleading.

In the future, leaving redux as is might pose a bigger problem still with npm v7, which will install peer dependencies automatically, as outlined in the npm CLI Roadmap among other places:

Proper peerDependencies Support

Part of the installer rewrite involves taking a fresh look at how peerDependencies are handled (and, quite often, not handled) to maximize the cases where the CLI does the right thing. Since npm v3, peerDependencies were not installed by default, putting the onus on users to resolve them. We'll be bringing back this functionality in version 7.

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[timdorr]

What about the fact that RTK requests redux@^4, whereas React Redux is compatible with redux@^2-4? I suppose we should bump up to the same ^4 dependency.

Another option: What if RTK re-exported React Redux? Sort of akin to react-router-dom re-exporting all of react-router.

[markerikson]

RTK is supposed to be independent of React-Redux and usable with any UI layer, in the same way that the Redux core is. So no, RTK can't depend on React-Redux at all.

Right now, using RTK + React-Redux shows a warning at install time, but we get away with it at runtime because of how package managers and bundlers end up handling things (nested dependencies get flattened to the root of node_modules, and you can have import statements for transitive packages without explicitly listing them in package.json because of that flattened hierarchy).

In terms of the actual source code, the only true dependency React-Redux has on Redux is the two places where we import bindActionCreators (

react-redux/src/connect/mapDispatchToProps.js

Line 1 in 0c048f0

import { bindActionCreators } from 'redux'

and

react-redux/src/utils/wrapActionCreators.js

Line 1 in 3e53ff9

import { bindActionCreators } from 'redux'

).

The store shape aspect (ie, expecting store to be an object like {dispatch, subscribe, getState}) is more of an implicit / duck-typing kind of thing.

So, strictly speaking, React-Redux itself is indeed compatible with redux@^2, because all it needs is bindActionCreators + something store-like.

If we were to copy-paste bindActionCreators over, we could remove the dependency on Redux entirely, and mark both Redux and RTK as purely optional. That said, not sure if it's the right approach or not.

[markerikson]

FWIW, bindActionCreators is all of 25-ish lines long. I vote we just copy-paste it over. We could even make the shape checks be dev-only to shave a few bytes.

For that matter, in theory you should only get that if you're using connect anyway. If you're only using the hooks API, that should never get imported.

From there we add RTK and Redux as optional peerDeps, but all you really need is a Redux-store-shaped store passed to Provider.

[timdorr]

Just did that over in #1705

[xty]

Well done, guys