Nested `connect` updates are not batched

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Bug

What is the current behavior?

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Your bug will get fixed much faster if we can run your code and it doesn’t have dependencies other than React. Paste the link to a CodeSandbox (https://codesandbox.io/s/new) or RN Snack (https://snack.expo.io/) example below:

https://stackblitz.com/edit/react-redux-batching-xkhtq8?file=index.tsx

What is the expected behavior?

1. Open https://react-redux-batching-xkhtq8.stackblitz.io/
2. Open dev tools -> React profiler
3. Click “reload and start profiling”
4. After reload, end profiling

Expected: 2 commits:

1. First render
2. Counter and ReduxCounter update, triggered via dispatch inside Counter#componentDidMount

Actual: 3 commits:

1. First render
2. Counter update, triggered via dispatch inside Counter#componentDidMount
3. ReduxCounter update, triggered via dispatch inside Counter#componentDidMount

IIUC, there is no reason why 2 and 3 can not be batched into a single React re-render?

Which versions of React, ReactDOM/React Native, Redux, and React Redux are you using? Which browser and OS are affected by this issue? Did this work in previous versions of React Redux?

Update: note this issue does not occur when using useSelector. https://stackblitz.com/edit/react-redux-batching-zb1wxv?file=index.tsx

[markerikson]

And I’m saying there’s two different aspects here:

• Whether nested updates at the same level are batched
• Whether nested updates at different levels are batched

We currently do the first, but not the second.

[markerikson]

I’m going to close this as a WONTFIX for now, largely because we’re encouraging folks to stop using connect (even though it’ll be fully supported in v8). This is a real bit of behavior that I can understand is annoying, but I don’t think there’s a meaningful change we can make at this point, and I don’t intend to spend time fixing it myself.

If someone still feels strongly about this please comment, or even better file a PR to improve behavior here.