Bug: `Cannot update a component (xxx) while rendering a different component (yyy)` on user click

[alicerocheman]

I'm encountering the Cannot update a component (xxx) while rendering a different component (yyy) on user click. The state setter is called inside a useCallback, which is called several components "below", inside a useCallback. As the user decides when they click, I don't understand how I could prevent this error, and am not sure whether the error should fire in this case.

React version: 17.0.2

Steps To Reproduce

1. create a Parent component that contains this:

  const [showError, setShowError] = useState(false);
  const [scrollToError, setScrollToError] = useState(false);
  const handleShowError = useCallback(() => {
    setShowError(true);
    setScrollToError(true);
  }, []);
  const handleStopShowingError = useCallback(() => {
    setShowError(false); // this produces the error when called in step 3
    setScrollToError(false);
  }, []);
  const handleStopScrollToError = useCallback(() => {
    setScrollToError(false);
  }, []);

2. pass those through a child, and its child and its child FinalChild, that all do other things, including listening to contexts and updating stuff.
3. in FinalChild, use the callbacks this way:

  const onClick = useCallback(() => {
    setIsOpen((isOpen) => {
      if (isOpen) {
        if (isValid) {
          handlers.handleComplete();
          return false;
        } else {
          handleShowError(); 
          return true;
        }
      } else {
        if (isDisabled) {
          handleShowError();
          return false;
        } else {
          handleStopShowingError(); // this produces the error (that goes up to parent in step 1)
          if (!isPreviousTabCompleted) handleCompletePreviousTabs(_index);
          return true;
        }
      }
    });
  }, [
    handleShowError,
    handleStopShowingError,
    handleCompletePreviousTabs,
    handlers,
    _index,
    isValid,
    isDisabled,
    isPreviousTabCompleted,
  ]);
  return <button onClick={onClick}>Click me</button>

Link to code example: I couldn't reproduce outside of my working repo, as the error does not appear when render is fast on typical simple components.

The current behavior

When user clicks, I get the Cannot update a component (xxx) while rendering a different component (yyy) error

The expected behavior

Honnestly I don't know what should happen, it seems weird that the error pops up, even though I'm never calling the setter outside of a hook (always inside a useCallback) and user should be able to click when they want... I understand the error is there to inform me that there is an issue with my code, but I don't know how I could improve this code. Shouldn't the useCallback deal with this?

[lubieowoce]

I couldn't find a reference for this, but it's possible that you're not allowed to do side-effects in the updater-function you pass to a setState. (i'm assuming setIsOpen comes from a const [isOpen, setIsOpen] = useState(...)).

I.e. I don't think something like this is allowed:

const [first, setFirst] = useState(0);
const [second, setSecond] = useState(0);
const probablyIllegal = () => {
  setSecond((prevSecond) => {
    setFirst(0); // ❌❌❌
    return prevSecond + 1;
  }):
}

(This code by itself seems to work, but I imagine it'd break when you split it across multiple components, like yours is)

EDIT: Seems similar to https://github.com/facebook/react/issues/15240#issuecomment-478247348:

You cannot perform side effects in that callback, it must be a pure function that returns new state.

[gaearon]

This sounds likely because updater functions run during rendering.

[hubertlepicki]

To the good people that find this thread and are wondering what @gaearon tip means: you likely to have the following code in your child component:

if (someVariableChanged) {
  setSomeState(...)
}

In my case, I had to change it to useEffect like this:

useEffect(() => {
  setSomeState(...)
}, [someVariableChanged]

[jatinbansal1305]

The error you are encountering, "Cannot update a component while rendering a different component," typically occurs when you attempt to update the state of a component while it is still rendering. This can happen when you call a state setter function (like setShowError) inside a useCallback hook that is triggered during rendering.

To prevent this error, you can use the useEffect hook to perform state updates after the rendering is complete.

[github-actions[bot]]

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[github-actions[bot]]

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