React warning with JSX eventContent "flushSync was called from inside a lifecycle method"

[AmruthPillai]

Reduced Test Case

Do you understand that if a reduced test case is not provided, we will intentionally delay triaging of your ticket?

• I understand

Which connector are you using (React/Angular/etc)?

React

Bug Description

When I updated to the latest version v6.1.7, started facing this issue.

There's no visual bug, but I keep getting this warning fired many times when the calendar view updates.

Warning: flushSync was called from inside a lifecycle method. React cannot flush when React is already rendering. Consider moving this call to a scheduler task or micro task.

[walerun]

the same for me 🤔

[cbaconnier]

Happening to me as well on React.
For me it seems to come from eventContent.

  const renderEventContent = (eventInfo: EventContentArg) => {
    return (
      <div>{/* ... */}</div>
    )
  }

// ...

<FullCalendar
    eventContent={renderEventContent}
/>

Edit: Seems that "fix unnecessary calls to eventContent" in the latest release was necessary after all 😅
https://github.com/fullcalendar/fullcalendar/releases/tag/v6.1.7

[Arithmetics]

same for me

[acerix]

Would you be able to post a runnable, stripped-down demonstration of the bug? Would really appreciate it because the time saved reproducing will be time spent fixing.

The React example project uses eventContent like that but I don't see any warning:

https://stackblitz.com/github/fullcalendar/fullcalendar-examples/tree/main/react

[cbaconnier]

Would you be able to post a runnable, stripped-down demonstration of the bug? Would really appreciate it because the time saved reproducing will be time spent fixing.

The React example project uses eventContent like that but I don't see any warning:

https://stackblitz.com/github/fullcalendar/fullcalendar-examples/tree/main/react

@acerix
This is what I see in the console when I run your example and click on toggle weekends.

Also, as I said earlier, as soon as we remove eventContent={renderEventContent} the error is gone.

[acerix]

Thanks for the info, I also see the warning after toggle weekends.

[RomOleg]

Same with "resourceAreaColumns" when you specify cellContent: () => { return ( MyComponent ) }

[gursidak]

one more clue this warning is logged the same number of time as the lenght of events array, sometimes in its multiple, like if 101 events are supplied, it will log 101 times this warning, in my case when i drag to select range of dates, it logs this warning "length of events array" times .

[arshaw]

This is now fixed in v6.1.8

Updated repro:
https://stackblitz.com/edit/github-bv3xxu?file=package.json