Custom EventWrapper with DnD extension not rendering correctly

[palagonKevo]

Check that this is really a bug

• I confirm

Reproduction link

https://codesandbox.io/p/sandbox/4rsg7w

Bug description

Custom EventWrapper with DnD add-on is bugged, it's not rendering correctly. Whenever you add a custom component in the components prop, it crashes and doesn't render the component at all.

Expected Behavior

Seems to be an issue while executing mergeComponents function, which is taking keys as undefined and the forEach function is stating that can't use forEach for undefined. In previous versions, this was working as expected.

Actual Behavior

The whole component is crashing

react-big-calendar version

^1.17.1

React version

^19.0.0

Platform/Target and Browser Versions

Any

Validations

• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.
• Make sure this is a react-big-calendar issue and not an implementation issue

Would you like to open a PR for this bug?

• I'm willing to open a PR

[7assenTlili]

@palagonKevo it looks like a compatibility issue with React 19. I downgraded React to 18 in your codesandbox example and it worked fine.

[palagonKevo]

Ok. I found a way to avoid using the eventWrapper in my use case, and I'll use that until this is fixed. At least is working somehow, but it would be great to know a way to solve this, I want to use the latest version to get the latest features.

[palagonKevo]

Any fix to this issue? It's still not working with react 19, and I can't use the latest features without updating.

[palagonKevo]

There's still a bug with React 19 related with the DnD. If you add an eventWrapper won't work. Moreover, onDropFromOutside event has stop working for other view than month view, and is not showing the "resource" variable when it's dropped within a resource.

And now there's this particular error, that seems to be new, and has stopped working for even older versions when you drop in day/week view:

[dmitrydidi]

hey, same boat on react v19, passing eventWrapper crashes the app with a same error

[palagonKevo]

I'm swapping to fullcalendar until this bugs are fixed. Those are critical for me, and fullcalendar seems to perform better.

[victoragcosta]

Same was happening with me a second ago and I've just updated to version 1.19.4 and the problem seem solved. I recommend you guys try updating and testing to see if the bug was incidentally fixed