Calendar not clickable when wrapped with shadow-dom - Removal of react-onclickoutside reintroduces bug

[gunavata]

Describe the bug
When upgrading to version v7.4.0, react-onclickoutside has been removed as part of this release:
#4979

This however will reintroduce an old bug from here:
#1928

Specifically, when the datepicker is open, clicking anywhere, including trying to click the datepicker popup content's itself, will automatically close the datepicker pop up without registering the click.

To Reproduce
Steps to reproduce the behavior:

1. Install version 7.4.0 of react-datepicker
2. Create a shadow root component
3. Insert a general Datepicker component with minimal setup i.e selected + onchange handler inside the shadow root component
4. Open the datepicker by clicking it
5. Attempt to click anything inside the datepicker popup (NOK -> will close the datepicker popup on a "mousedown" event)

Expected behavior
Datepicker pop up should not close on a mousedown event and should instead register the click appropriately.

Screenshots
Example datepicker:

Example render:

Example html:

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome
• Version: 129.0.6668.71 (Official Build) (32-bit)

Smartphone (please complete the following information):

NA

Additional context
Downgrading to v7.3.0, the datepicker works fine. Only present in v7.4.0

[DioEraclea]

Updated react-datepicker in our project to 7.5.0 and encountered the same issue.

[hamidrezahanafi]

@gunavata I originally removed it because react-onclickoutside is not going to be compatible with React 19
If you can give me a reproduction example, I will take a look

[robmisasi]

@hamidrezahanafi Here is a codesandbox reproducing this issue. I face this issue as well. The CSS is not applied under the shadowroot, but you can still attempt to click the buttons to show the behavior described above.