Field groups are not copied when cloning display

I can confirm indeed the variable is never defined!

So it will always be unset here without the fix:

if (!isset($destination_bundle_field_names[$child_field])) {
  unset($group_settings['children'][$index]);
}

Where I'm not sure is, if the $destination_bundle_field_names = $destination_display->getComponents(); should be inside the field_groups condition?

Setting priority to major as this is a clear code bug which breaks expected (and existing) functionality.

+++ b/src/DisplayCloner.php
@@ -113,6 +113,8 @@ class DisplayCloner {
+    $destination_bundle_field_names = $destination_display->getComponents();

getComponents() does not return field names!

@joachim Is naming only issue you have with this?

That's how it is named in module currently only variable init is missing, I guess it went missing in some point

I will create new patch..

Just ran into this again, so I'll try to place this on our agenda.

I can confirm that the patch fixes the issue! Very weird, that the variable declaration of

$destination_bundle_field_names

was somehow removed.

I applied @holo96's patch as an MR and renamed the variable, please review!

Thank you @Grevil, that's indeed a crazy reason for the bug ;D

I think the fixes are okay, as it's not too many. RTBC! Would be great to have this fixed and Field groups support back again!