Undefined array key 'delete' if user does not have permission to delete the entity

For reference, this is reproducible only if the user does not have the access to delete the entity removed. In web/modules/contrib/inline_entity_form/src/Plugin/Field/FieldWidget/InlineEntityFormComplex.php:914 there is a check already

    if (!empty($entity_id) && $this->getSetting('removed_reference') === self::REMOVED_OPTIONAL && $entity->access('delete')) {

and the delete checkbox is not added if the user does not have 'delete' access. This, checking either for the access or if the array key exists is a valid case.
I don't know if tests are needed as this is a warning and a simple missing check that does not affect the end result. The user does not have access, the entity is also not marked for deletion.

Thx a lot, this makes a lot of sense.

But code is overly complex. Please use the more idiomatic !empty($form_values['delete'])

@geek-merlin I simplified the code as suggested in #5. So I guess this can be merged.

I added a variable for the if() statement to make it clearer what the intent is. I also added a kernel test.

Thank you, LGTM!

Thanks for working on this! Especially thanks @bluegeek9 for the Kernel test. I confirmed locally it fails without the fix applied. Can also see it at https://git.drupalcode.org/project/inline_entity_form/-/jobs/10122967 in the last pipeline.

I pushed a commit to try to improve the readability of the if statement. I ran the full pipeline on all versions of core, and everything is green: https://git.drupalcode.org/project/inline_entity_form/-/pipelines/837497

Merged to 3.x.

Thanks again!
-Derek

Thank YOU very much @dww for merging all these changes now! Very important, thanks!