TypeError: array_key_exists(): Argument #2 ($array) must be of type array, null given

Problem/Motivation

The issue is only reproducible after applying the core patch https://www.drupal.org/project/drupal/issues/3032353#comment-15746970 ✨ Exposed forms in a block are not currently updated when Ajax filtering is executed Needs work . There is no need for this fix until the linked patch is merged. However, having an additional type check for the variable that fixes the issue shouldn't harm as well.

Here is the error message.

The website encountered an unexpected error. Try again later.

TypeError: array_key_exists(): Argument #2 ($array) must be of type array, null given in Drupal\date_filter\Plugin\views\filter\DateBase->valueForm() (line 196 of modules/contrib/date_filter/src/Plugin/views/filter/DateBase.php).

Steps to reproduce

To reproduce the issue,

• Have drupal running with date_filter, better_exposed_filters module installed and enabled
• Create a content view with date filter added
• In the view configuration, use AJAX > Yes; Exposed form in block > Yes; Exposed form style > Better exposed filters; BEF settings > Uncheck Always show reset button; Configure some date filters e.g. for authored on;
• Render the exposed form block in view listing page
• When the linked patch is added, make some changes to filter, the Reset button should appear after filter is applied
• Try to Reset and check in browser console for error

Proposed resolution

Type check for $filter_input before calling array_key_exists() could be enough.
E.g.

-      \array_key_exists('date', $filter_input)
+      (\is_array($filter_input) && \array_key_exists('date', $filter_input))