TypeError: array_keys(): Argument #1 ($array) must be of type array, null given in array_keys() (line 258 of /code/modules/contrib/better_exposed_filters/src/Plugin/better_exposed_filters/filter/FilterWidgetBase.php).

OK, I've narrowed down the issue (in my case) to exposed date filter using the "between" operator.
The wrapper-handling logic in FilterWidgetBase is choking. Not sure how widely this applies otherwise.

Here's a test that should fail to demonstrate the issue.
Will follow up with a one-liner to fix.

In this patch:
- Add a field "bef_date" to the "bef_test" content type
- Add the field as an exposed filter on the "bef_test" view

Observed behavior:
Fatal error when loading the view, because of the error referenced in title.

Test was failing, but for the wrong reason.
I forgot simpletest doesn't know how to figure out dependencies.
Added "datetime" to the test modules, should give the appropriate result.

Interesting, seems like this is only an issue for D10.
But BEF builds are failing tests for D10, so I can't provide a test to demonstrate the failure.

Once builds are passing on D10, we should revisit the tests.

In the meantime, the MR is a one-liner that fixes the issue for me.

I wasn't able to replicate this issue.

Did you try adding a datetime field, and datetime exposed filter with "between" operator?
I have replicated it consistently on a vanilla D10.1 install.

Updated OP and title

I tested this on a 10.0.x Drupal installation and couldn't replicate this, I'll try on a D10.1.x and see

Tried replicate on 6.0.x and 10.3.x but not able to replicate, is this still an issue?

Doesn't seem like it's still happening, but let's see what testbot says.

Here's a re-roll of the TEST-ONLY patch against latest dev.

So just FYI gitlab has a test-only feature so you don't need to do test-only patches. Plus drupalCI is wildly behind and soon to be shutdown.

Yeah, I did see that - very cool!

Looks like BEF tests are failing, but this one passes, so ... i assume that's a known issue and this is closeable.
https://git.drupalcode.org/issue/better_exposed_filters-3393662/-/jobs/1304335

smustgrave → closed merge request !48

I still have this on the latest version. I'm adding the exposed filter programmatically, if that matters. Commenting mostly to change the version number.