Date filter shows error in view exposed group filter with multiple select option

I was able to reproduce the issue and your fix solves the problem for me.

Patch for 10.0.x branch.

Nice find.

Something similar was happening in #2811887: Exposed date filter leads to a notice, we should add test coverage here too.

**maybe** duplicate of #3178117: Views exposed group filter (with option allow multiple selections) generates notices when using date and date range fields ?

Made few changes on top of the MR. I will update the test cases as well.

Patch of #11

After applying the patch of #7 (which fixed the 'type' issue, well done.) I found this error:

Warning: Undefined array key "value" in Drupal\views\Plugin\views\filter\Date->acceptExposedInput() (line 153 of /var/www/html/web/core/modules/views/src/Plugin/views/filter/Date.php)

Looking into the code it seems that $operators[$operator]['values'] can be 1 without $this->value['value'] being set.

Perhaps we can add an isset test to the if statement in this block like:

if (!isset($this->value['value']) || $this->value['value'] == '') {
    return FALSE;
}

I'm suggesting this as a todo for you, as you already have the code and the existing patch available to you for tweaking. If it's preferable for me to try putting the combined patch together I can give it a shot. I hope this isn't too much of an imposition on your time.

This issue happened on my end; this is the view I tested: test_expose_date_filter.yml or please see my screenshot

I applied a patch and added a test case for this issue.

Removing tests tag as coverage appears to be there.

Left some comments on the MR but proposed solution doesn't match the MR

The proposed fix here overlaps with the one in #3389478: Views exposed filter warnings on Date filter min & max.

I have another use case that triggers PHP warning here.

Steps to reproduce
Install Drupal standard profile

1. Edit the default Content view at /admin/structure/views/view/content
2. Add a "Created" filter
3. Select "Expose this filter to visitors, to allow them to change it"
4. Select "Grouped filters"
5. Set the Grouping 1 label to "Past Month", operator to "Is greater than or equal to", value type to "An offset from ..." and value "-30 days"
6. No not check "Allow multiple selections"
7. Press Apply and then Save
8. Navigate to /admin/content

Note: This may or may not require Search API and an index including the date field used by this filter.

Proposed resolution
Replace condition in the \Drupal\views\Plugin\views\filter\Date:155 (give or take a few lines in dev)
if (!empty($this->options['expose']['use_operator']) && !empty($this->options['expose']['operator_id'])) {
with

if (
  !empty($this->options['expose']['use_operator'])
  && !empty($this->options['expose']['operator_id'])
  && isset($input[$this->options['expose']['operator_id']])
) {

Again, this just a PHP warning that has only really started being flagged in PHP 8.

I've created a new MR that merges in to main, and brought everything up to date. I've hidden the older MRs for clarity.

Verified the bug on the latest main branch, following the steps in the summary.

Applying the MR the error does go away.

Test-only shows the issue (can't run in pipeline)

Behat\Mink\Exception\ElementNotFoundException: Button with id|name|label|value "Apply" not found.
/var/www/html/core/tests/Drupal/Tests/WebAssert.php:159
/var/www/html/core/tests/Drupal/Tests/UiHelperTrait.php:76
/var/www/html/core/modules/datetime/tests/src/Functional/Views/FilterDateTest.php:299

Left a few questions and summary proposed solution doesn't line up perfectly. Can that be cleaned up please

Looks super close.