Deprecated function: preg_match(): Passing null to parameter #2 ($subject)

Working on it.

The remaining test failures don't appear to be related to the datetimeRangeYears() fix.

Fixes need to land in 11.x first. But what's the scenario where these values are missing, may require test coverage.

Hey @smustgrave, please let me know if you want any other changes.

Still need concrete steps as I’m not seeing this

Steps to Reproduce

Create a custom form that includes a datetime field.
Set both default_value and date_year_range to an empty string.

Use the following example code:

<?php

declare(strict_types=1);

namespace Drupal\my_module\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;

/**
 * Provides a My Module form.
 */
final class ExampleForm extends FormBase {

  /**
   * {@inheritdoc}
   */
  public function getFormId(): string {
    return 'my_module_example';
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state): array {
    // Reproduce the bug by passing an empty string or invalid format.
    // The issue occurs when datetimeRangeYears() receives a malformed string.
    $form['date_field'] = [
      '#type' => 'datetime',
      '#title' => $this->t('Date'),
      '#date_year_range' => '',  // Empty string triggers the bug
      '#default_value' => new \Drupal\Core\Datetime\DrupalDateTime('2024-01-01'),
    ];

    $form['actions'] = [
      '#type' => 'actions',
      'submit' => [
        '#type' => 'submit',
        '#value' => $this->t('Send'),
      ],
    ];

    return $form;
  }

}

Visit the form page in the browser.

Observe the URL — the malformed date_year_range value causes the issue.

Okay why would you do that though?

Let me elaborate more. Not knocking the code snippet at all. But is it a valid scenario?

I could write faulty code that could break things and that would be on me not the system to handle.

If a valid scenario a test case should be added

For testing I found this: core/tests/Drupal/KernelTests/Core/Datetime/Element/DatetimeFormElementTest.php. Lines 84 to 89 seem useful.

  /**
   * Checks we have no errors on form submit.
   *
   * @legacy-covers ::validateDatetime
   */
  public function testNoErrorMetOnFormSubmit(): void {
    // No error expected when form elements have no value.

As I understand it the error in this issue occurs when one of the datetime fields is left blank? And the error occurs on form submission?

Would be helpful to get 'steps to reproduce' in the IS.

Agree with #14
I am not sure it counts as a valid scenario, but I can think of something like this. Honestly, I can't think of any other valid scenario.

    $config = $this->config('my_module.settings');
    $year_range = $config->get('date_year_range'); // Returns NULL if not set
    $form['date_field'] = [
      '#type' => 'datelist',
      '#title' => $this->t('Select Date'),
      '#date_year_range' => $year_range, // NULL triggers deprecation
    ];
    ];