Issue #3485452 by riyas_nr, mjmorley, smustgrave: Datetime fields should utilise #required_error

core/lib/Drupal/Core/Datetime/Element/Datetime.php

@@ -357,8 +357,13 @@ public static function validateDatetime(&$element, FormStateInterface $form_stat
       // If there's empty input and the field is required, set an error. A
       // reminder of the required format in the message provides a good UX.
       elseif (empty($input['date']) && empty($input['time']) && $element['#required']) {
+        if (isset($element['#required_error'])) {
+          $form_state->setError($element, $element['#required_error']);
+        }
+        else {
           $form_state->setError($element, t('The %field date is required.', ['%field' => $title]));
         }
+      }
       else {
         // If the date is valid, set it.
         $date = $input['object'];

core/tests/Drupal/KernelTests/Core/Datetime/DatetimeElementFormTest.php

@@ -99,6 +99,29 @@ public function buildForm(array $form, FormStateInterface $form_state, string $d
       '#date_time_element' => 'HTML Time',
     ];
 
+    // Element with #required_error.
+    $form['datetime_required_error'] = [
+      '#type' => 'datetime',
+      '#title' => 'Datetime with required error',
+      '#date_date_format' => 'Y-m-d',
+      '#date_time_format' => 'H:i:s',
+      '#date_date_element' => 'HTML Date',
+      '#date_time_element' => 'HTML Time',
+      '#required' => TRUE,
+      '#required_error' => 'Custom required error message.',
+    ];
+
+    // Element without #required_error.
+    $form['datetime_no_required_error'] = [
+      '#type' => 'datetime',
+      '#title' => 'Datetime without required error',
+      '#date_date_format' => 'Y-m-d',
+      '#date_time_format' => 'H:i:s',
+      '#date_date_element' => 'HTML Date',
+      '#date_time_element' => 'HTML Time',
+      '#required' => TRUE,
+    ];
+
     $form['submit'] = [
       '#type' => 'submit',
       '#value' => 'Submit',
@@ -210,4 +233,29 @@ public static function trustedCallbacks() {
     ];
   }
 
+  /**
+   * Tests the custom required error message for datetime elements.
+   */
+  public function testDatetimeElementRequiredError(): void {
+    $form_builder = $this->container->get('form_builder');
+
+    // Test datetime element with #required_error.
+    $form_state = (new FormState())
+      ->setValues([
+        'datetime_required_error' => '',
+      ]);
+    $form_builder->submitForm($this, $form_state);
+    // Check that the custom required error message is set correctly.
+    $this->assertEquals('Custom required error message.', $form_state->getErrors()['datetime_required_error']);
+
+    // Test datetime element without #required_error.
+    $form_state = (new FormState())
+      ->setValues([
+        'datetime_no_required_error' => '',
+      ]);
+    $form_builder->submitForm($this, $form_state);
+    // Check that the default required error message is set correctly.
+    $this->assertEquals('The Datetime without required error date is required.', $form_state->getErrors()['datetime_no_required_error']);
+  }
+
 }