Issue #3382802 by srishtiiee, kunal.sachdev, marcoliver, ckrina: Disable the 'Remove' button if there is a single row in the allowed values storage setting of the list fields

core/modules/options/src/Plugin/Field/FieldType/ListItemBase.php

@@ -185,6 +185,10 @@ abstract class ListItemBase extends FieldItemBase implements OptionsProviderInte
         '#default_value' => 0,
         '#attributes' => ['class' => ['weight']],
       ];
+      // Disable the remove button if there is only one row in the table.
+      if ($max === 0) {
+        $element['allowed_values']['table'][0]['delete']['#attributes']['disabled'] = 'disabled';
+      }
       if ($delta < count($allowed_values)) {
         $query = \Drupal::entityQuery($entity_type_id)
           ->accessCheck(FALSE)
@@ -261,6 +265,10 @@ abstract class ListItemBase extends FieldItemBase implements OptionsProviderInte
     $delta = $element['table']['#max_delta'];
     $element['table'][$delta]['item']['#prefix'] = '<div class="ajax-new-content" data-drupal-selector="field-list-add-more-focus-target">' . ($element['table'][$delta]['item']['#prefix'] ?? '');
     $element['table'][$delta]['item']['#suffix'] = ($element['table'][$delta]['item']['#suffix'] ?? '') . '</div>';
+    // Enable the remove button for the first row if there are more rows.
+    if ($delta > 0 && isset($element['table'][0]['delete']['#attributes']['disabled']) && !isset($element['table'][0]['item']['key']['#attributes']['disabled'])) {
+      unset($element['table'][0]['delete']['#attributes']['disabled']);
+    }
 
     $response = new AjaxResponse();
     $response->addCommand(new InsertCommand(NULL, $element));

core/modules/options/tests/src/Functional/OptionsFieldUITest.php

@@ -454,8 +454,21 @@ class OptionsFieldUITest extends FieldTestBase {
       $this->createOptionsField($field_type);
       $page = $this->getSession()->getPage();
 
-      // Try to proceed without entering any value.
       $this->drupalGet($this->adminPath);
+      // Assert that the delete button for a single row is disabled.
+      $this->assertCount(1, $page->findAll('css', '#allowed-values-order tr.draggable'));
+      $delete_button_0 = $page->findById('remove_row_button__0');
+      $this->assertTrue($delete_button_0->hasAttribute('disabled'), 'Button is disabled');
+      $page->findButton('Add another item')->click();
+      // Assert that the delete button for the first row is enabled if there are
+      // more that one rows.
+      $this->assertCount(2, $page->findAll('css', '#allowed-values-order tr.draggable'));
+      $this->assertFalse($delete_button_0->hasAttribute('disabled'), 'Button is enabled');
+      // Delete a row.
+      $delete_button_0->click();
+      // Assert that the button is disabled again.
+      $this->assertTrue($delete_button_0->hasAttribute('disabled'), 'Button is disabled');
+      // Try to proceed without entering any value.
       $page->findButton('Save field settings')->click();
 
       if ($field_type == 'list_string') {