Issue #3206256: Ability to mark options as required

src/OptionBase.php

@@ -37,7 +37,7 @@ abstract class OptionBase extends PluginBase implements OptionInterface {
    * @var array
    */
   protected $optionalAttributes =
-    ['weight', 'allowed_regions'];
+    ['required', 'weight', 'allowed_regions'];
 
   /**
    * {@inheritdoc}
@@ -316,6 +316,9 @@ abstract class OptionBase extends PluginBase implements OptionInterface {
       '#type' => 'textfield',
       '#default_value' => !empty($default) ? $default : '',
     ];
+    if (isset($def['required'])) {
+      $formRenderArray['#required'] = $def['required'];
+    }
     if (isset($def['weight'])) {
       $formRenderArray['#weight'] = $def['weight'];
     }
@@ -361,13 +364,19 @@ abstract class OptionBase extends PluginBase implements OptionInterface {
       '#type' => 'select',
       // @phpstan-ignore-next-line
       '#options' => $this->translateOptions($def['options']),
-      '#empty_option' => $this->t('- None -'),
-      '#empty_value' => '',
       '#default_value' => $default,
     ];
     if ($def['multi']) {
       $formRenderArray['#multiple'] = TRUE;
     }
+    if (isset($def['required'])) {
+      $formRenderArray['#required'] = $def['required'];
+    }
+    else {
+      $emptyOption = !empty($def['empty_option']) ? $def['empty_option'] : '- None -';
+      $formRenderArray['#empty_option'] = $this->t($emptyOption);
+      $formRenderArray['#empty_value'] = '';
+    }
     if (isset($def['weight'])) {
       $formRenderArray['#weight'] = $def['weight'];
     }
@@ -418,6 +427,9 @@ abstract class OptionBase extends PluginBase implements OptionInterface {
     if ($def['inline']) {
       $formRenderArray['#attributes'] = ['class' => ['container-inline']];
     }
+    if (isset($def['required'])) {
+      $formRenderArray['#required'] = $def['required'];
+    }
     if (isset($def['weight'])) {
       $formRenderArray['#weight'] = $def['weight'];
     }
@@ -468,6 +480,9 @@ abstract class OptionBase extends PluginBase implements OptionInterface {
     if ($def['inline']) {
       $formRenderArray['#attributes'] = ['class' => ['container-inline']];
     }
+    if (isset($def['required'])) {
+      $formRenderArray['#required'] = $def['required'];
+    }
     if (isset($def['weight'])) {
       $formRenderArray['#weight'] = $def['weight'];
     }

[Florent Torregrosa]

empty_option and empty_value should not be related to require. This is handled in the select render element.

Also if no empty_option is provided do not set it and then it will rely on the render element default behavior.