Issue #2084987 by andypost, Jalandhar: Remove usage of field_ui_default_value...

Issue #2084987 by andypost, Jalandhar: Remove usage of field_ui_default_value and recommend proper replacement

core/lib/Drupal/Core/Field/WidgetBase.php

@@ -318,7 +318,7 @@ protected function formSingleElement(FieldItemListInterface $items, $delta, arra
         'widget' => $this,
         'items' => $items,
         'delta' => $delta,
-        'default' => !empty($entity->field_ui_default_value),
+        'default' => $this->isDefaultValueWidget($form_state),
       );
       \Drupal::moduleHandler()->alter(array('field_widget_form', 'field_widget_' . $this->getPluginId() . '_form'), $element, $form_state, $context);
     }
@@ -539,4 +539,17 @@ public static function isApplicable(FieldDefinitionInterface $field_definition)
     return TRUE;
   }
 
+  /**
+   * Returns whether the widget used for default value form.
+   *
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   *
+   * @return bool
+   *   TRUE if a widget used to input default value, FALSE otherwise.
+   */
+  protected function isDefaultValueWidget(FormStateInterface $form_state) {
+    return (bool) $form_state->get('default_value_widget');
+  }
+
 }

core/modules/field_ui/src/Tests/ManageFieldsTest.php

@@ -589,6 +589,11 @@ function testHelpDescriptions() {
     );
     $this->drupalPostForm('admin/structure/types/manage/article/fields/node.article.field_image', $edit, t('Save settings'));
 
+    // Check that hook_field_widget_form_alter() does believe this is the
+    // default value form.
+    $this->drupalGet('admin/structure/types/manage/article/fields/node.article.field_tags');
+    $this->assertText('From hook_field_widget_form_alter(): Default form is true.', 'Default value form in hook_field_widget_form_alter().');
+
     $edit = array(
       'field[description]' => '<em>Test with a non upload field.',
     );

core/modules/link/src/Plugin/Field/FieldWidget/LinkWidget.php

@@ -84,7 +84,7 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
     // Post-process the title field to make it conditionally required if URL is
     // non-empty. Omit the validation on the field edit form, since the field
     // settings cannot be saved otherwise.
-    if (!$form_state->get('default_value_widget') && $this->getFieldSetting('title') == DRUPAL_REQUIRED) {
+    if (!$this->isDefaultValueWidget($form_state) && $this->getFieldSetting('title') == DRUPAL_REQUIRED) {
       $element['#element_validate'][] = array($this, 'validateTitle');
     }