Issue #2354685 by amateescu, tstoeckler, derhasi: Fatal Error on re-saving required EntityReference field setting

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

@@ -334,6 +334,9 @@ class FieldItemList extends ItemList implements FieldItemListInterface {
     // Extract the submitted value, and validate it.
     $widget = $this->defaultValueWidget($form_state);
     $widget->extractFormValues($this, $element, $form_state);
+    // Force a non-required field definition.
+    // @see self::defaultValueWidget().
+    $this->definition->required = FALSE;
     $violations = $this->validate();
 
     // Assign reported errors to the correct form element.

core/modules/entity_reference/src/Tests/EntityReferenceAdminTest.php

@@ -103,11 +103,18 @@ class EntityReferenceAdminTest extends WebTestBase {
 
     // Third step: confirm.
     $this->drupalPostForm(NULL, array(
+      'field[required]' => '1',
       'field[settings][handler_settings][target_bundles][' . key($bundles) . ']' => key($bundles),
     ), t('Save settings'));
 
     // Check that the field appears in the overview form.
     $this->assertFieldByXPath('//table[@id="field-overview"]//tr[@id="field-test"]/td[1]', 'Test label', 'Field was created and appears in the overview page.');
+
+    // Check that the field settings form can be submitted again, even when the
+    // field is required.
+    // The first 'Edit' link is for the Body field.
+    $this->clickLink(t('Edit'), 1);
+    $this->drupalPostForm(NULL, array(), t('Save settings'));
   }
 
 

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

@@ -359,6 +359,24 @@ class ManageFieldsTest extends WebTestBase {
     $field = FieldConfig::loadByName('node', $this->type, $field_name);
     $this->assertEqual($field->default_value, NULL, 'The default value was correctly saved.');
 
+    // Check that the default value can be empty when the field is marked as
+    // required and can store unlimited values.
+    $field_storage = FieldStorageConfig::loadByName('node', $field_name);
+    $field_storage->cardinality = FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED;
+    $field_storage->save();
+
+    $this->drupalGet($admin_path);
+    $edit = array(
+      'field[required]' => 1,
+    );
+    $this->drupalPostForm(NULL, $edit, t('Save settings'));
+
+    $this->drupalGet($admin_path);
+    $this->drupalPostForm(NULL, array(), t('Save settings'));
+    $this->assertText("Saved $field_name configuration", 'The form was successfully submitted.');
+    $field = FieldConfig::loadByName('node', $this->type, $field_name);
+    $this->assertEqual($field->default_value, NULL, 'The default value was correctly saved.');
+
     // Check that the default widget is used when the field is hidden.
     entity_get_form_display($field->entity_type, $field->bundle, 'default')
       ->removeComponent($field_name)->save();