Issue #2204325 followup by Arla: Fixed The "rendered entity" formatter breaks for entity types with out a ViewBuilder.

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

@@ -112,10 +112,11 @@ class FormatterPluginManager extends DefaultPluginManager {
     $plugin_id = $configuration['type'];
 
     // Switch back to default formatter if either:
-    // - $type_info doesn't exist (the widget type is unknown),
-    // - the field type is not allowed for the widget.
+    // - the configuration does not specify a formatter class
+    // - the field type is not allowed for the formatter
+    // - the formatter is not applicable to the field definition.
     $definition = $this->getDefinition($configuration['type'], FALSE);
-    if (!isset($definition['class']) || !in_array($field_type, $definition['field_types'])) {
+    if (!isset($definition['class']) || !in_array($field_type, $definition['field_types']) || !$definition['class']::isApplicable($field_definition)) {
       // Grab the default widget for the field type.
       $field_type_definition = $this->fieldTypeManager->getDefinition($field_type);
       if (empty($field_type_definition['default_formatter'])) {

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

@@ -98,10 +98,11 @@ class WidgetPluginManager extends DefaultPluginManager {
     $plugin_id = $configuration['type'];
 
     // Switch back to default widget if either:
-    // - $type_info doesn't exist (the widget type is unknown),
-    // - the field type is not allowed for the widget.
+    // - the configuration does not specify a widget class
+    // - the field type is not allowed for the widget
+    // - the widget is not applicable to the field definition.
     $definition = $this->getDefinition($configuration['type'], FALSE);
-    if (!isset($definition['class']) || !in_array($field_type, $definition['field_types'])) {
+    if (!isset($definition['class']) || !in_array($field_type, $definition['field_types']) || !$definition['class']::isApplicable($field_definition)) {
       // Grab the default widget for the field type.
       $field_type_definition = $this->fieldTypeManager->getDefinition($field_type);
       if (empty($field_type_definition['default_widget'])) {

core/modules/field/src/Tests/FormatterPluginManagerTest.php

@@ -0,0 +1,52 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\field\Tests\FormatterPluginManagerTest.
+ */
+
+namespace Drupal\field\Tests;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Field\FormatterPluginManager;
+
+/**
+ * Tests the field formatter plugin manager.
+ *
+ * @group field
+ */
+class FormatterPluginManagerTest extends FieldUnitTestBase {
+
+  /**
+   * Tests that getInstance falls back on default if current is not applicable.
+   *
+   * @see \Drupal\field\Tests\WidgetPluginManagerTest::testNotApplicableFallback()
+   */
+  public function testNotApplicableFallback() {
+    /** @var FormatterPluginManager $formatter_plugin_manager */
+    $formatter_plugin_manager = \Drupal::service('plugin.manager.field.formatter');
+
+    $base_field_definition = BaseFieldDefinition::create('test_field')
+      // Set a name that will make isApplicable() return TRUE.
+      ->setName('field_test_field');
+
+    $formatter_options = array(
+      'field_definition' => $base_field_definition,
+      'view_mode' => 'default',
+      'configuration' => array(
+        'type' => 'field_test_applicable',
+      ),
+    );
+
+    $instance = $formatter_plugin_manager->getInstance($formatter_options);
+    $this->assertEqual($instance->getPluginId(), 'field_test_applicable');
+
+    // Now set name to something that makes isApplicable() return FALSE.
+    $base_field_definition->setName('deny_applicable');
+    $instance = $formatter_plugin_manager->getInstance($formatter_options);
+
+    // Instance should be default widget.
+    $this->assertNotEqual($instance->getPluginId(), 'field_test_applicable');
+    $this->assertEqual($instance->getPluginId(), 'field_test_default');
+  }
+
+}

core/modules/field/src/Tests/WidgetPluginManagerTest.php

@@ -2,10 +2,12 @@
 
 /**
  * @file
- * Contains \Drupal\field\Tests\WidgetManagerTest.
+ * Contains \Drupal\field\Tests\WidgetPluginManagerTest.
  */
 
 namespace Drupal\field\Tests;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Field\WidgetPluginManager;
 
 /**
  * Tests the field widget manager.
@@ -20,8 +22,42 @@ class WidgetPluginManagerTest extends FieldUnitTestBase {
   function testWidgetDefinitionAlter() {
     $widget_definition = \Drupal::service('plugin.manager.field.widget')->getDefinition('test_field_widget_multiple');
 
-    // Test if hook_field_widget_info_alter is beïng called.
+    // Test if hook_field_widget_info_alter is being called.
     $this->assertTrue(in_array('test_field', $widget_definition['field_types']), "The 'test_field_widget_multiple' widget is enabled for the 'test_field' field type in field_test_field_widget_info_alter().");
   }
 
+  /**
+   * Tests that getInstance falls back on default if current is not applicable.
+   *
+   * @see \Drupal\field\Tests\FormatterPluginManagerTest::testNotApplicableFallback()
+   */
+  public function testNotApplicableFallback() {
+    /** @var WidgetPluginManager $widget_plugin_manager */
+    $widget_plugin_manager = \Drupal::service('plugin.manager.field.widget');
+
+    $base_field_definition = BaseFieldDefinition::create('test_field')
+      // Set a name that will make isApplicable() return TRUE.
+      ->setName('field_multiwidgetfield');
+
+    $widget_options = array(
+      'field_definition' => $base_field_definition,
+      'form_mode' => 'default',
+      'configuration' => array(
+        'type' => 'test_field_widget_multiple',
+      ),
+    );
+
+    $instance = $widget_plugin_manager->getInstance($widget_options);
+    $this->assertEqual($instance->getPluginId(), 'test_field_widget_multiple');
+
+    // Now do the same but with machine name field_onewidgetfield, because that
+    // makes isApplicable() return FALSE.
+    $base_field_definition->setName('field_onewidgetfield');
+    $instance = $widget_plugin_manager->getInstance($widget_options);
+
+    // Instance should be default widget.
+    $this->assertNotEqual($instance->getPluginId(), 'test_field_widget_multiple');
+    $this->assertEqual($instance->getPluginId(), 'test_field_widget');
+  }
+
 }

core/modules/field/tests/modules/field_test/src/Plugin/Field/FieldFormatter/TestFieldApplicableFormatter.php

@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\field_test\Plugin\Field\FieldFormatter\TestFieldApplicableFormatter.
+ */
+
+namespace Drupal\field_test\Plugin\Field\FieldFormatter;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FormatterBase;
+
+
+/**
+ * Plugin implementation of the 'field_test_applicable' formatter.
+ *
+ * It is applicable to test_field fields unless their name is 'deny_applicable'.
+ *
+ * @FieldFormatter(
+ *   id = "field_test_applicable",
+ *   label = @Translation("Applicable"),
+ *   description = @Translation("Applicable formatter"),
+ *   field_types = {
+ *     "test_field"
+ *   },
+ *   weight = 15,
+ * )
+ */
+class TestFieldApplicableFormatter extends FormatterBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function isApplicable(FieldDefinitionInterface $field_definition) {
+    return $field_definition->getName() != 'deny_applicable';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewElements(FieldItemListInterface $items) {
+    return array('#markup' => 'Nothing to see here');
+  }
+}

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

@@ -66,6 +66,7 @@ class ManageDisplayTest extends FieldUiTestBase {
       'field_test_default',
       'field_test_multiple',
       'field_test_with_prepare_view',
+      'field_test_applicable',
       'hidden',
     );
     $this->assertEqual($options, $expected_options, 'The expected formatter ordering is respected.');