Issue #2395613 by dawehner: Make it possible to configure the output of a boolean field on the formatter level

core/config/schema/core.entity.schema.yml

@@ -222,6 +222,19 @@ field.widget.settings.checkbox:
       type: boolean
       label: 'Use field label instead of the "On value" as label'
 
+field.formatter.settings.boolean:
+  type: mapping
+  mapping:
+    format:
+      type: string
+      label: 'Output format'
+    format_custom_false:
+      type: string
+      label: 'Custom output for FALSE'
+    format_custom_true:
+      type: string
+      label: 'Custom output for TRUE'
+
 field.formatter.settings.string:
   type: mapping
   mapping:

core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/BooleanFormatter.php

@@ -9,6 +9,7 @@ namespace Drupal\Core\Field\Plugin\Field\FieldFormatter;
 
 use Drupal\Core\Field\FormatterBase;
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Plugin implementation of the 'boolean' formatter.
@@ -23,14 +24,107 @@ use Drupal\Core\Field\FieldItemListInterface;
  */
 class BooleanFormatter extends FormatterBase {
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    $settings = [];
+
+    // Fall back to field settings by default.
+    $settings['format'] = 'default';
+    $settings['format_custom_false'] = '';
+    $settings['format_custom_true'] = '';
+
+    return $settings;
+  }
+
+  /**
+   * Gets the available format options.
+   *
+   * @return array|string
+   *   A list of output formats. Each entry is keyed by the machine name of the
+   *   format. The value is an array, of which the first item is the result for
+   *   boolean TRUE, the second is for boolean FALSE. The value can be also an
+   *   array, but this is just the case for the custom format.
+   */
+  protected function getOutputFormats() {
+    $formats = [
+      'default' => [$this->getFieldSetting('on_label'), $this->getFieldSetting('off_label')],
+      'yes-no' => [$this->t('Yes'), $this->t('No')],
+      'true-false' => [$this->t('True'), $this->t('False')],
+      'on-off' => [$this->t('On'), $this->t('Off')],
+      'enabled-disabled' => [$this->t('Enabled'), $this->t('Disabled')],
+      'boolean' => [1, 0],
+      'unicode-yes-no' => ['✔', '✖'],
+      'custom' => $this->t('Custom'),
+    ];
+
+    return $formats;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    $form = parent::settingsForm($form, $form_state);
+
+    $formats = [];
+    foreach ($this->getOutputFormats() as $format_name => $format) {
+      if (is_array($format)) {
+        $formats[$format_name] = implode(' / ', $format);
+      }
+      else {
+        $formats[$format_name] = $format;
+      }
+    }
+
+    $form['format'] = [
+      '#type' => 'select',
+      '#title' => $this->t('Output format'),
+      '#default_value' => $this->getSetting('format'),
+      '#options' => $formats,
+    ];
+    $form['format_custom_true'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Custom output for TRUE'),
+      '#default_value' => $this->getSetting('format_custom_true'),
+      '#states' => [
+        'visible' => [
+          'select[name="fields[field_boolean][settings_edit_form][settings][format]"]' => ['value' => 'custom'],
+        ],
+      ],
+    ];
+    $form['format_custom_false'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Custom output for FALSE'),
+      '#default_value' => $this->getSetting('format_custom_false'),
+      '#states' => [
+        'visible' => [
+          'select[name="fields[field_boolean][settings_edit_form][settings][format]"]' => ['value' => 'custom'],
+        ],
+      ],
+    ];
+
+    return $form;
+  }
+
   /**
    * {@inheritdoc}
    */
   public function viewElements(FieldItemListInterface $items) {
-    $elements = array();
+    $elements = [];
+
+    $formats = $this->getOutputFormats();
 
     foreach ($items as $delta => $item) {
-      $elements[$delta] = array('#markup' => $item->value ? $this->getFieldSetting('on_label') : $this->getFieldSetting('off_label'));
+      $format = $this->getSetting('format');
+
+      if ($format == 'custom') {
+        $elements[$delta] = ['#markup' => $item->value ? $this->getSetting('format_custom_true') : $this->getSetting('format_custom_false')];
+      }
+      else {
+        $elements[$delta] = ['#markup' => $item->value ? $formats[$format][0] : $formats[$format][1]];
+      }
     }
 
     return $elements;

core/modules/field/src/Tests/Boolean/BooleanFormatterTest.php

@@ -0,0 +1,144 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\field\Tests\Boolean\BooleanFormatterTest.
+ */
+
+namespace Drupal\field\Tests\Boolean;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+use Drupal\Core\Entity\FieldableEntityInterface;
+use Drupal\entity_test\Entity\EntityTest;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests the boolean formatter.
+ *
+ * @group field
+ */
+class BooleanFormatterTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['field', 'text', 'entity_test', 'user'];
+
+  /**
+   * @var string
+   */
+  protected $entityType;
+
+  /**
+   * @var string
+   */
+  protected $bundle;
+
+  /**
+   * @var string
+   */
+  protected $fieldName;
+
+  /**
+   * @var \Drupal\Core\Entity\Display\EntityViewDisplayInterface
+   */
+  protected $display;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->installConfig(['field']);
+    $this->installEntitySchema('entity_test');
+
+    $this->entityType = 'entity_test';
+    $this->bundle = $this->entityType;
+    $this->fieldName = Unicode::strtolower($this->randomMachineName());
+
+    $field_storage = FieldStorageConfig::create([
+      'field_name' => $this->fieldName,
+      'entity_type' => $this->entityType,
+      'type' => 'boolean',
+    ]);
+    $field_storage->save();
+
+    $instance = FieldConfig::create([
+      'field_storage' => $field_storage,
+      'bundle' => $this->bundle,
+      'label' => $this->randomMachineName(),
+    ]);
+    $instance->save();
+
+    $this->display = entity_get_display($this->entityType, $this->bundle, 'default')
+      ->setComponent($this->fieldName, [
+        'type' => 'boolean',
+        'settings' => [],
+      ]);
+    $this->display->save();
+  }
+
+  /**
+   * Renders fields of a given entity with a given display.
+   *
+   * @param \Drupal\Core\Entity\FieldableEntityInterface $entity
+   *   The entity object with attached fields to render.
+   * @param \Drupal\Core\Entity\Display\EntityViewDisplayInterface $display
+   *   The display to render the fields in.
+   *
+   * @return string
+   *   The rendered entity fields.
+   */
+  protected function renderEntityFields(FieldableEntityInterface $entity, EntityViewDisplayInterface $display) {
+    $content = $display->build($entity);
+    $content = $this->render($content);
+    return $content;
+  }
+
+  /**
+   * Tests boolean formatter output.
+   */
+  public function testBooleanFormatter() {
+    $data = [];
+    $data[] = [0, [], 'Off'];
+    $data[] = [1, [], 'On'];
+
+    $format = ['format' => 'enabled-disabled'];
+    $data[] = [0, $format, 'Disabled'];
+    $data[] = [1, $format, 'Enabled'];
+
+    $format = ['format' => 'unicode-yes-no'];
+    $data[] = [1, $format, '✔'];
+    $data[] = [0, $format, '✖'];
+
+    $format = [
+      'format' => 'custom',
+      'format_custom_false' => 'FALSE',
+      'format_custom_true' => 'TRUE'
+    ];
+    $data[] = [0, $format, 'FALSE'];
+    $data[] = [1, $format, 'TRUE'];
+
+    foreach ($data as $test_data) {
+      list($value, $settings, $expected) = $test_data;
+
+      $component = $this->display->getComponent($this->fieldName);
+      $component['settings'] = $settings;
+      $this->display->setComponent($this->fieldName, $component);
+
+      $entity = EntityTest::create([]);
+      $entity->{$this->fieldName}->value = $value;
+
+      // Verify that all HTML is escaped and newlines are retained.
+      $this->renderEntityFields($entity, $this->display);
+      $this->assertRaw($expected);
+    }
+  }
+
+}