diff --git a/core/modules/entity_reference/entity_reference.module b/core/modules/entity_reference/entity_reference.module
index 6ad51f7dd80..7125faeb816 100644
--- a/core/modules/entity_reference/entity_reference.module
+++ b/core/modules/entity_reference/entity_reference.module
@@ -63,6 +63,18 @@ function entity_reference_entity_field_info_alter(&$info, $entity_type) {
   }
 }
 
+/**
+ * Implements hook_field_widget_info_alter().
+ */
+function entity_reference_field_widget_info_alter(&$info) {
+  if (isset($info['options_select'])) {
+    $info['options_select']['field_types'][] = 'entity_reference';
+  }
+  if (isset($info['options_buttons'])) {
+    $info['options_buttons']['field_types'][] = 'entity_reference';
+  }
+}
+
 /**
  * Gets the selection handler for a given entity_reference field.
  *
diff --git a/core/modules/options/lib/Drupal/options/Plugin/field/widget/ButtonsWidget.php b/core/modules/options/lib/Drupal/options/Plugin/field/widget/ButtonsWidget.php
new file mode 100644
index 00000000000..163f46c6773
--- /dev/null
+++ b/core/modules/options/lib/Drupal/options/Plugin/field/widget/ButtonsWidget.php
@@ -0,0 +1,76 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\options\Plugin\field\widget\ButtonsWidget.
+ */
+
+namespace Drupal\options\Plugin\field\widget;
+
+use Drupal\Component\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+
+/**
+ * Plugin implementation of the 'options_buttons' widget.
+ *
+ * @Plugin(
+ *   id = "options_buttons",
+ *   module = "options",
+ *   label = @Translation("Check boxes/radio buttons"),
+ *   field_types = {
+ *     "list_integer",
+ *     "list_float",
+ *     "list_text",
+ *     "list_boolean"
+ *   },
+ *   multiple_values = TRUE
+ * )
+ */
+class ButtonsWidget extends OptionsWidgetBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(array $items, $delta, array $element, $langcode, array &$form, array &$form_state) {
+    $element = parent::formElement($items, $delta, $element, $langcode, $form, $form_state);
+
+    $options = $this->getOptions();
+    $selected = $this->getSelectedOptions($items);
+
+    // If required and there is one single option, preselect it.
+    if ($this->required && count($options) == 1) {
+      reset($options);
+      $selected = array(key($options));
+    }
+
+    if ($this->multiple) {
+      $element += array(
+        '#type' => 'checkboxes',
+        '#default_value' => $selected,
+        '#options' => $options,
+      );
+    }
+    else {
+      $element += array(
+        '#type' => 'radios',
+        // Radio buttons need a scalar value. Take the first default value, or
+        // default to NULL so that the form element is properly recognized as
+        // not having a default value.
+        '#default_value' => $selected ? reset($selected) : NULL,
+        '#options' => $options,
+      );
+    }
+
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEmptyOption() {
+    if (!$this->required && !$this->multiple) {
+      return static::OPTIONS_EMPTY_NONE;
+    }
+  }
+
+}
diff --git a/core/modules/options/lib/Drupal/options/Plugin/field/widget/OnOffWidget.php b/core/modules/options/lib/Drupal/options/Plugin/field/widget/OnOffWidget.php
new file mode 100644
index 00000000000..7e6b4a599f2
--- /dev/null
+++ b/core/modules/options/lib/Drupal/options/Plugin/field/widget/OnOffWidget.php
@@ -0,0 +1,69 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\options\Plugin\field\widget\OnOffWidget.
+ */
+
+namespace Drupal\options\Plugin\field\widget;
+
+use Drupal\Component\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+
+/**
+ * Plugin implementation of the 'options_onoff' widget.
+ *
+ * @Plugin(
+ *   id = "options_onoff",
+ *   module = "options",
+ *   label = @Translation("Single on/off checkbox"),
+ *   field_types = {
+ *     "list_boolean"
+ *   },
+ *   settings = {
+ *     "display_label" = FALSE,
+ *   },
+ *   multiple_values = TRUE
+ * )
+ */
+class OnOffWidget extends OptionsWidgetBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, array &$form_state) {
+    $element['display_label'] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Use field label instead of the "On value" as label'),
+      '#default_value' => $this->getSetting('display_label'),
+      '#weight' => -1,
+    );
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(array $items, $delta, array $element, $langcode, array &$form, array &$form_state) {
+    $element = parent::formElement($items, $delta, $element, $langcode, $form, $form_state);
+
+    $options = $this->getOptions();
+    $selected = $this->getSelectedOptions($items);
+
+    $element += array(
+      '#type' => 'checkbox',
+      '#default_value' => !empty($selected[0]),
+    );
+
+    // Override the title from the incoming $element.
+    if ($this->getSetting('display_label')) {
+      $element['#title'] = $this->instance['label'];
+    }
+    else {
+      $element['#title'] = isset($options[1]) ? $options[1] : '';
+    }
+
+    return $element;
+  }
+
+}
diff --git a/core/modules/options/lib/Drupal/options/Plugin/field/widget/OptionsWidgetBase.php b/core/modules/options/lib/Drupal/options/Plugin/field/widget/OptionsWidgetBase.php
new file mode 100644
index 00000000000..40f24dfd948
--- /dev/null
+++ b/core/modules/options/lib/Drupal/options/Plugin/field/widget/OptionsWidgetBase.php
@@ -0,0 +1,206 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\options\Plugin\field\widget\OptionsWidgetBase.
+ */
+
+namespace Drupal\options\Plugin\field\widget;
+
+use Drupal\field\Plugin\Core\Entity\FieldInstance;
+use Drupal\field\Plugin\Type\Widget\WidgetBase;
+
+/**
+ * Base class for the 'options_*' widgets.
+ */
+abstract class OptionsWidgetBase extends WidgetBase {
+
+  /**
+   * Identifies a 'None' option.
+   */
+  const OPTIONS_EMPTY_NONE = 'option_none';
+
+  /**
+   * Identifies a 'Select a value' option.
+   */
+  const OPTIONS_EMPTY_SELECT = 'option_select';
+
+  /**
+   * Abstract over the actual field columns, to allow different field types to
+   * reuse those widgets.
+   *
+   * @var string
+   */
+  protected $column;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct($plugin_id, array $plugin_definition, FieldInstance $instance, array $settings, $weight) {
+    parent::__construct($plugin_id, $plugin_definition, $instance, $settings, $weight);
+
+    // Reset internal pointer since we're dealing with objects now.
+    reset($this->field['columns']);
+    $this->column = key($this->field['columns']);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(array $items, $delta, array $element, $langcode, array &$form, array &$form_state) {
+    // Prepare some properties for the child methods to build the actual form
+    // element.
+    $this->entity = $element['#entity'];
+    $this->required = $element['#required'];
+    $this->multiple = ($this->field['cardinality'] == FIELD_CARDINALITY_UNLIMITED) || ($this->field['cardinality'] > 1);
+    $this->has_value = isset($items[0][$this->column]);
+
+    // Add our custom validator.
+    $element['#element_validate'][] = array(get_class($this), 'validateElement');
+    $element['#key_column'] = $this->column;
+
+    // The rest of the $element is built by child method implementations.
+
+    return $element;
+  }
+
+  /**
+   * Form validation handler for widget elements.
+   *
+   * @param array $element
+   *   The form element.
+   * @param array $form_state
+   *   The form state.
+   */
+  public static function validateElement(array $element, array &$form_state) {
+    if ($element['#required'] && $element['#value'] == '_none') {
+      form_error($element, t('!name field is required.', array('!name' => $element['#title'])));
+    }
+
+    // Massage submitted form values.
+    // Drupal\field\Plugin\Type\Widget\WidgetBase::submit() expects values as
+    // an array of values keyed by delta first, then by column, while our
+    // widgets return the opposite.
+
+    if (is_array($element['#value'])) {
+      $values = array_values($element['#value']);
+    }
+    else {
+      $values = array($element['#value']);
+    }
+
+    // Filter out the 'none' option. Use a strict comparison, because
+    // 0 == 'any string'.
+    $index = array_search('_none', $values, TRUE);
+    if ($index !== FALSE) {
+      unset($values[$index]);
+    }
+
+    // Transpose selections from field => delta to delta => field.
+    $items = array();
+    foreach ($values as $value) {
+      $items[] = array($element['#key_column'] => $value);
+    }
+    form_set_value($element, $items, $form_state);
+  }
+
+  /**
+   * Returns the array of options for the widget.
+   *
+   * @return array
+   *   The array of options for the widget.
+   */
+  protected function getOptions() {
+    if (!isset($this->options)) {
+      // Get the list of options from the field type module, and sanitize them.
+      $options = (array) module_invoke($this->field['module'], 'options_list', $this->field, $this->instance, $this->entity);
+      array_walk_recursive($options, array($this, 'sanitizeLabel'));
+
+      // Options might be nested ("optgroups"). If the widget does not support
+      // nested options, flatten the list.
+      if (!$this->supportsGroups()) {
+        $options = $this->flattenOptions($options);
+      }
+
+      // Add an empty option if the widget needs one.
+      if ($empty_option = $this->getEmptyOption()) {
+        $label = theme('options_none', array('option' => $empty_option, 'widget' => $this, 'instance' => $this->instance));
+        $options = array('_none' => $label) + $options;
+      }
+
+      $this->options = $options;
+    }
+    return $this->options;
+  }
+
+  /**
+   * Determines selected options from the incoming field values.
+   *
+   * @param array $items
+   *   The field values.
+   *
+   * @return array
+   *   The array of corresponding selected options.
+   */
+  protected function getSelectedOptions(array $items) {
+    // We need to check against a flat list of options.
+    $flat_options = $this->flattenOptions($this->getOptions());
+
+    $selected_options = array();
+    foreach ($items as $item) {
+      $value = $item[$this->column];
+      // Keep the value if it actually is in the list of options (needs to be
+      // checked against the flat list).
+      if (isset($flat_options[$value])) {
+        $selected_options[] = $value;
+      }
+    }
+
+    return $selected_options;
+  }
+
+  /**
+   * Flattens an array of allowed values.
+   *
+   * @param array $array
+   *   A single or multidimensional array.
+   *
+   * @return array
+   *   The flattened array.
+   */
+  protected function flattenOptions(array $array) {
+    $result = array();
+    array_walk_recursive($array, function($a, $b) use (&$result) { $result[$b] = $a; });
+    return $result;
+  }
+
+  /**
+   * Indicates whether the widgets support optgroups.
+   *
+   * @return bool
+   *   TRUE if the widget supports optgroups, FALSE otherwise.
+   */
+  protected function supportsGroups() {
+    return FALSE;
+  }
+
+  /**
+   * Sanitizes a string label to display as an option.
+   *
+   * @param string $label
+   *   The label to sanitize.
+   */
+  static protected function sanitizeLabel(&$label) {
+    // Allow a limited set of HTML tags.
+    $label = field_filter_xss($label);
+  }
+
+  /**
+   * Returns the empty option to add to the list of options, if any.
+   *
+   * @return string|null
+   *   Either static::OPTIONS_EMPTY_NONE, static::OPTIONS_EMPTY_SELECT, or NULL.
+   */
+  protected function getEmptyOption() { }
+
+}
diff --git a/core/modules/options/lib/Drupal/options/Plugin/field/widget/SelectWidget.php b/core/modules/options/lib/Drupal/options/Plugin/field/widget/SelectWidget.php
new file mode 100644
index 00000000000..b17a448925c
--- /dev/null
+++ b/core/modules/options/lib/Drupal/options/Plugin/field/widget/SelectWidget.php
@@ -0,0 +1,85 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\options\Plugin\field\widget\SelectWidget.
+ */
+
+namespace Drupal\options\Plugin\field\widget;
+
+use Drupal\Component\Annotation\Plugin;
+use Drupal\Core\Annotation\Translation;
+
+/**
+ * Plugin implementation of the 'options_select' widget.
+ *
+ * @Plugin(
+ *   id = "options_select",
+ *   module = "options",
+ *   label = @Translation("Select list"),
+ *   field_types = {
+ *     "list_integer",
+ *     "list_float",
+ *     "list_text"
+ *   },
+ *   multiple_values = TRUE
+ * )
+ */
+class SelectWidget extends OptionsWidgetBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(array $items, $delta, array $element, $langcode, array &$form, array &$form_state) {
+    $element = parent::formElement($items, $delta, $element, $langcode, $form, $form_state);
+
+    $element += array(
+      '#type' => 'select',
+      '#options' => $this->getOptions(),
+      '#default_value' => $this->getSelectedOptions($items),
+      // Do not display a 'multiple' select box if there is only one option.
+      '#multiple' => $this->multiple && count($this->options) > 1,
+    );
+
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  static protected function sanitizeLabel(&$label) {
+    // Select form inputs allow unencoded HTML entities, but no HTML tags.
+    $label = strip_tags($label);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function supportsGroups() {
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEmptyOption() {
+    if ($this->multiple) {
+      // Multiple select: add a 'none' option for non-required fields.
+      if (!$this->required) {
+        return static::OPTIONS_EMPTY_NONE;
+      }
+    }
+    else {
+      // Single select: add a 'none' option for non-required fields,
+      // and a 'select a value' option for required fields that do not come
+      // with a value selected.
+      if (!$this->required) {
+        return static::OPTIONS_EMPTY_NONE;
+      }
+      if (!$this->has_value) {
+        return static::OPTIONS_EMPTY_SELECT;
+      }
+    }
+  }
+
+}
diff --git a/core/modules/options/lib/Drupal/options/Tests/OptionsWidgetsTest.php b/core/modules/options/lib/Drupal/options/Tests/OptionsWidgetsTest.php
index 023f01298cc..78efa3e320f 100644
--- a/core/modules/options/lib/Drupal/options/Tests/OptionsWidgetsTest.php
+++ b/core/modules/options/lib/Drupal/options/Tests/OptionsWidgetsTest.php
@@ -62,8 +62,7 @@ class OptionsWidgetsTest extends FieldTestBase {
       'type' => 'list_boolean',
       'cardinality' => 1,
       'settings' => array(
-        // Make sure that 0 works as a 'on' value'.
-        'allowed_values' => array(1 => 'Zero', 0 => 'Some <script>dangerous</script> & unescaped <strong>markup</strong>'),
+        'allowed_values' => array(0 => 'Zero', 1 => 'Some <script>dangerous</script> & unescaped <strong>markup</strong>'),
       ),
     );
     $this->bool = field_create_field($this->bool);
@@ -458,7 +457,7 @@ class OptionsWidgetsTest extends FieldTestBase {
     // Submit form: check the option.
     $edit = array("bool[$langcode]" => TRUE);
     $this->drupalPost(NULL, $edit, t('Save'));
-    $this->assertFieldValues($entity_init, 'bool', $langcode, array(0));
+    $this->assertFieldValues($entity_init, 'bool', $langcode, array(1));
 
     // Display form: check that the right options are selected.
     $this->drupalGet('test-entity/manage/' . $entity->ftid . '/edit');
@@ -467,7 +466,7 @@ class OptionsWidgetsTest extends FieldTestBase {
     // Submit form: uncheck the option.
     $edit = array("bool[$langcode]" => FALSE);
     $this->drupalPost(NULL, $edit, t('Save'));
-    $this->assertFieldValues($entity_init, 'bool', $langcode, array(1));
+    $this->assertFieldValues($entity_init, 'bool', $langcode, array(0));
 
     // Display form: with 'off' value, option is unchecked.
     $this->drupalGet('test-entity/manage/' . $entity->ftid . '/edit');
diff --git a/core/modules/options/options.api.php b/core/modules/options/options.api.php
index 2a303d5c7b2..e92768ff78d 100644
--- a/core/modules/options/options.api.php
+++ b/core/modules/options/options.api.php
@@ -20,8 +20,7 @@
  *   properties to filter out values from a list defined by field level
  *   properties.
  * @param \Drupal\Core\Entity\EntityInterface $entity
- *   The entity object the field is attached to, or NULL if no entity
- *   exists (e.g. in field settings page).
+ *   The entity object the field is attached to.
  *
  * @return
  *   The array of options for the field. Array keys are the values to be
diff --git a/core/modules/options/options.module b/core/modules/options/options.module
index 3789af54ffd..1062f7fc3cc 100644
--- a/core/modules/options/options.module
+++ b/core/modules/options/options.module
@@ -8,6 +8,7 @@
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\field\FieldUpdateForbiddenException;
+use Drupal\options\Plugin\field\widget\OptionsWidgetBase;
 
 /**
  * Implements hook_help().
@@ -436,400 +437,6 @@ function options_field_is_empty($item, $field) {
   return FALSE;
 }
 
-/**
- * Implements hook_field_widget_info().
- *
- * Field type modules willing to use those widgets should:
- * - Use hook_field_widget_info_alter() to append their field own types to the
- *   list of types supported by the widgets,
- * - Implement hook_options_list() to provide the list of options.
- */
-function options_field_widget_info() {
-  return array(
-    'options_select' => array(
-      'label' => t('Select list'),
-      'field types' => array('list_integer', 'list_float', 'list_text', 'entity_reference'),
-      'behaviors' => array(
-        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
-      ),
-    ),
-    'options_buttons' => array(
-      'label' => t('Check boxes/radio buttons'),
-      'field types' => array('list_integer', 'list_float', 'list_text', 'list_boolean', 'entity_reference'),
-      'behaviors' => array(
-        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
-      ),
-    ),
-    'options_onoff' => array(
-      'label' => t('Single on/off checkbox'),
-      'field types' => array('list_boolean'),
-      'behaviors' => array(
-        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
-      ),
-      'settings' => array('display_label' => 0),
-    ),
-  );
-}
-
-/**
- * Implements hook_field_widget_form().
- */
-function options_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
-  // Abstract over the actual field columns, to allow different field types to
-  // reuse those widgets.
-
-  // Reset internal pointer since we're dealing with objects now.
-  reset($field['columns']);
-  $value_key = key($field['columns']);
-
-  $type = str_replace('options_', '', $instance['widget']['type']);
-  $multiple = $field['cardinality'] > 1 || $field['cardinality'] == FIELD_CARDINALITY_UNLIMITED;
-  $required = $element['#required'];
-  $has_value = isset($items[0][$value_key]);
-  $properties = _options_properties($type, $multiple, $required, $has_value);
-
-  $entity_type = $element['#entity_type'];
-  $entity = $element['#entity'];
-
-  // Prepare the list of options.
-  $options = _options_get_options($field, $instance, $properties, $entity);
-
-  // Put current field values in shape.
-  $default_value = _options_storage_to_form($items, $options, $value_key, $properties);
-
-  switch ($type) {
-    case 'select':
-      $element += array(
-        '#type' => 'select',
-        '#default_value' => $default_value,
-        // Do not display a 'multiple' select box if there is only one option.
-        '#multiple' => $multiple && count($options) > 1,
-        '#options' => $options,
-      );
-      break;
-
-    case 'buttons':
-      // If required and there is one single option, preselect it.
-      if ($required && count($options) == 1) {
-        reset($options);
-        $default_value = array(key($options));
-      }
-
-      // If this is a single-value field, take the first default value, or
-      // default to NULL so that the form element is properly recognized as
-      // not having a default value.
-      if (!$multiple) {
-        $default_value = $default_value ? reset($default_value) : NULL;
-      }
-
-      $element += array(
-        '#type' => $multiple ? 'checkboxes' : 'radios',
-        // Radio buttons need a scalar value.
-        '#default_value' => $default_value,
-        '#options' => $options,
-      );
-      break;
-
-    case 'onoff':
-      $keys = array_keys($options);
-      $off_value = array_shift($keys);
-      $on_value = array_shift($keys);
-      $element += array(
-        '#type' => 'checkbox',
-        '#default_value' => (isset($default_value[0]) && $default_value[0] == $on_value) ? 1 : 0,
-        '#on_value' => $on_value,
-        '#off_value' => $off_value,
-      );
-      // Override the title from the incoming $element.
-      $element['#title'] = isset($options[$on_value]) ? $options[$on_value] : '';
-
-      if ($instance['widget']['settings']['display_label']) {
-        $element['#title'] = $instance['label'];
-      }
-      break;
-  }
-
-  $element += array(
-    '#value_key' => $value_key,
-    '#element_validate' => array('options_field_widget_validate'),
-    '#properties' => $properties,
-  );
-
-  return $element;
-}
-
-/**
- * Implements hook_field_widget_settings_form().
- */
-function options_field_widget_settings_form($field, $instance) {
-  $form = array();
-  if ($instance['widget']['type'] == 'options_onoff') {
-    $form['display_label'] = array(
-      '#type' => 'checkbox',
-      '#title' => t('Use field label instead of the "On value" as label'),
-      '#default_value' => $instance['widget']['settings']['display_label'],
-      '#weight' => -1,
-    );
-  }
-  return $form;
-}
-
-/**
- * Form element validation handler for options elements.
- */
-function options_field_widget_validate($element, &$form_state) {
-  if ($element['#required'] && $element['#value'] == '_none') {
-    form_error($element, t('!name field is required.', array('!name' => $element['#title'])));
-  }
-  // Transpose selections from field => delta to delta => field, turning
-  // multiple selected options into multiple parent elements.
-  $items = _options_form_to_storage($element);
-  form_set_value($element, $items, $form_state);
-}
-
-/**
- * Describes the preparation steps required by each widget.
- *
- * @param $type
- *   The type of widget: select, buttons, or onoff.
- * @param $multiple
- *   TRUE if the field allows multiple values; FALSE otherwise.
- * @param $required
- *   TRUE if a value is required for the field; FALSE otherwise.
- * @param $has_value
- *   TRUE if a value is selected.
- *
- * @return
- *   An array of properties for the widget.
- */
-function _options_properties($type, $multiple, $required, $has_value) {
-  $base = array(
-    'filter_xss' => FALSE,
-    'strip_tags' => FALSE,
-    'empty_option' => FALSE,
-    'optgroups' => FALSE,
-  );
-
-  $properties = array();
-
-  switch ($type) {
-    case 'select':
-      $properties = array(
-        // Select boxes do not support any HTML tag.
-        'strip_tags' => TRUE,
-        'optgroups' => TRUE,
-      );
-      if ($multiple) {
-        // Multiple select: add a 'none' option for non-required fields.
-        if (!$required) {
-          $properties['empty_option'] = 'option_none';
-        }
-      }
-      else {
-        // Single select: add a 'none' option for non-required fields,
-        // and a 'select a value' option for required fields that do not come
-        // with a value selected.
-        if (!$required) {
-          $properties['empty_option'] = 'option_none';
-        }
-        elseif (!$has_value) {
-          $properties['empty_option'] = 'option_select';
-        }
-      }
-      break;
-
-    case 'buttons':
-      $properties = array(
-        'filter_xss' => TRUE,
-      );
-      // Add a 'none' option for non-required radio buttons.
-      if (!$required && !$multiple) {
-        $properties['empty_option'] = 'option_none';
-      }
-      break;
-
-    case 'onoff':
-      $properties = array(
-        'filter_xss' => TRUE,
-      );
-      break;
-  }
-
-  return $properties + $base;
-}
-
-/**
- * Collects the options for a field.
- */
-function _options_get_options($field, $instance, $properties, EntityInterface $entity) {
-  // Get the list of options.
-  $options = (array) module_invoke($field['module'], 'options_list', $field, $instance, $entity);
-
-  // Sanitize the options.
-  _options_prepare_options($options, $properties);
-
-  if (!$properties['optgroups']) {
-    $options = options_array_flatten($options);
-  }
-
-  if ($properties['empty_option']) {
-    $label = theme('options_none', array('instance' => $instance, 'option' => $properties['empty_option']));
-    $options = array('_none' => $label) + $options;
-  }
-
-  return $options;
-}
-
-/**
- * Sanitizes the options recursively to support optgroups.
- *
- * @param $options
- *   The option array.
- * @param $properties
- *   An array containing the properties of the widget.
- */
-function _options_prepare_options(&$options, $properties) {
-  foreach ($options as $value => $label) {
-    // Recurse for optgroups.
-    if (is_array($label)) {
-      _options_prepare_options($options[$value], $properties);
-    }
-    else {
-      if ($properties['strip_tags']) {
-        $options[$value] = strip_tags($label);
-      }
-      if ($properties['filter_xss']) {
-        $options[$value] = field_filter_xss($label);
-      }
-    }
-  }
-}
-
-/**
- * Transforms stored field values into the format the widgets need.
- *
- * @param $items
- *   An array of stored field values.
- * @param $options
- *   The options array.
- * @param $column
- *   The field storage column of the field.
- * @param $properties
- *   An array containing the properties of the widget.
- *
- * @return
- *   An array of values in the format used by widgets.
- */
-function _options_storage_to_form($items, $options, $column, $properties) {
-  $items_transposed = options_array_transpose($items);
-  $values = (isset($items_transposed[$column]) && is_array($items_transposed[$column])) ? $items_transposed[$column] : array();
-
-  // Discard values that are not in the current list of options. Flatten the
-  // array if needed.
-  if ($properties['optgroups']) {
-    $options = options_array_flatten($options);
-  }
-  $values = array_values(array_intersect($values, array_keys($options)));
-  return $values;
-}
-
-/**
- * Transforms submitted form values into field storage format.
- *
- * @param $element
- *   The form element.
- *
- * @return
- *   An array of field values in field storage format.
- */
-function _options_form_to_storage($element) {
-  $values = array_values((array) $element['#value']);
-  $properties = $element['#properties'];
-
-  // On/off checkbox: transform '0 / 1' into the 'on / off' values.
-  if ($element['#type'] == 'checkbox') {
-    $values = array($values[0] ? $element['#on_value'] : $element['#off_value']);
-  }
-
-  // Filter out the 'none' option. Use a strict comparison, because
-  // 0 == 'any string'.
-  if ($properties['empty_option']) {
-    $index = array_search('_none', $values, TRUE);
-    if ($index !== FALSE) {
-      unset($values[$index]);
-    }
-  }
-
-  // Make sure we populate at least an empty value.
-  if (empty($values)) {
-    $values = array(NULL);
-  }
-
-  $result = options_array_transpose(array($element['#value_key'] => $values));
-  return $result;
-}
-
-/**
- * Manipulates a 2D array to reverse rows and columns.
- *
- * The default data storage for fields is delta first, column names second. This
- * is sometimes inconvenient for field modules, so this function can be used to
- * present the data in an alternate format.
- *
- * @param $array
- *   The array to be transposed. It must be at least two-dimensional, and the
- *   subarrays must all have the same keys or behavior is undefined.
- *
- * @return
- *   The transposed array.
- */
-function options_array_transpose($array) {
-  $result = array();
-  if (is_array($array)) {
-    foreach ($array as $key1 => $value1) {
-      if (is_array($value1)) {
-        foreach ($value1 as $key2 => $value2) {
-          if (!isset($result[$key2])) {
-            $result[$key2] = array();
-          }
-          $result[$key2][$key1] = $value2;
-        }
-      }
-    }
-  }
-  return $result;
-}
-
-/**
- * Flattens an array of allowed values.
- *
- * @param $array
- *   A single or multidimensional array.
- * @return
- *   A flattened array.
- */
-function options_array_flatten($array) {
-  $result = array();
-  if (is_array($array)) {
-    foreach ($array as $key => $value) {
-      if (is_array($value)) {
-        $result += options_array_flatten($value);
-      }
-      else {
-        $result[$key] = $value;
-      }
-    }
-  }
-  return $result;
-}
-
-/**
- * Implements hook_field_widget_error().
- */
-function options_field_widget_error($element, $error, $form, &$form_state) {
-  form_error($element, $error['message']);
-}
-
 /**
  * Implements hook_options_list().
  */
@@ -840,27 +447,32 @@ function options_options_list($field, $instance, $entity) {
 /**
  * Returns HTML for the label for the empty value for non-required options.
  *
- * The default theme will display N/A for a radio list and '- None -' for a
- * select.
+ * The default theme will display 'N/A' for a radio list and '- None -' or
+ * 'Select a value' for a select.
  *
  * @param $variables
  *   An associative array containing:
- *   - instance: An array representing the widget requesting the options.
+ *   - option: A string representing the option that should be displayed. Either
+ *     \Drupal\options\Plugin\field\widget\OptionsWidgetBase::OPTIONS_EMPTY_NONE
+ *     or
+ *     \Drupal\options\Plugin\field\widget\OptionsWidgetBase::OPTIONS_EMPTY_SELECT.
+ *   - widget: The widget object requesting the option.
+ *   - instance: The instance definition.
  *
  * @ingroup themeable
  */
 function theme_options_none($variables) {
-  $instance = $variables['instance'];
   $option = $variables['option'];
+  $widget = $variables['widget'];
 
   $output = '';
-  switch ($instance['widget']['type']) {
+  switch ($widget->getPluginId()) {
     case 'options_buttons':
       $output = t('N/A');
       break;
 
     case 'options_select':
-      $output = ($option == 'option_none' ? t('- None -') : t('- Select a value -'));
+      $output = ($option == OptionsWidgetBase::OPTIONS_EMPTY_NONE ? t('- None -') : t('- Select a value -'));
       break;
   }
 
diff --git a/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
index 43d2ac84381..483d0355a77 100644
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -1155,8 +1155,7 @@ function taxonomy_field_formatter_view(EntityInterface $entity, $field, $instanc
  *   properties to filter out values from a list defined by field level
  *   properties.
  * @param \Drupal\Core\Entity\EntityInterface $entity
- *   The entity object the field is attached to, or NULL if no entity
- *   exists (e.g. in field settings page).
+ *   The entity object the field is attached to.
  *
  * @return
  *   The array of valid terms for this field, keyed by term id.