diff --git a/core/lib/Drupal/Core/Entity/ContentEntityFormController.php b/core/lib/Drupal/Core/Entity/ContentEntityFormController.php
index d0383d6..b258508 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityFormController.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityFormController.php
@@ -149,7 +149,7 @@ public function buildEntity(array $form, array &$form_state) {
     $entity = clone $this->entity;
 
     // First, extract values from widgets.
-    $extracted = $this->EntityFormHelper->extractWidgetsValue($entity, $form_state['form_display'], $form, $form_state);
+    $extracted = $this->EntityFormHelper->extractWidgetsValues($entity, $form_state['form_display'], $form, $form_state);
 
     // Then extract the values of fields that are not rendered through widgets,
     // by simply copying from top-level form values. This leaves the fields
diff --git a/core/lib/Drupal/Core/Entity/ContentEntityFormHelper.php b/core/lib/Drupal/Core/Entity/ContentEntityFormHelper.php
index de0b5e1..6cc8c5c 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityFormHelper.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityFormHelper.php
@@ -1,4 +1,5 @@
 <?php
+
 /**
  * @file
  * Contains \Drupal\Core\Entity\ContentEntityFormHelper
@@ -17,12 +18,91 @@ class ContentEntityFormHelper {
   /**
    * Adds field widgets to the form.
    *
+   * The form elements for the entity's fields are added by reference as direct
+   * children in the $form parameter. This parameter can be a full form
+   * structure (most common case for entity edit forms), or a sub-element of a
+   * larger form.
+   *
+   * By default, submitted field values appear at the top-level of
+   * $form_state['values']. A different location within $form_state['values']
+   * can be specified by setting the '#parents' property on the incoming $form
+   * parameter. Because of name clashes, two instances of the same field cannot
+   * appear within the same $form element, or within the same '#parents' space.
+   *
+   * Sample resulting structure in $form:
+   * @code
+   *   '#parents' => The location of field values in $form_state['values'],
+   *   '#entity_type' => The name of the entity type,
+   *   '#bundle' => The name of the bundle,
+   *   // One sub-array per field appearing in the entity, keyed by field name.
+   *   // The structure of the array differs slightly depending on whether the
+   *   // widget is 'single-value' (provides the input for one field value,
+   *   // most common case), and will therefore be repeated as many times as
+   *   // needed, or 'multiple-values' (one single widget allows the input of
+   *   // several values, e.g checkboxes, select box...).
+   *   'field_foo' => array(
+   *     '#access' => TRUE if the current user has 'edit' grants for the field,
+   *       FALSE if not.
+   *     'widget' => array(
+   *       '#field_name' => The name of the field,
+   *       '#language' => $langcode,
+   *       '#field_parents' => The 'parents' space for the field in the form,
+   *          equal to the #parents property of the $form parameter received by
+   *          field_attach_form(),
+   *       '#required' => Whether or not the field is required,
+   *       '#title' => The label of the field instance,
+   *       '#description' => The description text for the field instance,
+   *
+   *       // Only for 'single' widgets:
+   *       '#theme' => 'field_multiple_value_form',
+   *       '#cardinality' => The field cardinality,
+   *       '#cardinality_multiple => TRUE if the field can contain multiple
+   *         items, FALSE otherwise.
+   *       // One sub-array per copy of the widget, keyed by delta.
+   *       0 => array(
+   *         '#entity_type' => The name of the entity type,
+   *         '#bundle' => The name of the bundle,
+   *         '#field_name' => The name of the field,
+   *         '#field_parents' => The 'parents' space for the field in the form,
+   *            equal to the #parents property of the $form parameter,
+   *         '#title' => The title to be displayed by the widget,
+   *         '#default_value' => The field value for delta 0,
+   *         '#required' => Whether the widget should be marked required,
+   *         '#delta' => 0,
+   *         // The remaining elements in the sub-array depend on the widget.
+   *         '#type' => The type of the widget,
+   *         ...
+   *       ),
+   *       1 => array(
+   *         ...
+   *       ),
+   *
+   *       // Only for multiple widgets:
+   *       '#entity_type' => The name of the entity type,
+   *       '#bundle' => $instance['bundle'],
+   *       // The remaining elements in the sub-array depend on the widget.
+   *       '#type' => The type of the widget,
+   *       ...
+   *     ),
+   *     ...
+   *   ),
+   * )
+   * @endcode
+   *
+   * Additionally, some processing data is placed in $form_state, and can be
+   * accessed by field_form_get_state() and field_form_set_state().
+   *
    * @param EntityInterface $entity
    *   The entity.
    * @param EntityFormDisplayInterface $display
    *   The form display containing the widget settings.
    * @param array $form
-   *   The form.
+   *   The form structure to fill in. This can be a full form structure, or a
+   *   sub-element of a larger form. The #parents property can be set to
+   *   control the location of submitted field values within
+   *   $form_state['values']. If not specified, $form['#parents'] is set to an
+   *   empty array, which results in field values located at the top-level of
+   *   $form_state['values'].
    * @param array $form_state
    *   The form state.
    */
@@ -47,18 +127,22 @@ public function attachWidgets(EntityInterface $entity, EntityFormDisplayInterfac
     // @todo hook_field_attach_form() ?
     // We still need a hook to allow alteration of "forms with widgets", because
     // the regular "entity form" alter hook won't run non "non enity forms"...
-    // Although,  there's already hook_field_widget_form_alter() to alter each widget ?
+    // Although, there's already hook_field_widget_form_alter() to alter each widget ?
   }
 
   /**
    * Extracts field values from the submitted widget values into the entity.
    *
+   * This accounts for drag-and-drop reordering of field values, and filtering
+   * of empty values.
+   *
    * @param EntityInterface $entity
    *   The entity.
    * @param EntityFormDisplayInterface $display
    *   The form display containing the widget settings.
    * @param array $form
-   *   The form.
+   *   The form structure where field elements are attached to. This might be a
+   *   full form structure, or a sub-element of a larger form.
    * @param array $form_state
    *   The form state.
    *
@@ -68,7 +152,7 @@ public function attachWidgets(EntityInterface $entity, EntityFormDisplayInterfac
    *   any, do not correspond to widgets and should be extracted manually by
    *   the caller if needed.
    */
-  public function extractWidgetsValue(EntityInterface $entity, EntityFormDisplayInterface $display, array &$form, array &$form_state) {
+  public function extractWidgetsValues(EntityInterface $entity, EntityFormDisplayInterface $display, array &$form, array &$form_state) {
     $extracted = array();
 
     foreach ($entity as $name => $items) {
@@ -85,12 +169,29 @@ public function extractWidgetsValue(EntityInterface $entity, EntityFormDisplayIn
   /**
    * Validates submitted widget values and sets the corresponding form errors.
    *
+   * There are two levels of validation for fields in forms: widget validation
+   * and field validation.
+   * - Widget validation steps are specific to a given widget's own form
+   *   structure and UI metaphors. They are executed during normal form
+   *   validation, usually through Form API's #element_validate property.
+   *   Errors reported at this level are typically those that prevent the
+   *   extraction of proper field values from the submitted form input.
+   * - If no form / widget errors were reported for the field, field validation
+   *   steps are performed according to the "constraints" specified by the
+   *   field definition. Those are independent of the specific widget being
+   *   used in a given form, and are also performed on REST entity submissions.
+   *
+   * This function performs field validation in the context of a form submission.
+   * It reports field constraint violations as form errors on the correct form
+   * elements.
+   *
    * @param EntityInterface $entity
    *   The entity.
    * @param EntityFormDisplayInterface $display
    *   The form display containing the widget settings.
    * @param array $form
-   *   The form.
+   *   The form structure where field elements are attached to. This might be a
+   *   full form structure, or a sub-element of a larger form.
    * @param array $form_state
    *   The form state.
    */
diff --git a/core/modules/edit/lib/Drupal/edit/Form/EditFieldForm.php b/core/modules/edit/lib/Drupal/edit/Form/EditFieldForm.php
index 7ae8698..944da20 100644
--- a/core/modules/edit/lib/Drupal/edit/Form/EditFieldForm.php
+++ b/core/modules/edit/lib/Drupal/edit/Form/EditFieldForm.php
@@ -58,6 +58,8 @@ class EditFieldForm extends FormBase {
    *   The module handler.
    * @param \Drupal\Core\Entity\EntityStorageControllerInterface $node_type_storage
    *   The node type storage.
+   * @param \Drupal\Core\Entity\ContentEntityFormHelper $entity_form_helper
+   *   The ContentEntity form helper.
    */
   public function __construct(TempStoreFactory $temp_store_factory, ModuleHandlerInterface $module_handler, EntityStorageControllerInterface $node_type_storage, ContentEntityFormHelper $entity_form_helper) {
     $this->tempStoreFactory = $temp_store_factory;
@@ -189,7 +191,7 @@ protected function buildEntity(array $form, array &$form_state) {
     $entity = clone $form_state['entity'];
     $field_name = $form_state['field_name'];
 
-    $this->entityFormHelper->extractWidgetsValue($entity, $form_state['form_display'], $form, $form_state);
+    $this->entityFormHelper->extractWidgetsValues($entity, $form_state['form_display'], $form, $form_state);
 
     // @todo Refine automated log messages and abstract them to all entity
     //   types: http://drupal.org/node/1678002.
diff --git a/core/modules/field/field.api.php b/core/modules/field/field.api.php
index 8341c7a..807fe56 100644
--- a/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -11,15 +11,16 @@
 /**
  * Exposes "pseudo-field" components on fieldable entities.
  *
- * Field UI's "Manage fields" and "Manage display" pages let users re-order
- * fields, but also non-field components. For nodes, these include the title
- * and other elements exposed by modules through hook_form_alter().
+ * Field UI's "Manage display" and "Manage form display" pages let users
+ * re-order fields rendered through the regular widget/formatter pipeline, but
+ * also other components: entity fields that are rendered through custom code,
+ * or other arbitrary components added through hook_form_alter() or
+ * hook_entity_view().
  *
  * Fieldable entities or modules that want to have their components supported
  * should expose them using this hook. The user-defined settings (weight,
  * visible) are automatically applied on rendered forms and displayed entities
- * in a #pre_render callback added by field_attach_form() and
- * field_attach_view().
+ * by ContentEntityFormController::form() and EntityViewBuilder::viewMultiple().
  *
  * @see hook_field_extra_fields_alter()
  *
@@ -162,8 +163,8 @@ function hook_field_info_alter(&$info) {
  *
  * Widgets are @link forms_api_reference.html Form API @endlink
  * elements with additional processing capabilities. The methods of the
- * WidgetInterface object are typically called by the Field Attach API during
- * the creation of the field form structure with field_attach_form().
+ * WidgetInterface object are typically called by respective methods in the
+ * ContentEntityFormHelper class.
  *
  * @see field
  * @see field_types
diff --git a/core/modules/field/field.deprecated.inc b/core/modules/field/field.deprecated.inc
index 1358149..25b9c5e 100644
--- a/core/modules/field/field.deprecated.inc
+++ b/core/modules/field/field.deprecated.inc
@@ -438,83 +438,6 @@ function field_read_instances($conditions = array(), $include_additional = array
 /**
  * Adds form elements for all fields for an entity to a form structure.
  *
- * The form elements for the entity's fields are added by reference as direct
- * children in the $form parameter. This parameter can be a full form structure
- * (most common case for entity edit forms), or a sub-element of a larger form.
- *
- * By default, submitted field values appear at the top-level of
- * $form_state['values']. A different location within $form_state['values'] can
- * be specified by setting the '#parents' property on the incoming $form
- * parameter. Because of name clashes, two instances of the same field cannot
- * appear within the same $form element, or within the same '#parents' space.
- *
- * For each call to field_attach_form(), field values are processed by calling
- * field_attach_extract_form_values() on the same $form element.
- *
- * Sample resulting structure in $form:
- * @code
- *   '#parents' => The location of field values in $form_state['values'],
- *   '#entity_type' => The name of the entity type,
- *   '#bundle' => The name of the bundle,
- *   // One sub-array per field appearing in the entity, keyed by field name.
- *   // The structure of the array differs slightly depending on whether the
- *   // widget is 'single-value' (provides the input for one field value,
- *   // most common case), and will therefore be repeated as many times as
- *   // needed, or 'multiple-values' (one single widget allows the input of
- *   // several values, e.g checkboxes, select box...).
- *   'field_foo' => array(
- *     '#access' => TRUE if the current user has 'edit' grants for the field,
- *       FALSE if not.
- *     'widget' => array(
- *       '#field_name' => The name of the field,
- *       '#language' => $langcode,
- *       '#field_parents' => The 'parents' space for the field in the form,
- *          equal to the #parents property of the $form parameter received by
- *          field_attach_form(),
- *       '#required' => Whether or not the field is required,
- *       '#title' => The label of the field instance,
- *       '#description' => The description text for the field instance,
- *
- *       // Only for 'single' widgets:
- *       '#theme' => 'field_multiple_value_form',
- *       '#cardinality' => The field cardinality,
- *       '#cardinality_multiple => TRUE if the field can contain multiple items,
- *         FALSE otherwise.
- *       // One sub-array per copy of the widget, keyed by delta.
- *       0 => array(
- *         '#entity_type' => The name of the entity type,
- *         '#bundle' => The name of the bundle,
- *         '#field_name' => The name of the field,
- *         '#field_parents' => The 'parents' space for the field in the form,
- *            equal to the #parents property of the $form parameter received by
- *            field_attach_form(),
- *         '#title' => The title to be displayed by the widget,
- *         '#default_value' => The field value for delta 0,
- *         '#required' => Whether the widget should be marked required,
- *         '#delta' => 0,
- *         // The remaining elements in the sub-array depend on the widget.
- *         '#type' => The type of the widget,
- *         ...
- *       ),
- *       1 => array(
- *         ...
- *       ),
- *
- *       // Only for multiple widgets:
- *       '#entity_type' => The name of the entity type,
- *       '#bundle' => $instance['bundle'],
- *       // The remaining elements in the sub-array depend on the widget.
- *       '#type' => The type of the widget,
- *       ...
- *     ),
- *     ...
- *   ),
- * )
- * @endcode
- *
- * Additionally, some processing data is placed in $form_state, and can be
- * accessed by field_form_get_state() and field_form_set_state().
- *
  * @param \Drupal\Core\Entity\EntityInterface $entity
  *   The entity for which to load form elements, used to initialize
  *   default form values.
@@ -545,20 +468,6 @@ function field_attach_form(EntityInterface $entity, &$form, &$form_state, $langc
 /**
  * Performs field validation against form-submitted field values.
  *
- * There are two levels of validation for fields in forms: widget validation and
- * and field validation.
- * - Widget validation steps are specific to a given widget's own form structure
- *   and UI metaphors. They are executed through FAPI's #element_validate
- *   property during normal form validation.
- * - Field validation steps are common to a given field type, independently of
- *   the specific widget being used in a given form. They are defined in the
- *   field type's implementation of hook_field_validate().
- *
- * This function performs field validation in the context of a form submission.
- * It converts field validation errors into form errors on the correct form
- * elements. Fieldable entity types should call this function during their own
- * form validation function.
- *
  * @param \Drupal\Core\Entity\ContentEntityInterface $entity
  *   The entity being submitted. The actual field values will be read
  *   from $form_state['values'].
@@ -580,9 +489,6 @@ function field_attach_form_validate(ContentEntityInterface $entity, $form, &$for
 /**
  * Populates an entity object with values from a form submission.
  *
- * Currently, this accounts for drag-and-drop reordering of field values, and
- * filtering of empty values.
- *
  * @param \Drupal\Core\Entity\EntityInterface $entity
  *   The entity being submitted. The actual field values will be read
  *   from $form_state['values'].
@@ -598,7 +504,7 @@ function field_attach_form_validate(ContentEntityInterface $entity, $form, &$for
  * @deprecated as of Drupal 8.0. Use the entity system instead.
  */
 function field_attach_extract_form_values(EntityInterface $entity, $form, &$form_state, array $options = array()) {
-  \Drupal::service('entity.content.form_helper')->extractWidgetsValue($entity, $form_state['form_display'], $form, $form_state);
+  \Drupal::service('entity.content.form_helper')->extractWidgetsValues($entity, $form_state['form_display'], $form, $form_state);
 }
 
 /**
diff --git a/core/modules/field/field.multilingual.inc b/core/modules/field/field.multilingual.inc
index d5d058a..60fccbc 100644
--- a/core/modules/field/field.multilingual.inc
+++ b/core/modules/field/field.multilingual.inc
@@ -36,33 +36,10 @@
  * languages, unless it is given a language code suggestion. Based on that
  * suggestion, _field_language_suggestion() determines the languages to act on.
  *
- * Most field_attach_*() functions act on all available language codes, except
- * for the following:
- * - field_attach_form() only takes a single language code, specifying which
- *   language the field values will be submitted in.
- * - field_attach_view() requires the language the entity will be displayed in.
- *   Since it is unknown whether a field translation exists for the requested
- *   language, the translation handler is responsible for performing one of the
- *   following actions:
- *   - Ignore missing translations, i.e. do not show any field values for the
- *     requested language. For example, see field_field_language_alter().
- *   - Provide a value in a different language as fallback. By default, the
- *     fallback logic is applied separately to each field to ensure that there
- *     is a value for each field to display.
- *   The field language fallback logic relies on the global language fallback
- *   configuration. Therefore, the displayed field values can be in the
- *   requested language, but may be different if no values for the requested
- *   language are available. The default language fallback rules inspect all the
- *   enabled languages ordered by their weight. This behavior can be altered or
- *   even disabled by modules implementing hook_field_language_alter(), making
- *   it possible to choose the first approach. The display language for each
- *   field is returned by field_language().
- *
  * See @link field Field API @endlink for information about the other parts of
  * the Field API.
  */
 
-
 /**
  * Collects the available language codes for the given entity type and field.
  *
diff --git a/core/modules/field/lib/Drupal/field/Tests/FieldAttachOtherTest.php b/core/modules/field/lib/Drupal/field/Tests/FieldAttachOtherTest.php
index e73b9db..690fbe3 100644
--- a/core/modules/field/lib/Drupal/field/Tests/FieldAttachOtherTest.php
+++ b/core/modules/field/lib/Drupal/field/Tests/FieldAttachOtherTest.php
@@ -318,22 +318,24 @@ function testFieldAttachCache() {
   }
 
   /**
-   * Test field_attach_form().
+   * Test \Drupal\Core\Entity\ContentEntityFormHelper::attachWidgets().
    *
    * This could be much more thorough, but it does verify that the correct
    * widgets show up.
    */
-  function testFieldAttachForm() {
+  function testFieldAttachWidgets() {
+    $entity_form_helper = \Drupal::service('entity.content.form_helper');
+
     $this->createFieldWithInstance('_2');
 
     $entity_type = 'entity_test';
     $entity = entity_create($entity_type, array('id' => 1, 'revision_id' => 1, 'type' => $this->instance->bundle));
 
-    // When generating form for all fields.
+    // Test generating widgets for all fields.
+    $display = entity_get_form_display($entity_type, $this->instance->bundle, 'default');
     $form = array();
     $form_state = form_state_defaults();
-    $form_state['form_display'] = entity_get_form_display($entity_type, $this->instance->bundle, 'default');
-    field_attach_form($entity, $form, $form_state);
+    $entity_form_helper->attachWidgets($entity, $display, $form, $form_state);
 
     $this->assertEqual($form[$this->field_name]['widget']['#title'], $this->instance->getLabel(), "First field's form title is {$this->instance->getLabel()}");
     $this->assertEqual($form[$this->field_name_2]['widget']['#title'], $this->instance_2->getLabel(), "Second field's form title is {$this->instance_2->getLabel()}");
@@ -346,7 +348,7 @@ function testFieldAttachForm() {
       $this->assertEqual($form[$this->field_name_2]['widget'][$delta]['value']['#type'], 'textfield', "Second field's form delta $delta widget is textfield");
     }
 
-    // When generating form for a single field (the second field).
+    // Test generating widgets for all fields.
     $display = entity_get_form_display($entity_type, $this->instance->bundle, 'default');
     foreach ($display->getComponents() as $name => $options) {
       if ($name != $this->field_name_2) {
@@ -355,8 +357,7 @@ function testFieldAttachForm() {
     }
     $form = array();
     $form_state = form_state_defaults();
-    $form_state['form_display'] = $display;
-    field_attach_form($entity, $form, $form_state, NULL, $options);
+    $entity_form_helper->attachWidgets($entity, $display, $form, $form_state);
 
     $this->assertFalse(isset($form[$this->field_name]), 'The first field does not exist in the form');
     $this->assertEqual($form[$this->field_name_2]['widget']['#title'], $this->instance_2->getLabel(), "Second field's form title is {$this->instance_2->getLabel()}");
@@ -367,19 +368,21 @@ function testFieldAttachForm() {
   }
 
   /**
-   * Test field_attach_extract_form_values().
+   * Test \Drupal\Core\Entity\ContentEntityFormHelper::extractWidgetsValues().
    */
   function testFieldAttachExtractFormValues() {
+    $entity_form_helper = \Drupal::service('entity.content.form_helper');
+
     $this->createFieldWithInstance('_2');
 
     $entity_type = 'entity_test';
     $entity_init = entity_create($entity_type, array('id' => 1, 'revision_id' => 1, 'type' => $this->instance->bundle));
 
     // Build the form for all fields.
+    $display = entity_get_form_display($entity_type, $this->instance->bundle, 'default');
     $form = array();
     $form_state = form_state_defaults();
-    $form_state['form_display'] = entity_get_form_display($entity_type, $this->instance->bundle, 'default');
-    field_attach_form($entity_init, $form, $form_state);
+    $entity_form_helper->attachWidgets($entity_init, $display, $form, $form_state);
 
     // Simulate incoming values.
     // First field.
@@ -417,9 +420,9 @@ function testFieldAttachExtractFormValues() {
     $form_state['values'][$this->field_name] = $values;
     $form_state['values'][$this->field_name_2] = $values_2;
 
-    // Call field_attach_extract_form_values() for all fields.
+    // Extract values for all fields.
     $entity = clone($entity_init);
-    field_attach_extract_form_values($entity, $form, $form_state);
+    $entity_form_helper->extractWidgetsValues($entity, $display, $form, $form_state);
 
     asort($weights);
     asort($weights_2);
@@ -439,20 +442,20 @@ function testFieldAttachExtractFormValues() {
     $this->assertIdentical($entity->{$this->field_name_2}->getValue(), $expected_values_2, 'Submit filters empty values');
 
     // Call field_attach_extract_form_values() for a single field (the second field).
-    foreach ($form_state['form_display']->getComponents() as $name => $options) {
+    foreach ($display->getComponents() as $name => $options) {
       if ($name != $this->field_name_2) {
-        $form_state['form_display']->removeComponent($name);
+        $display->removeComponent($name);
       }
     }
     $entity = clone($entity_init);
-    field_attach_extract_form_values($entity, $form, $form_state, $options);
+    $entity_form_helper->extractWidgetsValues($entity, $display, $form, $form_state);
     $expected_values_2 = array();
     foreach ($weights_2 as $key => $value) {
       if ($key != 1) {
         $expected_values_2[] = array('value' => $values_2[$key]['value']);
       }
     }
-    $this->assertTrue($entity->{$this->field_name}->isEmpty(), 'The first field does is empty in the entity object');
+    $this->assertTrue($entity->{$this->field_name}->isEmpty(), 'The first field is empty in the entity object');
     $this->assertIdentical($entity->{$this->field_name_2}->getValue(), $expected_values_2, 'Submit filters empty values');
   }
 
diff --git a/core/modules/field/lib/Drupal/field/Tests/FormTest.php b/core/modules/field/lib/Drupal/field/Tests/FormTest.php
index 81ec2ff..9c0e384 100644
--- a/core/modules/field/lib/Drupal/field/Tests/FormTest.php
+++ b/core/modules/field/lib/Drupal/field/Tests/FormTest.php
@@ -531,10 +531,10 @@ function testFieldFormAccess() {
     // apart from #access.
     $entity = entity_create($entity_type, array('id' => 0, 'revision_id' => 0));
 
+    $display = entity_get_form_display($entity_type, $entity_type, 'default');
     $form = array();
     $form_state = form_state_defaults();
-    $form_state['form_display'] = entity_get_form_display($entity_type, $entity_type, 'default');
-    field_attach_form($entity, $form, $form_state);
+    \Drupal::service('entity.content.form_helper')->attachWidgets($entity, $display, $form, $form_state);
 
     $this->assertEqual($form[$field_name_no_access]['widget'][0]['value']['#entity_type'], $entity_type, 'The correct entity type is set in the field structure.');
     $this->assertFalse($form[$field_name_no_access]['#access'], 'Field #access is FALSE for the field without edit access.');
diff --git a/core/modules/field/tests/modules/field_test/field_test.entity.inc b/core/modules/field/tests/modules/field_test/field_test.entity.inc
index 880636e..e562648 100644
--- a/core/modules/field/tests/modules/field_test/field_test.entity.inc
+++ b/core/modules/field/tests/modules/field_test/field_test.entity.inc
@@ -37,85 +37,3 @@ function field_test_entity_info_translatable($entity_type = NULL, $translatable
   }
   return $stored_value;
 }
-
-/**
- * Form combining two separate entities.
- *
- * @deprecated Use \Drupal\field_test\Form\FieldTestForm::testEntityNestedForm()
- */
-function field_test_entity_nested_form($form, &$form_state, $entity_1, $entity_2) {
-  // First entity.
-  foreach (array('id', 'type') as $key) {
-    $form[$key] = array(
-      '#type' => 'value',
-      '#value' => $entity_1->$key->value,
-    );
-  }
-  $form_state['form_display'] = entity_get_form_display($entity_1->entityType(), $entity_1->bundle(), 'default');
-  field_attach_form($entity_1, $form, $form_state);
-
-  // Second entity.
-  $form['entity_2'] = array(
-    '#type' => 'details',
-    '#title' => t('Second entity'),
-    '#tree' => TRUE,
-    '#parents' => array('entity_2'),
-    '#weight' => 50,
-  );
-  foreach (array('id', 'type') as $key) {
-    $form['entity_2'][$key] = array(
-      '#type' => 'value',
-      '#value' => $entity_2->$key->value,
-    );
-  }
-  $form_state['form_display'] = entity_get_form_display($entity_1->entityType(), $entity_1->bundle(), 'default');
-  field_attach_form($entity_2, $form['entity_2'], $form_state);
-
-  $form['save'] = array(
-    '#type' => 'submit',
-    '#value' => t('Save'),
-    '#weight' => 100,
-  );
-
-  return $form;
-}
-
-/**
- * Validate handler for field_test_entity_nested_form().
- */
-function field_test_entity_nested_form_validate($form, &$form_state) {
-  $entity_1 = entity_create('entity_test', array(
-    'id' => $form_state['values']['id'],
-    'type' => $form_state['values']['type'],
-  ));
-  field_attach_extract_form_values($entity_1, $form, $form_state);
-  field_attach_form_validate($entity_1, $form, $form_state);
-
-  $entity_2 = entity_create('entity_test', array(
-    'id' => $form_state['values']['entity_2']['id'],
-    'type' => $form_state['values']['entity_2']['type'],
-  ));
-  field_attach_extract_form_values($entity_2, $form['entity_2'], $form_state);
-  field_attach_form_validate($entity_2, $form['entity_2'], $form_state);
-}
-
-/**
- * Submit handler for field_test_entity_nested_form().
- */
-function field_test_entity_nested_form_submit($form, &$form_state) {
-  $entity_1 = entity_create('entity_test', array(
-    'id' => $form_state['values']['id'],
-    'type' => $form_state['values']['type'],
-  ));
-  field_attach_extract_form_values($entity_1, $form, $form_state);
-  $entity_1->save();
-
-  $entity_2 = entity_create('entity_test', array(
-    'id' => $form_state['values']['entity_2']['id'],
-    'type' => $form_state['values']['entity_2']['type'],
-  ));
-  field_attach_extract_form_values($entity_2, $form['entity_2'], $form_state);
-  $entity_2->save();
-
-  drupal_set_message(t('test_entities @id_1 and @id_2 have been updated.', array('@id_1' => $entity_1->id(), '@id_2' => $entity_2->id())));
-}
diff --git a/core/modules/field/tests/modules/field_test/field_test.routing.yml b/core/modules/field/tests/modules/field_test/field_test.routing.yml
index b7ba00c..cfd60fa 100644
--- a/core/modules/field/tests/modules/field_test/field_test.routing.yml
+++ b/core/modules/field/tests/modules/field_test/field_test.routing.yml
@@ -2,7 +2,7 @@ field_test.entity_nested_form:
   path: '/test-entity/nested/{entity_1}/{entity_2}'
   defaults:
     _title: 'Nested entity form'
-    _content: '\Drupal\field_test\Form\FieldTestForm::testEntityNestedForm'
+    _form: '\Drupal\field_test\Form\NestedEntityTestForm'
   options:
     parameters:
       entity_1:
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Form/FieldTestForm.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Form/FieldTestForm.php
deleted file mode 100644
index 8c9e913..0000000
--- a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Form/FieldTestForm.php
+++ /dev/null
@@ -1,25 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\field_test\Form\FieldTestForm.
- */
-
-namespace Drupal\field_test\Form;
-
-use Drupal\Core\Entity\EntityInterface;
-
-/**
- * Provides a form for field_test routes.
- */
-class FieldTestForm {
-
-  /**
-   * @todo Remove field_test_entity_nested_form().
-   */
-  public function testEntityNestedForm(EntityInterface $entity_1, EntityInterface $entity_2) {
-    module_load_include('entity.inc', 'field_test');
-    return drupal_get_form('field_test_entity_nested_form', $entity_1, $entity_2);
-  }
-
-}
diff --git a/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Form/NestedEntityTestForm.php b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Form/NestedEntityTestForm.php
new file mode 100644
index 0000000..9f57d96
--- /dev/null
+++ b/core/modules/field/tests/modules/field_test/lib/Drupal/field_test/Form/NestedEntityTestForm.php
@@ -0,0 +1,101 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\field_test\Form\NestedEntityTestForm.
+ */
+
+namespace Drupal\field_test\Form;
+
+use Drupal\Core\Entity\ContentEntityFormHelper;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Form\FormBase;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides a form for field_test routes.
+ */
+class NestedEntityTestForm extends FormBase {
+
+  /**
+   * The ContentEntity form helper.
+   *
+   * @var \Drupal\Core\Entity\ContentEntityFormHelper
+   */
+  protected $entityFormHelper;
+
+  public function __construct(ContentEntityFormHelper $entity_form_helper) {
+    $this->entityFormHelper = $entity_form_helper;
+  }
+
+  /**
+   * {@inheritdoc]
+   */
+  public static function create(ContainerInterface $container) {
+    return new static($container->get('entity.content.form_helper'));
+  }
+
+  /**
+   * {@inheritdoc]
+   */
+  public function getFormId() {
+    return 'field_test_entity_nested_form';
+  }
+
+  /**
+   * {@inheritdoc]
+   */
+  public function buildForm(array $form, array &$form_state, EntityInterface $entity_1 = NULL, EntityInterface $entity_2 = NULL) {
+    // First entity.
+    $form_state['entity_1'] = $entity_1;
+    $form_state['form_display_1'] = entity_get_render_form_display($entity_1, 'default');
+    $this->entityFormHelper->attachWidgets($entity_1, $form_state['form_display_1'], $form, $form_state);
+
+    // Second entity.
+    $form_state['entity_2'] = $entity_2;
+    $form_state['form_display_2'] = entity_get_render_form_display($entity_2, 'default');
+    $form['entity_2'] = array(
+      '#type' => 'details',
+      '#title' => t('Second entity'),
+      '#tree' => TRUE,
+      '#parents' => array('entity_2'),
+      '#weight' => 50,
+    );
+    $this->entityFormHelper->attachWidgets($entity_2, $form_state['form_display_2'], $form['entity_2'], $form_state);
+
+    $form['save'] = array(
+      '#type' => 'submit',
+      '#value' => t('Save'),
+      '#weight' => 100,
+    );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc]
+   */
+  public function validateForm(array &$form, array &$form_state) {
+    $entity_1 = $form_state['entity_1'];
+    $this->entityFormHelper->extractWidgetsValues($entity_1, $form_state['form_display_1'], $form, $form_state);
+    $this->entityFormHelper->validateWidgetsValues($entity_1, $form_state['form_display_1'], $form, $form_state);
+
+    $entity_2 = $form_state['entity_2'];
+    $this->entityFormHelper->extractWidgetsValues($entity_2, $form_state['form_display_2'], $form['entity_2'], $form_state);
+    $this->entityFormHelper->validateWidgetsValues($entity_2, $form_state['form_display_2'], $form['entity_2'], $form_state);
+  }
+
+  /**
+   * {@inheritdoc]
+   */
+  public function submitForm(array &$form, array &$form_state) {
+    $entity_1 = $form_state['entity_1'];
+    $entity_1->save();
+
+    $entity_2 = $form_state['entity_2'];
+    $entity_2->save();
+
+    drupal_set_message($this->t('test_entities @id_1 and @id_2 have been updated.', array('@id_1' => $entity_1->id(), '@id_2' => $entity_2->id())));
+  }
+
+}
diff --git a/core/modules/node/node.api.php b/core/modules/node/node.api.php
index 9194d3f..cde8286 100644
--- a/core/modules/node/node.api.php
+++ b/core/modules/node/node.api.php
@@ -32,13 +32,12 @@
  * - Entity hooks: Generic hooks for "entity" operations. These are always
  *   invoked on all modules.
  *
- * Here is a list of the node and entity hooks that are invoked, field
- * operations, and other steps that take place during node operations:
+ * Here is a list of the node and entity hooks that are invoked, and other
+ * steps that take place during node operations:
  * - Instantiating a new node:
  *   - hook_node_create() (all)
  *   - hook_entity_create() (all)
  * - Creating a new node (calling $node->save() on a new node):
- *   - field_attach_presave()
  *   - hook_node_presave() (all)
  *   - hook_entity_presave() (all)
  *   - Node and revision records are written to the database
@@ -47,7 +46,6 @@
  *   - hook_node_access_records() (all)
  *   - hook_node_access_records_alter() (all)
  * - Updating an existing node (calling $node->save() on an existing node):
- *   - field_attach_presave()
  *   - hook_node_presave() (all)
  *   - hook_entity_presave() (all)
  *   - Node and revision records are written to the database
@@ -94,7 +92,6 @@
  *   existing node, it will already be loaded; see the Loading section above):
  *   - hook_node_prepare_form() (all)
  *   - hook_entity_prepare_form() (all)
- *   - field_attach_form()
  * - Validating a node during editing form submit (calling
  *   node_form_validate()):
  *   - hook_node_validate() (all)
diff --git a/core/modules/system/tests/modules/form_test/form_test.module b/core/modules/system/tests/modules/form_test/form_test.module
index a932868..54281d2 100644
--- a/core/modules/system/tests/modules/form_test/form_test.module
+++ b/core/modules/system/tests/modules/form_test/form_test.module
@@ -1972,13 +1972,6 @@ function form_test_form_user_register_form_alter(&$form, &$form_state) {
     '#value' => t('Rebuild'),
     '#submit' => array('form_test_user_register_form_rebuild'),
   );
-  // If requested, add the test field by attaching the node page form.
-  if (\Drupal::request()->request->has('field')) {
-    $node = entity_create('node', array(
-      'type' => 'page',
-    ));
-    field_attach_form($node, $form, $form_state);
-  }
 }
 
 /**