Issue #2940201 by xjm, amateescu, benjifisher, tedbow, tim.plunkett, Berdir:...

Issue #2940201 by xjm, amateescu, benjifisher, tedbow, tim.plunkett, Berdir: hook_field_widget_form_alter() can no longer affect the whole widget for multi-value fields

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

@@ -241,6 +241,19 @@ protected function formMultipleElements(FieldItemListInterface $items, array &$f
           ],
         ];
       }
+
+      // Allow modules to alter the field multi-value widget form element.
+      // This hook can also be used for single-value fields.
+      $context = [
+        'form' => $form,
+        'widget' => $this,
+        'items' => $items,
+        'default' => $this->isDefaultValueWidget($form_state),
+      ];
+      \Drupal::moduleHandler()->alter([
+        'field_widget_multivalue_form',
+        'field_widget_multivalue_' . $this->getPluginId() . '_form',
+      ], $elements, $form_state, $context);
     }
 
     return $elements;

core/modules/field/field.api.php

@@ -164,6 +164,11 @@ function hook_field_widget_info_alter(array &$info) {
 /**
  * Alter forms for field widgets provided by other modules.
  *
+ * This hook can only modify individual elements within a field widget and
+ * cannot alter the top level (parent element) for multi-value fields. In most
+ * cases, you should use hook_field_widget_multivalue_form_alter() instead and
+ * loop over the elements.
+ *
  * @param $element
  *   The field widget form element as constructed by
  *   \Drupal\Core\Field\WidgetBaseInterface::form().
@@ -183,6 +188,7 @@ function hook_field_widget_info_alter(array &$info) {
  * @see \Drupal\Core\Field\WidgetBaseInterface::form()
  * @see \Drupal\Core\Field\WidgetBase::formSingleElement()
  * @see hook_field_widget_WIDGET_TYPE_form_alter()
+ * @see hook_field_widget_multivalue_form_alter()
  */
 function hook_field_widget_form_alter(&$element, \Drupal\Core\Form\FormStateInterface $form_state, $context) {
   // Add a css class to widget form elements for all fields of type mytype.
@@ -200,6 +206,11 @@ function hook_field_widget_form_alter(&$element, \Drupal\Core\Form\FormStateInte
  * specific widget form, rather than using hook_field_widget_form_alter() and
  * checking the widget type.
  *
+ * This hook can only modify individual elements within a field widget and
+ * cannot alter the top level (parent element) for multi-value fields. In most
+ * cases, you should use hook_field_widget_multivalue_WIDGET_TYPE_form_alter()
+ * instead and loop over the elements.
+ *
  * @param $element
  *   The field widget form element as constructed by
  *   \Drupal\Core\Field\WidgetBaseInterface::form().
@@ -212,6 +223,7 @@ function hook_field_widget_form_alter(&$element, \Drupal\Core\Form\FormStateInte
  * @see \Drupal\Core\Field\WidgetBaseInterface::form()
  * @see \Drupal\Core\Field\WidgetBase::formSingleElement()
  * @see hook_field_widget_form_alter()
+ * @see hook_field_widget_multivalue_WIDGET_TYPE_form_alter()
  */
 function hook_field_widget_WIDGET_TYPE_form_alter(&$element, \Drupal\Core\Form\FormStateInterface $form_state, $context) {
   // Code here will only act on widgets of type WIDGET_TYPE.  For example,
@@ -220,6 +232,74 @@ function hook_field_widget_WIDGET_TYPE_form_alter(&$element, \Drupal\Core\Form\F
   $element['#autocomplete_route_name'] = 'mymodule.autocomplete_route';
 }
 
+/**
+ * Alter forms for multi-value field widgets provided by other modules.
+ *
+ * To alter the individual elements within the widget, loop over
+ * \Drupal\Core\Render\Element::children($elements).
+ *
+ * @param array $elements
+ *   The field widget form elements as constructed by
+ *   \Drupal\Core\Field\WidgetBase::formMultipleElements().
+ * @param \Drupal\Core\Form\FormStateInterface $form_state
+ *   The current state of the form.
+ * @param array $context
+ *   An associative array containing the following key-value pairs:
+ *   - form: The form structure to which widgets are being attached. This may be
+ *     a full form structure, or a sub-element of a larger form.
+ *   - widget: The widget plugin instance.
+ *   - items: The field values, as a
+ *     \Drupal\Core\Field\FieldItemListInterface object.
+ *   - default: A boolean indicating whether the form is being shown as a dummy
+ *     form to set default values.
+ *
+ * @see \Drupal\Core\Field\WidgetBaseInterface::form()
+ * @see \Drupal\Core\Field\WidgetBase::formMultipleElements()
+ * @see hook_field_widget_multivalue_WIDGET_TYPE_form_alter()
+ */
+function hook_field_widget_multivalue_form_alter(array &$elements, \Drupal\Core\Form\FormStateInterface $form_state, array $context) {
+  // Add a css class to widget form elements for all fields of type mytype.
+  $field_definition = $context['items']->getFieldDefinition();
+  if ($field_definition->getType() == 'mytype') {
+    // Be sure not to overwrite existing attributes.
+    $elements['#attributes']['class'][] = 'myclass';
+  }
+}
+
+/**
+ * Alter multi-value widget forms for a widget provided by another module.
+ *
+ * Modules can implement hook_field_widget_multivalue_WIDGET_TYPE_form_alter() to
+ * modify a specific widget form, rather than using
+ * hook_field_widget_form_alter() and checking the widget type.
+ *
+ * To alter the individual elements within the widget, loop over
+ * \Drupal\Core\Render\Element::children($elements).
+ *
+ * @param array $elements
+ *   The field widget form elements as constructed by
+ *   \Drupal\Core\Field\WidgetBase::formMultipleElements().
+ * @param \Drupal\Core\Form\FormStateInterface $form_state
+ *   The current state of the form.
+ * @param array $context
+ *   An associative array. See hook_field_widget_multivalue_form_alter() for
+ *   the structure and content of the array.
+ *
+ * @see \Drupal\Core\Field\WidgetBaseInterface::form()
+ * @see \Drupal\Core\Field\WidgetBase::formMultipleElements()
+ * @see hook_field_widget_multivalue_form_alter()
+ */
+function hook_field_widget_multivalue_WIDGET_TYPE_form_alter(array &$elements, \Drupal\Core\Form\FormStateInterface $form_state, array $context) {
+  // Code here will only act on widgets of type WIDGET_TYPE. For example,
+  // hook_field_widget_multivalue_mymodule_autocomplete_form_alter() will only
+  // act on widgets of type 'mymodule_autocomplete'.
+  // Change the autcomplete route for each autocomplete element within the
+  // multivalue widget.
+  foreach (Element::children($elements) as $delta => $element) {
+    $elements[$delta]['#autocomplete_route_name'] = 'mymodule.autocomplete_route';
+  }
+}
+
 /**
  * @} End of "defgroup field_widget".
  */

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

@@ -113,6 +113,9 @@ public function testFieldFormSingle() {
     // Check that hook_field_widget_form_alter() does not believe this is the
     // default value form.
     $this->assertNoText('From hook_field_widget_form_alter(): Default form is true.', 'Not default value form in hook_field_widget_form_alter().');
+    // Check that hook_field_widget_form_alter() does not believe this is the
+    // default value form.
+    $this->assertNoText('From hook_field_widget_multivalue_form_alter(): Default form is true.', 'Not default value form in hook_field_widget_form_alter().');
 
     // Submit with invalid value (field-level validation).
     $edit = [
@@ -634,4 +637,44 @@ public function testLabelOnMultiValueFields() {
     $this->assertEscaped("<script>alert('a configurable field');</script>");
   }
 
+  /**
+   * Tests hook_field_widget_multivalue_form_alter().
+   */
+  public function testFieldFormMultipleWidgetAlter() {
+    $this->widgetAlterTest('hook_field_widget_multivalue_form_alter');
+  }
+
+  /**
+   * Tests hook_field_widget_multivalue_WIDGET_TYPE_form_alter().
+   */
+  public function testFieldFormMultipleWidgetTypeAlter() {
+    $this->widgetAlterTest('hook_field_widget_multivalue_WIDGET_TYPE_form_alter');
+  }
+
+  /**
+   * Tests widget alter hooks for a given hook name.
+   */
+  protected function widgetAlterTest($hook) {
+    // Set a flag in state so that the hook implementations will run.
+    \Drupal::state()->set("field_test.$hook", TRUE);
+
+    // Create a field with fixed cardinality, configure the form to use a
+    // "multiple" widget.
+    $field_storage = $this->fieldStorageMultiple;
+    $field_name = $field_storage['field_name'];
+    $this->field['field_name'] = $field_name;
+    FieldStorageConfig::create($field_storage)->save();
+    FieldConfig::create($this->field)->save();
+    entity_get_form_display($this->field['entity_type'], $this->field['bundle'], 'default')
+      ->setComponent($field_name, [
+        'type' => 'test_field_widget_multiple',
+      ])
+      ->save();
+
+    $this->drupalGet('entity_test/add');
+    $this->assertUniqueText("From $hook(): prefix on field_test_text parent element.");
+    $this->assertText("From $hook(): description on field_test_text child element.");
+    $this->drupalGet('entity_test/add');
+  }
+
 }

core/modules/field/tests/modules/field_test/field_test.module

@@ -15,6 +15,7 @@
 
 use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Render\Element;
 use Drupal\field\FieldStorageConfigInterface;
 
 require_once __DIR__ . '/field_test.entity.inc';
@@ -100,16 +101,6 @@ function field_test_entity_display_build_alter(&$output, $context) {
  * Implements hook_field_widget_form_alter().
  */
 function field_test_field_widget_form_alter(&$element, FormStateInterface $form_state, $context) {
-  $field_definition = $context['items']->getFieldDefinition();
-  switch ($field_definition->getName()) {
-    case 'alter_test_text':
-      drupal_set_message('Field size: ' . $context['widget']->getSetting('size'));
-      break;
-
-    case 'alter_test_options':
-      drupal_set_message('Widget type: ' . $context['widget']->getPluginId());
-      break;
-  }
   // Set a message if this is for the form displayed to set default value for
   // the field.
   if ($context['default']) {
@@ -117,6 +108,43 @@ function field_test_field_widget_form_alter(&$element, FormStateInterface $form_
   }
 }
 
+/**
+ * Implements hook_field_widget_multivalue_form_alter().
+ */
+function field_test_field_widget_multivalue_form_alter(array &$elements, FormStateInterface $form_state, array $context) {
+  _field_test_alter_widget("hook_field_widget_multivalue_form_alter", $elements, $form_state, $context);
+}
+
+/**
+ * Implements hook_field_widget_multivalue_form_alter().
+ */
+function field_test_field_widget_multivalue_text_textfield_form_alter(array &$elements, FormStateInterface $form_state, array $context) {
+  _field_test_alter_widget("hook_field_widget_multivalue_WIDGET_TYPE_form_alter", $elements, $form_state, $context);
+}
+
+/**
+ * Sets up alterations for widget alter tests.
+ *
+ * @see \Drupal\field\Tests\FormTest::widgetAlterTest()
+ */
+function _field_test_alter_widget($hook, array &$elements, FormStateInterface $form_state, array $context) {
+
+  // Set a message if this is for the form displayed to set default value for
+  // the field.
+  if ($context['default']) {
+    drupal_set_message("From $hook(): Default form is true.");
+  }
+  if (\Drupal::state()->get("field_test.$hook")) {
+    $name = $context['items']->getFieldDefinition()->getName();
+    if ($name === 'field_test_text') {
+      $elements['#prefix'] = "From $hook(): prefix on $name parent element.";
+      foreach (Element::children($elements) as $delta => $element) {
+        $elements[$delta]['#description'] = "From $hook(): description on $name child element.";
+      }
+    }
+  }
+}
+
 /**
  * Implements hook_query_TAG_alter() for tag 'efq_table_prefixing_test'.
  *