Update to drupal-org-drupal 8.0.0-rc2. For more information, see https://www.drupal.org/node/2598668

core/lib/Drupal/Core/Render/Element/Button.php

@@ -16,6 +16,23 @@ use Drupal\Core\Render\Element;
  * When the button is pressed, the form will be submitted to Drupal, where it is
  * validated and rebuilt. The submit handler is not invoked.
  *
+ * Properties:
+ * - #limit_validation_errors: An array of form element keys that will block
+ *   form submission when validation for these elements or any child elements
+ *   fails. Specify an empty array to suppress all form validation errors.
+ * - #value: The text to be shown on the button.
+ *
+ *
+ * Usage Example:
+ * @code
+ * $form['actions']['preview'] = array(
+ *   '#type' => 'button',
+ *   '#value => $this->t('Preview'),
+ * );
+ * @endcode
+ *
+ * @see \Drupal\Core\Render\Element\Submit
+ *
  * @FormElement("button")
  */
 class Button extends FormElement {

core/lib/Drupal/Core/Render/Element/Details.php

@@ -13,7 +13,7 @@ use Drupal\Core\Render\Element;
  * Provides a render element for a details element, similar to a fieldset.
  *
  * Fieldsets can only be used in forms, while details elements can be used
- * outside of forms.  Users click on the the title to open or close the details
+ * outside of forms. Users click on the title to open or close the details
  * element, showing or hiding the contained elements.
  *
  * Properties:

core/lib/Drupal/Core/Render/Element/Dropbutton.php

@@ -10,6 +10,36 @@ namespace Drupal\Core\Render\Element;
 /**
  * Provides a render element for a set of links rendered as a drop-down button.
  *
+ * By default, this element sets #theme so that the 'links' theme hook is used
+ * for rendering, with suffixes so that themes can override this specifically
+ * without overriding all links theming. If the #subtype property is provided in
+ * your render array with value 'foo', #theme is set to links__dropbutton__foo;
+ * if not, it's links__dropbutton; both of these can be overridden by setting
+ * the #theme property in your render array. See template_preprocess_links()
+ * for documentation on the other properties used in theming; for instance, use
+ * element property #links to provide $variables['links'] for theming.
+ *
+ * Properties:
+ * - #links: An array of links to actions. See template_preprocess_links() for
+ *   documentation the properties of links in this array.
+ *
+ * Usage Example:
+ * @code
+ * $form['actions']['extra_actions'] = array(
+ *   '#type' => 'dropbutton',
+ *   '#links' => array(
+ *     'simple_form' => array(
+ *       'title' => $this->t('Simple Form'),
+ *       'url' => Url::fromRoute('fapi_example.simple_form'),
+ *     ),
+ *     'demo' => array(
+ *       'title' => $this->t('Build Demo'),
+ *       'url' => Url::fromRoute('fapi_example.build_demo'),
+ *     ),
+ *   ),
+ * );
+ * @endcode
+ *
  * @see \Drupal\Core\Render\Element\Operations
  *
  * @RenderElement("dropbutton")

core/lib/Drupal/Core/Render/Element/Hidden.php

@@ -12,6 +12,19 @@ use Drupal\Core\Render\Element;
 /**
  * Provides a form element for an HTML 'hidden' input element.
  *
+ * Specify either #default_value or #value but not both.
+ *
+ * Properties:
+ * - #default_value: The initial value of the form element. JavaScript may
+ *   alter the value prior to submission.
+ * - #value: The value of the form element. The Form API ensures that this
+ *   value remains unchanged by the browser.
+ *
+ * Usage example:
+ * @code
+ * $form['entity_id'] = array('#type' => 'hidden', '#value' => $entity_id);
+ * @endcode
+ *
  * @see \Drupal\Core\Render\Element\Value
  *
  * @FormElement("hidden")

core/lib/Drupal/Core/Render/Element/Link.php

@@ -9,7 +9,6 @@ namespace Drupal\Core\Render\Element;
 
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\Html as HtmlUtility;
-use Drupal\Core\Cache\CacheableMetadata;
 use Drupal\Core\Render\BubbleableMetadata;
 use Drupal\Core\Url as CoreUrl;
 

core/lib/Drupal/Core/Render/Element/Operations.php

@@ -14,6 +14,8 @@ namespace Drupal\Core\Render\Element;
  * difference is that it offers themes the possibility to render it differently
  * through a theme suggestion.
  *
+ * @see \Drupal|Core\Render\Element\DropButton
+ *
  * @RenderElement("operations")
  */
 class Operations extends Dropbutton {

core/lib/Drupal/Core/Render/Element/Submit.php

@@ -13,6 +13,22 @@ namespace Drupal\Core\Render\Element;
  * Submit buttons are processed the same as regular buttons, except they trigger
  * the form's submit handler.
  *
+ * Properties:
+ * - #submit: Specifies an alternate callback for form submission when the
+ *   submit button is pressed.  Use '::methodName' format or an array containing
+ *   the object and method name (for example, [ $this, 'methodName'] ).
+ * - #value: The text to be shown on the button.
+ *
+ * Usage Example:
+ * @code
+ * $form['actions']['submit'] = array(
+ *   '#type' => 'submit,
+ *   '#value' => $this->t('Save'),
+ * );
+ * @endcode
+ *
+ * @see \Drupal\Core\Render\Element\Button
+ *
  * @FormElement("submit")
  */
 class Submit extends Button {

core/lib/Drupal/Core/Render/Element/Value.php

@@ -10,9 +10,17 @@ namespace Drupal\Core\Render\Element;
 /**
  * Provides a form element for storage of internal information.
  *
- * Unlike \Drupal\Core\Render\Element\Hidden, this information is not
- * sent to the browser in a hidden form field, but is just stored in the form
- * array for use in validation and submit processing.
+ * Unlike \Drupal\Core\Render\Element\Hidden, this information is not sent to
+ * the browser in a hidden form field, but only stored in the form array for use
+ * in validation and submit processing.
+ *
+ * Properties:
+ * - #value: The value of the form element that cannot be edited by the user.
+ *
+ * Usage Example:
+ * @code
+ * $form['entity_id'] = array('#type' => 'value', '#value' => $entity_id);
+ * @endcode
  *
  * @FormElement("value")
  */

core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php

@@ -12,9 +12,7 @@ use Drupal\Core\Asset\AttachedAssets;
 use Drupal\Core\Config\ConfigFactoryInterface;
 use Drupal\Core\Form\EnforcedResponseException;
 use Drupal\Core\Extension\ModuleHandlerInterface;
-use Drupal\Core\Render\BubbleableMetadata;
 use Drupal\Component\Utility\Html;
-use Drupal\Component\Utility\SafeMarkup;
 use Symfony\Component\HttpFoundation\RequestStack;
 
 /**

core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php

@@ -13,7 +13,6 @@ use Drupal\Core\Controller\TitleResolverInterface;
 use Drupal\Core\Display\PageVariantInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Display\ContextAwareVariantInterface;
-use Drupal\Core\Render\BubbleableMetadata;
 use Drupal\Core\Render\HtmlResponse;
 use Drupal\Core\Render\PageDisplayVariantSelectionEvent;
 use Drupal\Core\Render\RenderCacheInterface;

core/lib/Drupal/Core/Render/MainContent/ModalRenderer.php

@@ -9,7 +9,6 @@ namespace Drupal\Core\Render\MainContent;
 
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\OpenModalDialogCommand;
-use Drupal\Core\Render\MainContent\DialogRenderer;
 use Drupal\Core\Routing\RouteMatchInterface;
 use Symfony\Component\HttpFoundation\Request;