Renderer.php 16 KB
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<?php

/**
 * @file
 * Contains \Drupal\Core\Render\Renderer.
 */

namespace Drupal\Core\Render;

use Drupal\Core\Controller\ControllerResolverInterface;
use Drupal\Core\Theme\ThemeManagerInterface;
use Drupal\Component\Utility\SafeMarkup;
use Drupal\Core\Cache\Cache;
use Drupal\Component\Utility\NestedArray;

/**
 * Turns a render array into a HTML string.
 */
class Renderer implements RendererInterface {

  /**
   * The theme manager.
   *
   * @var \Drupal\Core\Theme\ThemeManagerInterface
   */
  protected $theme;

  /**
   * The controller resolver.
   *
   * @var \Drupal\Core\Controller\ControllerResolverInterface
   */
  protected $controllerResolver;

  /**
   * The element info.
   *
   * @var \Drupal\Core\Render\ElementInfoManagerInterface
   */
  protected $elementInfo;

  /**
   * Constructs a new Renderer.
   *
   * @param \Drupal\Core\Controller\ControllerResolverInterface $controller_resolver
   *   The controller resolver.
   * @param \Drupal\Core\Theme\ThemeManagerInterface $theme
   *   The theme manager.
   * @param \Drupal\Core\Render\ElementInfoManagerInterface $element_info
   *   The element info.
   */
  public function __construct(ControllerResolverInterface $controller_resolver, ThemeManagerInterface $theme, ElementInfoManagerInterface $element_info) {
    $this->controllerResolver = $controller_resolver;
    $this->theme = $theme;
    $this->elementInfo = $element_info;
  }

  /**
   * {@inheritdoc}
   */
  public function renderRoot(&$elements) {
    return $this->render($elements, TRUE);
  }

  /**
   * {@inheritdoc}
   */
  public function render(&$elements, $is_root_call = FALSE) {
    static $stack;

    $update_stack = function(&$element) use (&$stack) {
      // The latest frame represents the bubbleable data for the subtree.
      $frame = $stack->top();
      // Update the frame, but also update the current element, to ensure it
      // contains up-to-date information in case it gets render cached.
      $frame->tags = $element['#cache']['tags'] = Cache::mergeTags($element['#cache']['tags'], $frame->tags);
      $frame->attached = $element['#attached'] = drupal_merge_attached($element['#attached'], $frame->attached);
      $frame->postRenderCache = $element['#post_render_cache'] = NestedArray::mergeDeep($element['#post_render_cache'], $frame->postRenderCache);
    };

    $bubble_stack = function() use (&$stack) {
      // If there's only one frame on the stack, then this is the root call, and
      // we can't bubble up further. Reset the stack for the next root call.
      if ($stack->count() === 1) {
        $stack = NULL;
        return;
      }

      // Merge the current and the parent stack frame.
      $current = $stack->pop();
      $parent = $stack->pop();
      $current->tags = Cache::mergeTags($current->tags, $parent->tags);
      $current->attached = drupal_merge_attached($current->attached, $parent->attached);
      $current->postRenderCache = NestedArray::mergeDeep($current->postRenderCache, $parent->postRenderCache);
      $stack->push($current);
    };

    if (!isset($elements['#access']) && isset($elements['#access_callback'])) {
      if (is_string($elements['#access_callback']) && strpos($elements['#access_callback'], '::') === FALSE) {
        $elements['#access_callback'] = $this->controllerResolver->getControllerFromDefinition($elements['#access_callback']);
      }
      $elements['#access'] = call_user_func($elements['#access_callback'], $elements);
    }

    // Early-return nothing if user does not have access.
    if (empty($elements) || (isset($elements['#access']) && !$elements['#access'])) {
      return '';
    }

    // Do not print elements twice.
    if (!empty($elements['#printed'])) {
      return '';
    }

    if (!isset($stack)) {
      $stack = new \SplStack();
    }
    $stack->push(new RenderStackFrame());

    // Try to fetch the prerendered element from cache, run any
    // #post_render_cache callbacks and return the final markup.
    if (isset($elements['#cache'])) {
      $cached_element = drupal_render_cache_get($elements);
      if ($cached_element !== FALSE) {
        $elements = $cached_element;
        // Only when we're not in a root (non-recursive) drupal_render() call,
        // #post_render_cache callbacks must be executed, to prevent breaking
        // the render cache in case of nested elements with #cache set.
        if ($is_root_call) {
          $this->processPostRenderCache($elements);
        }
        $elements['#markup'] = SafeMarkup::set($elements['#markup']);
        // The render cache item contains all the bubbleable rendering metadata
        // for the subtree.
        $update_stack($elements);
        // Render cache hit, so rendering is finished, all necessary info
        // collected!
        $bubble_stack();
        return $elements['#markup'];
      }
    }

    // If the default values for this element have not been loaded yet, populate
    // them.
    if (isset($elements['#type']) && empty($elements['#defaults_loaded'])) {
      $elements += $this->elementInfo->getInfo($elements['#type']);
    }

    // Make any final changes to the element before it is rendered. This means
    // that the $element or the children can be altered or corrected before the
    // element is rendered into the final text.
    if (isset($elements['#pre_render'])) {
      foreach ($elements['#pre_render'] as $callable) {
        if (is_string($callable) && strpos($callable, '::') === FALSE) {
          $callable = $this->controllerResolver->getControllerFromDefinition($callable);
        }
        // Since #pre_render callbacks may be used for generating a render
        // array's content, and we might be rendering the main content for the
        // page, it is possible that a #pre_render callback throws an exception
        // that will cause a different page to be rendered (e.g. throwing
        // \Symfony\Component\HttpKernel\Exception\NotFoundHttpException will
        // cause the 404 page to be rendered). That page might also use
        // drupal_render(), but if exceptions aren't caught here, the stack will
        // be left in an inconsistent state.
        // Hence, catch all exceptions and reset the stack and re-throw them.
        try {
          $elements = call_user_func($callable, $elements);
        }
        catch (\Exception $e) {
          // Reset stack and re-throw exception.
          $stack = NULL;
          throw $e;
        }
      }
    }

    // Defaults for bubbleable rendering metadata.
    $elements['#cache']['tags'] = isset($elements['#cache']['tags']) ? $elements['#cache']['tags'] : array();
    $elements['#attached'] = isset($elements['#attached']) ? $elements['#attached'] : array();
    $elements['#post_render_cache'] = isset($elements['#post_render_cache']) ? $elements['#post_render_cache'] : array();

    // Allow #pre_render to abort rendering.
    if (!empty($elements['#printed'])) {
      // The #printed element contains all the bubbleable rendering metadata for
      // the subtree.
      $update_stack($elements);
      // #printed, so rendering is finished, all necessary info collected!
      $bubble_stack();
      return '';
    }

    // Add any JavaScript state information associated with the element.
    if (!empty($elements['#states'])) {
      drupal_process_states($elements);
    }

    // Get the children of the element, sorted by weight.
    $children = Element::children($elements, TRUE);

    // Initialize this element's #children, unless a #pre_render callback
    // already preset #children.
    if (!isset($elements['#children'])) {
      $elements['#children'] = '';
    }

    // @todo Simplify after https://drupal.org/node/2273925
    if (isset($elements['#markup'])) {
      $elements['#markup'] = SafeMarkup::set($elements['#markup']);
    }

    // Assume that if #theme is set it represents an implemented hook.
    $theme_is_implemented = isset($elements['#theme']);
    // Check the elements for insecure HTML and pass through sanitization.
    if (isset($elements)) {
      $markup_keys = array(
        '#description',
        '#field_prefix',
        '#field_suffix',
      );
      foreach ($markup_keys as $key) {
        if (!empty($elements[$key]) && is_scalar($elements[$key])) {
          $elements[$key] = SafeMarkup::checkAdminXss($elements[$key]);
        }
      }
    }

    // Call the element's #theme function if it is set. Then any children of the
    // element have to be rendered there. If the internal #render_children
    // property is set, do not call the #theme function to prevent infinite
    // recursion.
    if ($theme_is_implemented && !isset($elements['#render_children'])) {
      $elements['#children'] = $this->theme->render($elements['#theme'], $elements);

      // If ThemeManagerInterface::render() returns FALSE this means that the
      // hook in #theme was not found in the registry and so we need to update
      // our flag accordingly. This is common for theme suggestions.
      $theme_is_implemented = ($elements['#children'] !== FALSE);
    }

    // If #theme is not implemented or #render_children is set and the element
    // has an empty #children attribute, render the children now. This is the
    // same process as Renderer::render() but is inlined for speed.
    if ((!$theme_is_implemented || isset($elements['#render_children'])) && empty($elements['#children'])) {
      foreach ($children as $key) {
        $elements['#children'] .= $this->render($elements[$key]);
      }
      $elements['#children'] = SafeMarkup::set($elements['#children']);
    }

    // If #theme is not implemented and the element has raw #markup as a
    // fallback, prepend the content in #markup to #children. In this case
    // #children will contain whatever is provided by #pre_render prepended to
    // what is rendered recursively above. If #theme is implemented then it is
    // the responsibility of that theme implementation to render #markup if
    // required. Eventually #theme_wrappers will expect both #markup and
    // #children to be a single string as #children.
    if (!$theme_is_implemented && isset($elements['#markup'])) {
      $elements['#children'] = SafeMarkup::set($elements['#markup'] . $elements['#children']);
    }

    // Let the theme functions in #theme_wrappers add markup around the rendered
    // children.
    // #states and #attached have to be processed before #theme_wrappers,
    // because the #type 'page' render array from drupal_prepare_page() would
    // render the $page and wrap it into the html.html.twig template without the
    // attached assets otherwise.
    // If the internal #render_children property is set, do not call the
    // #theme_wrappers function(s) to prevent infinite recursion.
    if (isset($elements['#theme_wrappers']) && !isset($elements['#render_children'])) {
      foreach ($elements['#theme_wrappers'] as $key => $value) {
        // If the value of a #theme_wrappers item is an array then the theme
        // hook is found in the key of the item and the value contains attribute
        // overrides. Attribute overrides replace key/value pairs in $elements
        // for only this ThemeManagerInterface::render() call. This allows
        // #theme hooks and #theme_wrappers hooks to share variable names
        // without conflict or ambiguity.
        $wrapper_elements = $elements;
        if (is_string($key)) {
          $wrapper_hook = $key;
          foreach ($value as $attribute => $override) {
            $wrapper_elements[$attribute] = $override;
          }
        }
        else {
          $wrapper_hook = $value;
        }

        $elements['#children'] = $this->theme->render($wrapper_hook, $wrapper_elements);
      }
    }

    // Filter the outputted content and make any last changes before the content
    // is sent to the browser. The changes are made on $content which allows the
    // outputted text to be filtered.
    if (isset($elements['#post_render'])) {
      foreach ($elements['#post_render'] as $callable) {
        if (is_string($callable) && strpos($callable, '::') === FALSE) {
          $callable = $this->controllerResolver->getControllerFromDefinition($callable);
        }
        $elements['#children'] = call_user_func($callable, $elements['#children'], $elements);
      }
    }

    // We store the resulting output in $elements['#markup'], to be consistent
    // with how render cached output gets stored. This ensures that
    // #post_render_cache callbacks get the same data to work with, no matter if
    // #cache is disabled, #cache is enabled, there is a cache hit or miss.
    $prefix = isset($elements['#prefix']) ? SafeMarkup::checkAdminXss($elements['#prefix']) : '';
    $suffix = isset($elements['#suffix']) ? SafeMarkup::checkAdminXss($elements['#suffix']) : '';

    $elements['#markup'] = $prefix . $elements['#children'] . $suffix;

    // We've rendered this element (and its subtree!), now update the stack.
    $update_stack($elements);

    // Cache the processed element if #cache is set.
    if (isset($elements['#cache'])) {
      drupal_render_cache_set($elements['#markup'], $elements);
    }

    // Only when we're in a root (non-recursive) drupal_render() call,
    // #post_render_cache callbacks must be executed, to prevent breaking the
    // render cache in case of nested elements with #cache set.
    //
    // By running them here, we ensure that:
    // - they run when #cache is disabled,
    // - they run when #cache is enabled and there is a cache miss.
    // Only the case of a cache hit when #cache is enabled, is not handled here,
    // that is handled earlier in Renderer::render().
    if ($is_root_call) {
      // We've already called $update_stack() earlier, which updated both the
      // element and current stack frame. However,
      // Renderer::processPostRenderCache() can both change the element
      // further and create and render new child elements, so provide a fresh
      // stack frame to collect those additions, merge them back to the element,
      // and then update the current frame to match the modified element state.
      $stack->push(new RenderStackFrame());
      $this->processPostRenderCache($elements);
      $post_render_additions = $stack->pop();
      $elements['#cache']['tags'] = Cache::mergeTags($elements['#cache']['tags'], $post_render_additions->tags);
      $elements['#attached'] = drupal_merge_attached($elements['#attached'], $post_render_additions->attached);
      $elements['#post_render_cache'] = NestedArray::mergeDeep($elements['#post_render_cache'], $post_render_additions->postRenderCache);
      if ($stack->count() !== 1) {
        throw new \LogicException('A stray drupal_render() invocation with $is_root_call = TRUE is causing bubbling of attached assets to break.');
      }
    }

    // Rendering is finished, all necessary info collected!
    $bubble_stack();

    $elements['#printed'] = TRUE;
    $elements['#markup'] = SafeMarkup::set($elements['#markup']);
    return $elements['#markup'];
  }

  /**
   * Processes #post_render_cache callbacks.
   *
   * #post_render_cache callbacks may modify:
   * - #markup: to replace placeholders
   * - #attached: to add libraries or JavaScript settings
   *
   * Note that in either of these cases, #post_render_cache callbacks are
   * implicitly idempotent: a placeholder that has been replaced can't be
   * replaced again, and duplicate attachments are ignored.
   *
   * @param array &$elements
   *   The structured array describing the data being rendered.
   *
   * @see drupal_render_collect_post_render_cache
   */
  protected function processPostRenderCache(array &$elements) {
    if (isset($elements['#post_render_cache'])) {

      // Call all #post_render_cache callbacks, passing the provided context.
      foreach (array_keys($elements['#post_render_cache']) as $callback) {
        if (strpos($callback, '::') === FALSE) {
          $callable = $this->controllerResolver->getControllerFromDefinition($callback);
        }
        else {
          $callable = $callback;
        }
        foreach ($elements['#post_render_cache'][$callback] as $context) {
          $elements = call_user_func_array($callable, array($elements, $context));
        }
      }
    }
  }

}