function Renderer::doRenderRoot

See the docs for ::render().

File

core/lib/Drupal/Core/Render/Renderer.php, line 236

Class

Renderer

Turns a render array into an HTML string.

Namespace

Code

protected function doRenderRoot(array &$elements, RenderContext $context) : string|MarkupInterface {
  if (!$elements) {
    return '';
  }
  // Set the bubbleable rendering metadata that has configurable defaults
  // to ensure that the final render array definitely has these configurable
  // defaults, even when no subtree is render cached.
  $required_cache_contexts = $this->rendererConfig['required_cache_contexts'];
  if (isset($elements['#cache']['contexts'])) {
    $elements['#cache']['contexts'] = Cache::mergeContexts($elements['#cache']['contexts'], $required_cache_contexts);
  }
  else {
    $elements['#cache']['contexts'] = $required_cache_contexts;
  }
  // Render the elements normally.
  $return = $this->doRender($elements, $context);
  // If there is no output, return early as placeholders can't make a
  // difference.
  if ((string) $return === '') {
    return $return;
  }
  // Only when rendering the root do placeholders have to be processed. If we
  // were to replace them while rendering cacheable nested elements, their
  // cacheable metadata would still bubble all the way up the render tree,
  // effectively making the use of placeholders pointless.
  $this->replacePlaceholders($elements);
  return $elements['#markup'];
}