No renderer found for node type: League\Commonmark + Drupal

Question

I'm trying to render markdown using League\Commonmark 2.3.8 and the extension in Drupal, when I try to render using the extension I get the following error:

Cannot find the renderer corresponding to the node type League\CommonMark\Node\Block\Document

This is my code:

class FilterMarkdown extends FilterBase {

  /**
   * @var array The private config array.
   *
   * https://commonmark.thephpleague.com/2.3/configuration/.
   */
  private array $config = [
    // Allow because only the admin has markdown access.
    'html_input' => 'allow',
    'allow_unsafe_links' => false,
  ];

  /**
   * {@inheritdoc}
   */
  public function process($text, $langcode): FilterProcessResult {
    $converter = new MarkdownConverter($this->createEnvironment());

    $converted_text = $converter->convert($text);

    return new FilterProcessResult("$converted_text");
  }

  /**
   * Generate an environment with all the extensions we need.
   */
  private function createEnvironment(): Environment {
    $environment = new Environment($this->config);
    $environment->addExtension(new ExternalLinkExtension());
    $environment->addExtension(new HeadingPermalinkExtension());
    $environment->addExtension(new StrikethroughExtension());
    $environment->addExtension(new TableExtension());

    return $environment;
  }

}

The problem is related to the way I create the environment. I know this because I overridden process() as follows, and the markdown conversion works as expected:

public function process($text, $langcode): FilterProcessResult {
    $converter = new CommonMarkConverter($this->config);

    $converted_text = $converter->convert($text);

    return new FilterProcessResult("$converted_text");
  }

I also removed all addExtension lines and got the same error, so the problem is new Environment($this->config).

Then I tried initializing without configuration: new Environment([]), but I still got the same error.

So what did I do wrong?

(Drupal has a markdown module, but I can't use it because I'm migrating the site to Drupal 10 and the module is not compatible.)

Answer 1

You will also need to add CommonMarkCoreExtension or InlinesOnlyExtension as they provide parsers and renderers for Document, etc > Paragraph and Text nodes. (Alternatively, if you need more control over which grammars are included or excluded, you can manually register individual parsers and renderers yourself).