Extending an existing renderer

[nvayalil]

Hi,
I read the documentation for extending ImageRenderer class, and my implementation working fine but duplicating the code. How can I call the parent ImageRenderer class inside my code instead?

class MyImageRenderer implements InlineRendererInterface, ConfigurationAwareInterface
{
    protected $config;
    public function render(AbstractInline $inline, ElementRendererInterface $htmlRenderer)
    {
        if (!($inline instanceof Image)) {
            throw new \InvalidArgumentException('Incompatible inline type: ' . \get_class($inline));
        }

        $attrs = $inline->getData('attributes', []);

        $forbidUnsafeLinks = !$this->config->get('allow_unsafe_links');
        if ($forbidUnsafeLinks && RegexHelper::isLinkPotentiallyUnsafe($inline->getUrl())) {
            $attrs['src'] = '';
        } else {
            $attrs['src'] = $inline->getUrl();
        }

        $alt = $htmlRenderer->renderInlines($inline->children());
        $alt = \preg_replace('/\<[^>]*alt="([^"]*)"[^>]*\>/', '$1', $alt);
        $attrs['alt'] = \preg_replace('/\<[^>]*\>/', '', $alt);

        if (isset($inline->data['title'])) {
            $attrs['title'] = $inline->data['title'];
        }

        return new HtmlElement('figure', [], 
                array(
                    new HtmlElement('img', $attrs, '', true),
                    new HtmlElement('figcaption', ['class' => 'font-medium'], $attrs['alt'])
                )
            );
    }

    public function setConfiguration(ConfigurationInterface $configuration)
    {
        $this->config = $configuration;
    }
}

[colinodell]

Most renderers have only one method - render(). If you were to extend a renderer (like MyImageRenderer extends ImageRenderer) you wouldn't be able to change the inside of the parent render() method. You should instead consider implementing the decorator design pattern:

final class MyImageRenderer implements InlineRendererInterface, ConfigurationAwareInterface
{
    private ImageRenderer $innerRenderer;

    public function __construct(ImageRenderer $imageRenderer)
    {
        $this->innerRenderer = $imageRenderer;
    }

    public function render(AbstractInline $inline, ElementRendererInterface $htmlRenderer)
    {
        if (!($inline instanceof Image)) {
            throw new \InvalidArgumentException('Incompatible inline type: ' . \get_class($inline));
        }

        // Have the core renderer generate the necessary `HtmlElement` or `string`
        $output = $this->innerRenderer->render($inline, $htmlRenderer);

        // TODO: Modify those $output contents here

        return $output;
    }
}

Otherwise, if you do end up copy-pasting and duplicating some code, that's probably fine too.

[nvayalil]

private ImageRenderer $innerRenderer;
Does the above work with php 7.3? I am getting error? Is there any work around for php 7.3?

[colinodell]

Ah, that only works on 7.4. Simply remove the ImageRenderer part of that line and it should work on 7.3!

[nvayalil]

I had done that but I got some other errors so I thought it may related to the declaration.

When used the class you wrote here (after removing ImageRenderer), the error was

Symfony\Component\ErrorHandler\Error\FatalError
Class App\Classes\MyImageRenderer contains 1 abstract method and must therefore be declared abstract or implement the remaining methods (League\CommonMark\Util\ConfigurationAwareInterface::setConfiguration) 

So I added

public function setConfiguration(ConfigurationInterface $configuration)
    {
        $this->config = $configuration;
    }

Now, getting the following.

ArgumentCountError
Too few arguments to function MyImageRenderer::__construct(), 0 passed in Markdown.php on line 15 and exactly 1 expected

Sorry, but I don't know how to solve this.