core-bundle/src/Fragment/FragmentHandler.php
public function render($uri, $renderer = 'inline', array $options = []): ?string
    {
        if (!$uri instanceof FragmentReference) {
            return $this->fragmentHandler->render($uri, $renderer, $options);
        }

        $config = $this->fragmentRegistry->get($uri->controller);

        if (null === $config) {
            throw new UnknownFragmentException(sprintf('Invalid fragment identifier "%s"', $uri->controller));
        }

        $this->preHandleFragment($uri, $config);

        $renderer = $config->getRenderer();

        if (!isset($this->initialized[$renderer]) && $this->renderers->has($renderer)) {
            $this->addRenderer($this->renderers->get($renderer));
            $this->initialized[$renderer] = true;
        }

        return parent::render($uri, $renderer, $config->getOptions());
    }
public function render($uri, $renderer = 'inline', array $options = []): ?string
    {
        if (!$uri instanceof FragmentReference) {
            return $this->fragmentHandler->render($uri, $renderer, $options);
        }

        $config = $this->fragmentRegistry->get($uri->controller);

        if (null === $config) {
            throw new UnknownFragmentException(sprintf('Invalid fragment identifier "%s"', $uri->controller));
        }

        $this->preHandleFragment($uri, $config);

        $renderer = $config->getRenderer();

        if (!isset($this->initialized[$renderer]) && $this->renderers->has($renderer)) {
            $this->addRenderer($this->renderers->get($renderer));
            $this->initialized[$renderer] = true;
        }

        return parent::render($uri, $renderer, $config->getOptions());
    }
{@inheritdoc}