[FR] Add BEFORE_RENDER_ELEMENT event to ElementHelper

[leevigraham]

I would like to override the _parials template rendering logic with my own logic while retaining the developer ergonomics of .render.

Something like:

if (Event::hasHandlers(static::class, self::EVENT_BEFORE_RENDER_ELEMENT)) {
    $output = null;
    $event = new BeforeRenderElementEvent([
        'element' => $element,
        'variables' => $variables,
        'templates' => $templates,
        'output' => $output,
    ]);
    Event::trigger(static::class, self::EVENT_BEFORE_RENDER_ELEMENT, $event);
    return $event->output;
}

[brandonkelly]

I moved the rendering logic over to Element::render() and added an EVENT_RENDER event from there, for Craft 5.8: (013f83c)

use craft\base\Element;
use craft\events\RenderElementEvent;
use yii\base\Event;

Event::on(Element::class, Element::EVENT_RENDER, function(RenderElementEvent $event) {
    /** @var Element $element */
    $element = $event->sender;

    $event->output = '…';
});

[leevigraham]

@brandonkelly I've implemented this locally and it works as I hoped.

One possible improvement… Can the event fire after the template path logic and send the templates through to the event?

The only downside of this is that a developer may want to render an element that doesn't have a refHandle.

My implementation looks like this:

public function transform(Element $element): ?UxComponentInterface
    {
        $refHandle = $element::refHandle();
        if ($refHandle === null) {
            throw new NotSupportedException(sprintf('Element type “%s” doesn’t define a reference handle, so it doesn’t support ux components.', $element::displayName()));
        }

        $generalConfig = Craft::$app->getConfig()->getGeneral();
        $componentNameParts = explode(DIRECTORY_SEPARATOR, $generalConfig->partialTemplatesPath);
        $componentNameParts[] = $refHandle;

        $handle = $element->getFieldLayout()?->provider?->getHandle();
        if ($handle) {
            $componentNameParts[] = $handle;
        }

        $templatePath = implode(DIRECTORY_SEPARATOR, $componentNameParts);
        $componentNameParts[] = ucfirst(end($componentNameParts));
        $className = "templates\\".implode("\\", $componentNameParts);

        // Create a class with the block handle
        if (class_exists($className)) {
            $config = [
                '__class' => $className,
                $refHandle => $element,
                'templatePath' => $templatePath
            ];
            return Craft::createObject($config);
        }

        return null;
    }

You can see I'm repeating a lot of the same code to determine the _partial template path and then creating a PHP object to handle the rendering of each element.

[brandonkelly]

I just refactored render() a bit, and added a templates property to the event (42c1ce0).

Note that it will be set to an array of arrays with template and priority values. Element::render() will end up sorting the array on priority before looping through them.

[leevigraham]

@brandonkelly Also regarding these lines: https://github.com/craftcms/cms/blob/5.8/src/base/Element.php#L6855-L6864

I think these are redundant from my testing.

These lines: https://github.com/craftcms/cms/blob/5.8/src/base/Element.php#L6866-L6869

Seem to apply the entryType for entries to the template paths. That said I don't fully understand $entryType->original->handle

[brandonkelly]

It’s for entry types with overridden handles, via their section/Matrix field. If the overridden handle doesn’t resolve to a template, we check for a template that uses the original handle.

[leevigraham]

Ah right. I'll test that with my component renderer.