Creating a field plug-in, need the com_content form to be enctype multipart

Question

I've been writing a field plug-in for adding files to articles in com_content. I've got the basics of the field plug-in working ok, extending the JFormFieldFile class

The issue I've hit is, for the com_content form to be able to handle the upload of the file, it needs to have the encoding type of multipart, like enctype="multipart/form-data"

I could create a template override, with the edit.php file, and change the form tag there, but I'd like the form plug-in to not be dependent on a specific template.

Does anyone know a nice way of changing the form's tag from a field plug-in?

This is the first field plug-in I've written, so am still getting the hang of it.

I've using Joomla 4.0.5, incase that's useful to know.

Answer 1

There really isn't a good way to do this. Your best bet is parsing the already generated HTML and making a replacement there. For the component this can be done using onAfterDispatch event. Below is a basic example that adds enctype attribute to all component forms with item-form ID. Regex can probably be optimized and maybe a check should be added to prevent double attribute, in case it's already added in the layout. Also note that the ID may differ in different components and views. For instance, in frontend article form it's adminForm.

public function onAfterDispatch()
{
    // Get the document.
    $doc = $this->app->getDocument();

    // Check that we are manipulating a HTML document.
    if (!($doc instanceof Joomla\CMS\Document\HtmlDocument))
    {
        return;
    }

    // Get the HTML content.
    $html = $doc->getBuffer('component');

    // Add the attribute.
    $html = preg_replace('/<form((?=[^>]*id="item-form")[^>]*)>/', '<form$1 enctype="multipart/form-data">', $html);

    // Set the updated HTML.
    $doc->setBuffer($html, 'component');
}

Depending on whether you want this to run in other components, you may add some context checks. E.g. to run this only in com_content article forms, add this at the top:

// Check that we're in correct application.
if (!$this->app->isClient('site') && !$this->app->isClient('administrator'))
{
    return;
}

$input = $this->app->getInput();

// Check the component.
if ($input->get('option') !== 'com_content')
{
    return;
}

// Check the views.
if ($this->app->isClient('site') && $input->get('view') !== 'form')
{
    return;
}

if ($this->app->isClient('administrator') && $input->get('view') !== 'article')
{
    return;
}