Registering EasyPost library in J4 module - Class not found

Question

I have created a very basic module to display EasyPost Tracking information for our customers. The module works in J3, but in J4 I get an error.

This is the code I have:

use Joomla\CMS\Factory;
$input = Factory::getApplication()->input;
$tracking_number = $input->get("tracking_number", "", "ALNUM");
$carrier = $input->get("carrier", "", "ALNUM");
$api_key = $params->get('api_key');

// add EasyPost NameSpace library
JLoader::registerNamespace('EasyPost', JPATH_LIBRARIES. '/lib');
// get EasyPost library
require_once(JPATH_LIBRARIES . '/lib/EasyPost/EasyPost.php');
// set api key
\EasyPost\EasyPost::setApiKey($api_key);

if(!empty($tracking_number)) {
    try {
        $EZtracker = \EasyPost\Tracker::create(array(
            "tracking_code" => $tracking_number,
            "carrier" => $carrier
        ));

When I call the class to set the api key it seems to work.

\EasyPost\EasyPost::setApiKey($api_key);

But when I call the static create method from tracker class with:

$EZtracker = \EasyPost\Tracker::create(array(...));

I get the error:

Message: Class "EasyPost\Tracker" not found.

How do I update this code to work in Joomla 4?

Answer 1

Assuming you are using the same code for J3, it's working by coincidence. The library is using PSR4 autoloading but in J3 JLoader::registerNamespace() defaults to PSR0. Normally this wouldn't work but you're also registering the wrong directory which ends up coinciding with how PSR0 library would be structured. Essentially, you need to switch to PSR4 autoloading for J3 (J4 supports only PSR4) and register the correct directory to make the code work for both J3 and J4:

JLoader::registerNamespace('EasyPost', JPATH_LIBRARIES. '/lib/EasyPost', false, false, 'psr4');

An alternative would be to include the lib/easypost.php file but that would be slower since it would load all class files even when they're not used. Additionally, this may stop working when the library becomes dependent on other libraries (i.e. like v6 does).