"Failed to start application" on Joomla 4

[Openuser87]

When trying to use the script after upgrade from Joomla 3.10 to 4.40, it failed with

Exception: Failed to start application

Error occured in line 64:

$app = JFactory::getApplication('site');

The exception has been thrown here:

<joomla_dir>/libraries/src/Factory.php:158

     * @throws  \Exception
     */
    public static function getApplication()
    {
        if (!self::$application) {
            throw new \Exception('Failed to start application', 500);
        }
        return self::$application;
    }

Can it be that the way of starting scripts in Joomla has changed somewhere between the versions?

I was able to fix the issue by applying the approach taken here, also considering this post.

After replacing the lines 63-64 with following code, script worked as expected:

    // Instantiate the application.
    $container = \Joomla\CMS\Factory::getContainer();

    $container->alias('session.web', 'session.web.site')
	->alias('session', 'session.web.site')
	->alias('JSession', 'session.web.site')
	->alias(\Joomla\CMS\Session\Session::class, 'session.web.site')
	->alias(\Joomla\Session\Session::class, 'session.web.site')
	->alias(\Joomla\Session\SessionInterface::class, 'session.web.site');

	$app    = $container->get(\Joomla\CMS\Application\SiteApplication::class);

This is of course a "workaround" only, I am not a developer and am not sure about the appropriateness of the code, except that it worked ;).

Can this be addressed / incorporated into some fix?

The script solved my problem by the way, thank you very much! :)