onAfterRender plugin only triggers on backend

Question

I have created a system plugin for onAfterRender event however I'm unable to make it execute. I'm on Joomla 3.9

Here's the sample code of the plugin

    <?xml version="1.0" encoding="utf-8"?>
    <!--
    /**
     * @copyright   Copyright (c) 2018 myvendorcustomscripts. All rights reserved.
     * @license     http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL
     */
    -->
    <extension type="plugin" version="1.0" group="content" method="upgrade">
        <name>plg_system_myvendorcustomscripts</name>
        <author>myvendor</author>
        <creationDate>October 2018</creationDate>
        <copyright>Copyright (c) 2018 myvendorcustomscripts. All rights reserved.</copyright>
        <license>http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL</license>
        <authorEmail></authorEmail>
        <authorUrl></authorUrl>
        <version>1.0.0</version>
        <description>
        <![CDATA[

        ]]>
        </description>

        <files>
            <filename plugin="myvendorcustomscripts">myvendorcustomscripts.php</filename>
            <filename>index.html</filename>
        </files>

        <languages>
            <language tag="en-GB">en-GB.plg_system_myvendorcustomscripts.ini</language>
            <language tag="en-GB">en-GB.plg_system_myvendorcustomscripts.sys.ini</language>
        </languages>

        <config>
            <fields name="params">
                <fieldset name="basic">

                </fieldset>
            </fields>
        </config>
    </extension>

And

        <?php
        /**
         * @copyright    Copyright (c) 2018 myvendorcustomscripts. All rights reserved.
         * @license        http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL
         */

    // no direct access
        defined('_JEXEC') or die;

        jimport('joomla.plugin.plugin');

        /**
         * content - MyVendorCustomScripts Plugin
         *
         * @package        Joomla.Plugin
         * @subpakage    myvendorcustomscripts.MyVendorCustomScripts
         * @since
         */
        class plgSystemMyVendorCustomScripts extends JPlugin
        {
            /**
             * Constructor.
             *
             * @param    $subject
             * @param    array $config
             * @since
             */
            public function __construct(&$subject, $config = array())
            {
                // call parent constructor
                parent::__construct($subject, $config);
            }


            public function onAfterRender()
            {
                $app = JFactory::getApplication();

            }


            public function onBeforeCompileHead()
            {
                $app = JFactory::getApplication();
                $document = $app->getDocument();

                foreach ($document->_styleSheets as $index => $value) {
                    if (strpos($index, 'fonts.googleapis.com')) {
                        unset($document->_styleSheets[$index]);
                    }

                    if (strpos($index, 'simple-line-icons')) {
                        unset($document->_styleSheets[$index]);
                    }

    //                $styleSheet = $styleSheet;
                }
            }
        }

However the functions never get executed when I'm browsing the frontend but they do get executed when browsing the backend. It's really strange and I can't understand the reason. It seems on the documentation that this even should trigger always

Answer 1

The code you currently have works. You just need to clear page cache and view the page again. You'll see fonts.googleapis.com links are removed. This may or may not be fine depending on the rest of your code.

When System - Page Cache plugin is enabled, on first load page (determined by URL) on is rendered normally with all expected plugin events triggered and stored to cache during onAfterRespond event. On following page loads the plugin fetches the page from cache, pushes it to application and closes the application. This happens during onAfterInitialise event. No further events are triggered. Except onAfterRespond if debug is enabled.

The code you currently have in onBeforeCompileHead actually works fine because your changes are applied before the page is stored to cache.

However, in case you want to add code that is not cache-safe, e.g. code that changes from visitor to visitor or some randomly generated code, you could selectively disable cache using onPageCacheSetCaching event.