[5.1] SEF: Implementing trailing slash behavior

administrator/language/en-GB/plg_system_sef.ini

@@ -5,5 +5,11 @@
 
 PLG_SEF_DOMAIN_DESCRIPTION="If your site can be accessed through more than one domain enter the preferred (sometimes referred to as canonical) domain here. <br><strong>Note:</strong> https://example.com and https://www.example.com are different domains."
 PLG_SEF_DOMAIN_LABEL="Site Domain"
+PLG_SEF_TRAILINGSLASH_DESCRIPTION="Force Joomla to only create URLs with or without trailing slash. This is only applied when 'Add suffix to URL' is disabled."
+PLG_SEF_TRAILINGSLASH_LABEL="Trailing slash handling of URLs"
+PLG_SEF_TRAILINGSLASH_OPTION_NONE="No change"
+PLG_SEF_TRAILINGSLASH_OPTION_NO_SLASH="Only create URLs without trailing slash"
+PLG_SEF_TRAILINGSLASH_OPTION_SLASH="Always enforce a trailing slash"
+PLG_SEF_TRAILINGSLASH_REDIRECT_LABEL="Enforce slash behavior with a 301 redirect"
 PLG_SEF_XML_DESCRIPTION="Adds SEF support to links in the document. It operates directly on the HTML and does not require a special tag."
 PLG_SYSTEM_SEF="System - SEF"

plugins/system/sef/sef.xml

@@ -30,6 +30,32 @@
 					filter="url"
 					validate="url"
 				/>
+
+				<field
+					name="trailingslash"
+					type="list"
+					label="PLG_SEF_TRAILINGSLASH_LABEL"
+					description="PLG_SEF_TRAILINGSLASH_DESCRIPTION"
+					default="0"
+					filter="option"
+				>
+					<option value="0">PLG_SEF_TRAILINGSLASH_OPTION_NONE</option>
+					<option value="1">PLG_SEF_TRAILINGSLASH_OPTION_NO_SLASH</option>
+					<option value="2">PLG_SEF_TRAILINGSLASH_OPTION_SLASH</option>
+				</field>
+
+				<field
+					name="trailingslash_redirect"
+					type="radio"
+					label="PLG_SEF_TRAILINGSLASH_REDIRECT_LABEL"
+					layout="joomla.form.field.radio.switcher"
+					default="0"
+					filter="boolean"
+					showon="trailingslash:1,2"
+				>
+					<option value="0">JNO</option>
+					<option value="1">JYES</option>
+				</field>
 			</fieldset>
 		</fields>
 	</config>

plugins/system/sef/src/Extension/Sef.php

@@ -10,9 +10,13 @@
 
 namespace Joomla\Plugin\System\Sef\Extension;
 
+use Joomla\CMS\Event\Router\AfterInitialiseRouterEvent;
 use Joomla\CMS\Plugin\CMSPlugin;
 use Joomla\CMS\Router\Route;
+use Joomla\CMS\Router\Router;
+use Joomla\CMS\Router\SiteRouter;
 use Joomla\CMS\Uri\Uri;
+use Joomla\Event\SubscriberInterface;
 
 // phpcs:disable PSR1.Files.SideEffects
 \defined('_JEXEC') or die;
@@ -23,8 +27,67 @@
  *
  * @since  1.5
  */
-final class Sef extends CMSPlugin
+final class Sef extends CMSPlugin implements SubscriberInterface
 {
+    /**
+     * Application object.
+     *
+     * @var    \Joomla\CMS\Application\CMSApplication
+     * @since  __DEPLOY_VERSION__
+     */
+    protected $app;
+
+    /**
+     * Returns an array of CMS events this plugin will listen to and the respective handlers.
+     *
+     * @return  array
+     *
+     * @since  __DEPLOY_VERSION__
+     */
+    public static function getSubscribedEvents(): array
+    {
+        /**
+         * Note that onAfterInitialise must be the first handlers to run for this
+         * plugin to operate as expected. These handlers load compatibility code which
+         * might be needed by other plugins
+         */
+        return [
+            'onAfterInitialiseRouter' => 'onAfterInitialiseRouter',
+            'onAfterDispatch'         => 'onAfterDispatch',
+            'onAfterRender'           => 'onAfterRender',
+        ];
+    }
+
+    /**
+     * After initialise router.
+     *
+     * @return  void
+     *
+     * @since   __DEPLOY_VERSION__
+     */
+    public function onAfterInitialiseRouter(AfterInitialiseRouterEvent $event)
+    {
+        if (
+            !is_a($event->getRouter(), SiteRouter::class)
+            || $this->app->get('sef_suffix')
+        ) {
+            return;
+        }
+
+        if ($this->params->get('trailingslash') == 1) {
+            // Remove trailingslash
+            $event->getRouter()->attachBuildRule([$this, 'removeTrailingSlash'], SiteRouter::PROCESS_AFTER);
+        } elseif ($this->params->get('trailingslash') == 2) {
+            // Add trailingslash
+            $event->getRouter()->attachBuildRule([$this, 'addTrailingSlash'], SiteRouter::PROCESS_AFTER);
+        }
+
+        if ($this->params->get('trailingslash') && $this->params->get('trailingslash_redirect')) {
+            // Enforce trailingslash
+            $event->getRouter()->attachParseRule([$this, 'enforceTrailingSlash'], SiteRouter::PROCESS_BEFORE);
+        }
+    }
+
     /**
      * Add the canonical uri to the head.
      *
@@ -188,6 +251,74 @@ function ($match) use ($base, $protocols) {
         $this->getApplication()->setBody($buffer);
     }
 
+    /**
+     * Remove any trailing slash from URLs built in Joomla
+     *
+     * @param   Router  &$router  Router object.
+     * @param   Uri     &$uri     Uri object.
+     *
+     * @return  void
+     *
+     * @since   __DEPLOY_VERSION__
+     */
+    public function removeTrailingSlash(&$router, &$uri)
+    {
+        $path = $uri->getPath();
+
+        if (substr($path, -1) == '/') {
+            $uri->setPath(substr($path, 0, -1));
+        }
+    }
+
+    /**
+     * Add trailing slash to URLs built in Joomla
+     *
+     * @param   Router  &$router  Router object.
+     * @param   Uri     &$uri     Uri object.
+     *
+     * @return  void
+     *
+     * @since   __DEPLOY_VERSION__
+     */
+    public function addTrailingSlash(&$router, &$uri)
+    {
+        $path = $uri->getPath();
+
+        if (substr($path, -1) !== '/') {
+            $uri->setPath($path . '/');
+        }
+    }
+
+    /**
+     * Redirect to a URL with or without trailing slash
+     *
+     * @param   Router  &$router  Router object.
+     * @param   Uri     &$uri     Uri object.
+     *
+     * @return  void
+     *
+     * @since   __DEPLOY_VERSION__
+     */
+    public function enforceTrailingSlash(&$router, &$uri)
+    {
+        // We only want to redirect on GET requests
+        if ($this->app->getInput()->getMethod() != 'GET') {
+            return;
+        }
+
+        $originalUri = Uri::getInstance();
+
+        if ($this->params->get('trailingslash') == 1 && substr($originalUri->getPath(), -1) == '/') {
+            // Remove trailingslash
+            $originalUri->setPath(substr($originalUri->getPath(), 0, -1));
+            $this->app->redirect($originalUri->toString());
+        } elseif ($this->params->get('trailingslash') == 2 && substr($originalUri->getPath(), -1) != '/') {
+            // Add trailingslash
+            $originalUri->setPath($originalUri->getPath() . '/');
+            $this->app->redirect($originalUri->toString());
+        }
+    }
+
     /**
      * Check the buffer.
      *