[5.2] SEF: Enforce suffix

administrator/language/en-GB/plg_system_sef.ini

@@ -5,6 +5,8 @@
 
 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_ENFORCESUFFIX_DESCRIPTION="When enabled and \"Add Suffix to URL\" is also enabled, URLs without suffix will be redirected to the correct one. From version 6.0 onwards this will be the standard behavior and not an option anymore."
+PLG_SEF_ENFORCESUFFIX_LABEL="Enforce a suffix by redirect"
 PLG_SEF_INDEXPHP_DESCRIPTION="This option enables a stricter handling of 'index.php' in URLs when 'Use URL Rewriting' is enabled in Global Configuration. It will remove 'index.php' if a URL still contains it and redirect incoming requests with 'index.php' to the version without the 'index.php'."
 PLG_SEF_INDEXPHP_LABEL="Strict handling of index.php"
 PLG_SEF_STRICTROUTING_DESCRIPTION="Prevent the router from accepting a lot of URLs which are deemed as duplicates and will automatically redirect to the correct URL with a 301."

plugins/system/sef/sef.xml

@@ -31,6 +31,19 @@
 					validate="url"
 				/>
 
+				<field
+					name="enforcesuffix"
+					type="list"
+					label="PLG_SEF_ENFORCESUFFIX_LABEL"
+					description="PLG_SEF_ENFORCESUFFIX_DESCRIPTION"
+					layout="joomla.form.field.radio.switcher"
+					default="0"
+					filter="boolean"
+				>
+					<option value="0">JNO</option>
+					<option value="1">JYES</option>
+				</field>
+
 				<field
 					name="indexphp"
 					type="radio"

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

@@ -110,6 +110,11 @@ public function onAfterRoute()
             $this->enforceTrailingSlash();
         }
 
+        // Enforce adding a suffix with a redirect
+        if ($app->get('sef') && $app->get('sef_suffix') && $this->params->get('enforcesuffix')) {
+            $this->enforceSuffix();
+        }
+
         // Enforce SEF URLs
         if ($this->params->get('strictrouting') && $app->getInput()->getMethod() == 'GET') {
             $this->enforceSEF();
@@ -279,6 +284,48 @@ function ($match) use ($base, $protocols) {
         $this->getApplication()->setBody($buffer);
     }
 
+    /**
+     * Enforce the URL suffix with a redirect
+     *
+     * @return  void
+     *
+     * @since   __DEPLOY_VERSION__
+     */
+    public function enforceSuffix()
+    {
+        $origUri = Uri::getInstance();
+        $route   = $origUri->getPath();
+
+        if (substr($route, -9) === 'index.php' || substr($route, -1) === '/') {
+            // We don't want suffixes when the URL ends in index.php or with a /
+            return;
+        }
+
+        $suffix       = pathinfo($route, PATHINFO_EXTENSION);
+        $nonSEFSuffix = $origUri->getVar('format');
+
+        if ($nonSEFSuffix && $suffix !== $nonSEFSuffix) {
+            // There is a URL query parameter named "format", which isn't the same to the suffix
+            $pathWithoutSuffix = ($suffix !== '') ? substr($route, 0, -(\strlen($suffix) + 1)) : $route;
+
+            $origUri->delVar('format');
+            $origUri->setPath($pathWithoutSuffix . '.' . $nonSEFSuffix);
+            $this->getApplication()->redirect($origUri->toString(), 301);
+        }
+
+        if ($suffix && $suffix == $nonSEFSuffix) {
+            // There is a URL query parameter named "format", which is identical to the suffix
+            $origUri->delVar('format');
+            $this->getApplication()->redirect($origUri->toString(), 301);
+        }
+
+        if (!$suffix) {
+            // We don't have a suffix, so we default to .html at the end
+            $origUri->setPath($route . '.html');
+            $this->getApplication()->redirect($origUri->toString(), 301);
+        }
+    }
+
     /**
      * Enforce removal of index.php with a redirect
      *