[BUGFIX] Simulate TSFE while processing variables

As mail will be sent by scheduler (BE context), we
do not have a TSFE. If working with TS Variables these
require a working TSFE. Adding a temporary TSFE
like in f:cObject VH solves that problem.

Resolves: in2code-de#45

Classes/Domain/Service/ParseNewsletterUrlService.php

@@ -19,6 +19,7 @@
 use TYPO3\CMS\Extbase\SignalSlot\Exception\InvalidSlotException;
 use TYPO3\CMS\Extbase\SignalSlot\Exception\InvalidSlotReturnException;
 use TYPO3\CMS\Fluid\View\StandaloneView;
+use TYPO3\CMS\Frontend\Controller\TypoScriptFrontendController;
 
 /**
  * Class ParseNewsletterUrlService to fill a container html with a content from a http(s) page.
@@ -42,6 +43,13 @@ class ParseNewsletterUrlService
      */
     protected $parseVariables = true;
 
+    /**
+     * Contains a backup of the current $GLOBALS['TSFE'] if used in BE mode
+     *
+     * @var TypoScriptFrontendController
+     */
+    protected static $tsfeBackup;
+
     /**
      * ParseNewsletterUrlService constructor.
      * @param string $origin can be a page uid or a complete url
@@ -144,6 +152,9 @@ protected function getNewsletterContainerAndContent(string $content, User $user)
      */
     protected function getContentObjectVariables(array $configuration): array
     {
+        if (TYPO3_MODE === 'BE') {
+            self::simulateFrontendEnvironment();
+        }
         $tsService = ObjectUtility::getObjectManager()->get(TypoScriptService::class);
         $tsConfiguration = $tsService->convertPlainArrayToTypoScriptArray($configuration);
 
@@ -161,6 +172,10 @@ protected function getContentObjectVariables(array $configuration): array
             );
         }
 
+        if (TYPO3_MODE === 'BE') {
+            self::resetFrontendEnvironment();
+        }
+
         return $variables;
     }
 
@@ -219,6 +234,28 @@ protected function getBodyFromHtml(string $string): string
         return $string;
     }
 
+    /**
+     * Sets the $TSFE->cObjectDepthCounter in Backend mode
+     * This somewhat hacky work around is currently needed because the cObjGetSingle() function of \TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer relies on this setting
+     */
+    protected static function simulateFrontendEnvironment()
+    {
+        static::$tsfeBackup = $GLOBALS['TSFE'] ?? null;
+        $GLOBALS['TSFE'] = new \stdClass();
+        $GLOBALS['TSFE']->cObj = ObjectUtility::getContentObject();
+        $GLOBALS['TSFE']->cObjectDepthCounter = 100;
+    }
+
+    /**
+     * Resets $GLOBALS['TSFE'] if it was previously changed by simulateFrontendEnvironment()
+     *
+     * @see simulateFrontendEnvironment()
+     */
+    protected static function resetFrontendEnvironment()
+    {
+        $GLOBALS['TSFE'] = static::$tsfeBackup;
+    }
+
     /**
      * @return bool
      */