[BUGFIX] Allow overriding of Backend Routes

Adding backend routes from Configuration/Backend/Routes.php is
done via "+=" operator which does not allow to override routes with
the same name. This is however a wanted behaviour - allowing extensions
to override core routes.

The patch changes the "+=" operator to a simple array_merge() call
to allow to change existing routes.

Resolves: #74004
Releases: master, 7.6
Change-Id: I7caf1ab5a91f849b4789ea352c20af6239470f2f
Reviewed-on: https://review.typo3.org/47005


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Thomas Schlumberger <thomas@b13.de>
Tested-by: Thomas Schlumberger <thomas@b13.de>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>

typo3/sysext/core/Classes/Core/Bootstrap.php

@@ -1010,8 +1010,6 @@ class Bootstrap
      */
     public function initializeBackendRouter()
     {
-        $packageManager = $this->getEarlyInstance(\TYPO3\CMS\Core\Package\PackageManager::class);
-
         // See if the Routes.php from all active packages have been built together already
         $cacheIdentifier = 'BackendRoutesFromPackages_' . sha1((TYPO3_version . PATH_site . 'BackendRoutesFromPackages'));
 
@@ -1023,13 +1021,14 @@ class Bootstrap
             $routesFromPackages = unserialize(substr($codeCache->get($cacheIdentifier), 6, -2));
         } else {
             // Loop over all packages and check for a Configuration/Backend/Routes.php file
+            $packageManager = $this->getEarlyInstance(\TYPO3\CMS\Core\Package\PackageManager::class);
             $packages = $packageManager->getActivePackages();
             foreach ($packages as $package) {
                 $routesFileNameForPackage = $package->getPackagePath() . 'Configuration/Backend/Routes.php';
                 if (file_exists($routesFileNameForPackage)) {
                     $definedRoutesInPackage = require $routesFileNameForPackage;
                     if (is_array($definedRoutesInPackage)) {
-                        $routesFromPackages += $definedRoutesInPackage;
+                        $routesFromPackages = array_merge($routesFromPackages, $definedRoutesInPackage);
                     }
                 }
                 $routesFileNameForPackage = $package->getPackagePath() . 'Configuration/Backend/AjaxRoutes.php';