Set installing flag

core/backend/Engine/LegacyHandler/LegacyHandler.php

@@ -27,6 +27,7 @@
 
 namespace App\Engine\LegacyHandler;
 
+use App\Install\Service\InstallationUtilsTrait;
 use BeanFactory;
 use ControllerFactory;
 use RuntimeException;
@@ -41,6 +42,8 @@ use User;
  */
 abstract class LegacyHandler
 {
+    use InstallationUtilsTrait;
+
     protected const MSG_LEGACY_BOOTSTRAP_FAILED = 'Running legacy entry point failed';
 
     /**
@@ -134,6 +137,11 @@ abstract class LegacyHandler
             define('sugarEntry', true);
         }
 
+        if (!$this->isAppInstalled($this->legacyDir)) {
+            global $installing;
+            $installing = true;
+        }
+
         // Load in legacy
         /* @noinspection PhpIncludeInspection */
         require_once 'include/MVC/preDispatch.php';

core/backend/Install/LegacyHandler/InstallHandler.php

@@ -105,6 +105,9 @@ class InstallHandler extends LegacyHandler
     {
         $this->switchSession($this->legacySessionName);
         chdir($this->legacyDir);
+
+        global $installing;
+        $installing = true;
     }
 
     /**

core/backend/Install/Service/Installation/InstallActionHandler.php

@@ -126,6 +126,9 @@ class InstallActionHandler implements ProcessHandlerInterface
     {
         $options = $process->getOptions();
 
+        global $installing;
+        $installing = true;
+
         $result = $this->runSteps($this->getContext($options['payload'] ?? []));
 
         $this->setProcessData($process, $result);

core/backend/Languages/LegacyHandler/AppStringsHandler.php

@@ -113,6 +113,10 @@ class AppStringsHandler extends LegacyHandler
             return null;
         }
 
+        if (!$this->isInstalled()) {
+            return $this->getInstallAppStrings($language);
+        }
+
         $this->init();
 
         $enabledLanguages = get_languages();
@@ -157,6 +161,7 @@ class AppStringsHandler extends LegacyHandler
 
         $this->installHandler->initLegacy();
 
+        /* @noinspection PhpIncludeInspection */
         require_once 'include/utils.php';
 
         $appStringsArray = load_install_language($language) ?? [];
@@ -192,7 +197,6 @@ class AppStringsHandler extends LegacyHandler
         $moduleLanguage = return_module_language($language, $module, true);
 
         foreach ($languageKeys as $key) {
-
             if (isset($moduleLanguage[$key])) {
                 $appStringsArray[$key] = $moduleLanguage[$key];
             }
@@ -217,4 +221,12 @@ class AppStringsHandler extends LegacyHandler
 
         return $appStringsArray;
     }
+
+    /**
+     * @return bool
+     */
+    protected function isInstalled(): bool
+    {
+        return $this->installHandler->isAppInstalled($this->legacyDir);
+    }
 }