[BUGFIX] Use matching site in extbase BE modules

Extbase BE modules suffer from the conceptual mistake
of using FE TypoScript for configuration. Modules
not in page context pick the first root template
in the page tree as TS entry point.

The patch changes this awful handling to also use
the attached site object for this page to substitute
site settings used as constants in TS correctly.

Resolves: #102452
Related: #97816
Releases: main, 12.4
Change-Id: I24e1e814cd20fc4999311d4f0068fb51818ad611
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82558


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/extbase/Classes/Configuration/BackendConfigurationManager.php

@@ -26,7 +26,10 @@ use TYPO3\CMS\Core\Database\ConnectionPool;
 use TYPO3\CMS\Core\Database\Query\QueryHelper;
 use TYPO3\CMS\Core\Database\Query\Restriction\DeletedRestriction;
 use TYPO3\CMS\Core\Database\Query\Restriction\HiddenRestriction;
+use TYPO3\CMS\Core\Exception\SiteNotFoundException;
 use TYPO3\CMS\Core\SingletonInterface;
+use TYPO3\CMS\Core\Site\Entity\NullSite;
+use TYPO3\CMS\Core\Site\SiteFinder;
 use TYPO3\CMS\Core\Type\Bitmask\Permission;
 use TYPO3\CMS\Core\TypoScript\IncludeTree\SysTemplateRepository;
 use TYPO3\CMS\Core\TypoScript\IncludeTree\SysTemplateTreeBuilder;
@@ -107,6 +110,7 @@ class BackendConfigurationManager implements SingletonInterface
         private readonly SysTemplateTreeBuilder $treeBuilder,
         private readonly LossyTokenizer $lossyTokenizer,
         private readonly ConditionVerdictAwareIncludeTreeTraverser $includeTreeTraverserConditionVerdictAware,
+        private readonly SiteFinder $siteFinder,
     ) {}
 
     public function setRequest(ServerRequestInterface $request): void
@@ -221,6 +225,19 @@ class BackendConfigurationManager implements SingletonInterface
         }
 
         $site = $request?->getAttribute('site');
+        if (($site === null || $site instanceof NullSite) && $pageId > 0) {
+            // Due to the weird magic of getting the pid of the first root template when
+            // not having a pageId (extbase BE modules without page tree / no page selected),
+            // we also have no proper site in this case.
+            // So we try to get the site for this pageId. This way, site settings for this
+            // first TS page are turned into constants and can be used in setup and setup
+            // conditions.
+            try {
+                $site = $this->siteFinder->getSiteByPageId($pageId);
+            } catch (SiteNotFoundException) {
+                // Keep null / NullSite when no site could be determined for whatever reason.
+            }
+        }
 
         $rootLine = [];
         $sysTemplateFakeRow = [