[BUGFIX] Do not reuse TemplateView instance when reading available pa…

…ge templates

Some change in TYPO3v12's Fluid dep has caused the TemplateParser to
hold on to invalid states of parsed templates. Likely has to do with the
many hoop-jumps the Fluid team has had to do since declaring that shared
ViewHelper instances is a totally valid use case.

I'm getting really tired of TYPO3's decisions as of late.

Classes/Service/PageService.php

@@ -229,8 +229,6 @@ public function getAvailablePageTemplateFiles(): array
         $typoScript = $this->getPageConfiguration();
         $output = [];
 
-        /** @var TemplateView $view */
-        $view = GeneralUtility::makeInstance(TemplateView::class);
         foreach ((array) $typoScript as $extensionName => $group) {
             if (!($group['enable'] ?? true)) {
                 continue;
@@ -251,6 +249,8 @@ public function getAvailablePageTemplateFiles(): array
                     continue;
                 }
 
+                /** @var TemplateView $view */
+                $view = GeneralUtility::makeInstance(TemplateView::class);
                 $view->getRenderingContext()->setTemplatePaths($templatePaths);
                 $view->getRenderingContext()->getViewHelperVariableContainer()->addOrUpdate(
                     FormViewHelper::SCOPE,

Tests/Unit/Service/PageServiceTest.php

@@ -121,6 +121,8 @@ public function testGetAvailablePageTemplateFiles($typoScript, $expected): void
         $instance->method('createTemplatePaths')->willReturn($templatePaths);
         $instance->method('getPageConfiguration')->willReturn($typoScript);
 
+        // There are exactly 2 page template fixtures. We need to return exactly two mock instances of TemplateView.
+        GeneralUtility::addInstance(TemplateView::class, $templateView);
         GeneralUtility::addInstance(TemplateView::class, $templateView);
 
         $result = $instance->getAvailablePageTemplateFiles();