[BUGFIX] Preserve parent ViewHelperVariableContainer in ComponentRend…

src/Core/Component/ComponentRenderer.php

@@ -10,7 +10,6 @@
 namespace TYPO3Fluid\Fluid\Core\Component;
 
 use TYPO3Fluid\Fluid\Core\Rendering\RenderingContextInterface;
-use TYPO3Fluid\Fluid\Core\ViewHelper\ViewHelperVariableContainer;
 use TYPO3Fluid\Fluid\View\TemplateView;
 use TYPO3Fluid\Fluid\ViewHelpers\SlotViewHelper;
 
@@ -36,14 +35,29 @@ public function renderComponent(string $viewHelperName, array $arguments, array
         $renderingContext->setViewHelperResolver($renderingContext->getViewHelperResolver()->getScopedCopy());
         $renderingContext->setVariableProvider($renderingContext->getVariableProvider()->getScopeCopy($arguments));
 
-        // Provide slots to SlotViewHelper
-        $renderingContext->setViewHelperVariableContainer(new ViewHelperVariableContainer());
-        $renderingContext->getViewHelperVariableContainer()->addAll(SlotViewHelper::class, $slots);
+        // Provide slots to SlotViewHelper while preserving the parent ViewHelperVariableContainer
+        // so that context set by outer ViewHelpers (e.g. TYPO3's FormViewHelper) remains available
+        // inside components. Slot state is saved and restored to support proper component nesting.
+        $parentVhvc = $parentRenderingContext->getViewHelperVariableContainer();
+        $previousSlots = $parentVhvc->getAll(SlotViewHelper::class);
+        foreach ($slots as $slotName => $slotClosure) {
+            $parentVhvc->addOrUpdate(SlotViewHelper::class, $slotName, $slotClosure);
+        }
+        $renderingContext->setViewHelperVariableContainer($parentVhvc);
 
         // Create Fluid view for component
         // render() call includes validation of provided arguments
         $view = new TemplateView($renderingContext);
         $view->assignMultiple($this->componentResolver->getAdditionalVariables($viewHelperName));
-        return (string)$view->render($this->componentResolver->resolveTemplateName($viewHelperName));
+        $result = (string)$view->render($this->componentResolver->resolveTemplateName($viewHelperName));
+
+        // Restore previous slot state so that outer components can still access their own slots.
+        foreach (array_keys($slots) as $slotName) {
+            $parentVhvc->remove(SlotViewHelper::class, $slotName);
+            if (array_key_exists($slotName, $previousSlots)) {
+                $parentVhvc->addOrUpdate(SlotViewHelper::class, $slotName, $previousSlots[$slotName]);
+            }
+        }
+        return $result;
     }
 }

tests/Functional/Core/Component/ComponentViewHelperVariableContainerTest.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file belongs to the package "TYPO3 Fluid".
+ * See LICENSE.txt that was shipped with this package.
+ */
+
+namespace TYPO3Fluid\Fluid\Tests\Functional\Core\Component;
+
+use PHPUnit\Framework\Attributes\Test;
+use TYPO3Fluid\Fluid\Tests\Functional\AbstractFunctionalTestCase;
+use TYPO3Fluid\Fluid\View\TemplateView;
+
+/**
+ * Verifies that ViewHelpers rendered inside a component can still access ViewHelperVariableContainer
+ * state set up by an outer ViewHelper (e. g. a form ViewHelper), matching the behavior components need
+ * to be usable as drop-in replacements for sitegeist/fluid-components.
+ */
+final class ComponentViewHelperVariableContainerTest extends AbstractFunctionalTestCase
+{
+    private function renderTemplate(string $source): string
+    {
+        $view = new TemplateView();
+        $view->getRenderingContext()->setCache(self::$cache);
+        $view->getRenderingContext()->getViewHelperResolver()->addNamespace('my', 'TYPO3Fluid\Fluid\Tests\Functional\Fixtures\ComponentCollections\BasicComponentCollection');
+        $view->getRenderingContext()->getViewHelperResolver()->addNamespace('formComponent', 'TYPO3Fluid\Fluid\Tests\Functional\Fixtures\ComponentCollections\FormComponentCollection');
+        $view->getRenderingContext()->getViewHelperResolver()->addNamespace('form', 'TYPO3Fluid\Fluid\Tests\Functional\Fixtures\ViewHelpers\MockForm');
+        $view->getRenderingContext()->getTemplatePaths()->setTemplateSource($source);
+        return $view->render();
+    }
+
+    #[Test]
+    public function outerViewHelperContextIsAvailableInsideComponent(): void
+    {
+        $source = '<form:context><formComponent:formFieldComponent name="field1" /></form:context>';
+        $expected = '<input name="field1" />' . "\n" . '|fieldNames:field1';
+
+        self::assertSame($expected, $this->renderTemplate($source), 'uncached');
+        self::assertSame($expected, $this->renderTemplate($source), 'cached');
+    }
+
+    #[Test]
+    public function fieldViewHelperWithoutOuterContextRendersWithoutIt(): void
+    {
+        $source = '<formComponent:formFieldComponent name="field1" />';
+        $expected = '<input name="field1" without-context />' . "\n";
+
+        self::assertSame($expected, $this->renderTemplate($source), 'uncached');
+        self::assertSame($expected, $this->renderTemplate($source), 'cached');
+    }
+
+    #[Test]
+    public function multipleComponentsInsideOuterContextAllRegisterThemselves(): void
+    {
+        $source = '<form:context><formComponent:formFieldComponent name="field1" /><formComponent:formFieldComponent name="field2" /></form:context>';
+        $expected = '<input name="field1" />' . "\n" . '<input name="field2" />' . "\n" . '|fieldNames:field1,field2';
+
+        self::assertSame($expected, $this->renderTemplate($source), 'uncached');
+        self::assertSame($expected, $this->renderTemplate($source), 'cached');
+    }
+
+    #[Test]
+    public function nestedComponentSlotsRemainIsolatedWhileSharingOuterContext(): void
+    {
+        $source = '<form:context><my:namedSlots><f:fragment name="test1"><formComponent:formFieldComponent name="field1" /></f:fragment></my:namedSlots></form:context>';
+        $expected = '|<input name="field1" />' . "\n" . '|||' . "\n" . '|fieldNames:field1';
+
+        self::assertSame($expected, $this->renderTemplate($source), 'uncached');
+        self::assertSame($expected, $this->renderTemplate($source), 'cached');
+    }
+}

tests/Functional/Fixtures/ComponentCollections/FormComponentCollection.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file belongs to the package "TYPO3 Fluid".
+ * See LICENSE.txt that was shipped with this package.
+ */
+
+namespace TYPO3Fluid\Fluid\Tests\Functional\Fixtures\ComponentCollections;
+
+use TYPO3Fluid\Fluid\Core\Component\AbstractComponentCollection;
+use TYPO3Fluid\Fluid\View\TemplatePaths;
+
+final class FormComponentCollection extends AbstractComponentCollection
+{
+    public function getTemplatePaths(): TemplatePaths
+    {
+        $templatePaths = new TemplatePaths();
+        $templatePaths->setTemplateRootPaths([
+            __DIR__ . '/FormComponents/',
+        ]);
+        return $templatePaths;
+    }
+}

tests/Functional/Fixtures/ComponentCollections/FormComponents/FormFieldComponent/FormFieldComponent.html

@@ -0,0 +1 @@
+<f:argument name="name" type="string" /><form:field name="{name}" />

tests/Functional/Fixtures/ViewHelpers/MockForm/ContextViewHelper.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file belongs to the package "TYPO3 Fluid".
+ * See LICENSE.txt that was shipped with this package.
+ */
+
+namespace TYPO3Fluid\Fluid\Tests\Functional\Fixtures\ViewHelpers\MockForm;
+
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;
+
+/**
+ * Minimal stand-in for a form ViewHelper (such as TYPO3's FormViewHelper) that stores state in the
+ * ViewHelperVariableContainer for nested field ViewHelpers to consume, e. g. to collect field names
+ * for "trustedProperties". Used to test that this context remains available inside components.
+ */
+final class ContextViewHelper extends AbstractViewHelper
+{
+    protected $escapeOutput = false;
+
+    public function render(): string
+    {
+        $variableContainer = $this->renderingContext->getViewHelperVariableContainer();
+        $variableContainer->addOrUpdate(self::class, 'fieldNames', []);
+
+        $content = $this->renderChildren();
+
+        $fieldNames = $variableContainer->get(self::class, 'fieldNames', []);
+        $variableContainer->remove(self::class, 'fieldNames');
+
+        return $content . '|fieldNames:' . implode(',', $fieldNames);
+    }
+}

tests/Functional/Fixtures/ViewHelpers/MockForm/FieldViewHelper.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file belongs to the package "TYPO3 Fluid".
+ * See LICENSE.txt that was shipped with this package.
+ */
+
+namespace TYPO3Fluid\Fluid\Tests\Functional\Fixtures\ViewHelpers\MockForm;
+
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;
+
+/**
+ * Minimal stand-in for a form field ViewHelper (such as TYPO3's TextfieldViewHelper) that reads
+ * context from a surrounding ContextViewHelper via the ViewHelperVariableContainer and registers
+ * its name for "trustedProperties". Used to test that this context remains available inside components.
+ */
+final class FieldViewHelper extends AbstractViewHelper
+{
+    protected $escapeOutput = false;
+
+    public function initializeArguments(): void
+    {
+        $this->registerArgument('name', 'string', 'Field name', true);
+    }
+
+    public function render(): string
+    {
+        $name = $this->arguments['name'];
+        $variableContainer = $this->renderingContext->getViewHelperVariableContainer();
+
+        if (!$variableContainer->exists(ContextViewHelper::class, 'fieldNames')) {
+            return sprintf('<input name="%s" without-context />', $name);
+        }
+
+        $fieldNames = $variableContainer->get(ContextViewHelper::class, 'fieldNames');
+        $fieldNames[] = $name;
+        $variableContainer->addOrUpdate(ContextViewHelper::class, 'fieldNames', $fieldNames);
+
+        return sprintf('<input name="%s" />', $name);
+    }
+}