[FEATURE] Ignore Fluid syntax error in <f:comment>

This patch enables a template processor included in Fluid 4
for all Fluid instances in the Core. The template processor
strips `<f:comment>` tags from Fluid template strings before
the parsing starts. This prevents Fluid errors when invalid
Fluid code is used inside `<f:comment>`.

Original change in Fluid:
https://github.com/TYPO3/Fluid/commit/faad81a9f5d991d688e1d4c673e0d7aaf41a7e94

Resolves: #104904
Releases: main
Change-Id: Ieebb60ee21ae9f8d6f168e75b9fd22a7103a5f6a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/86012


Reviewed-by: Guido Schmechel <guido.schmechel@brandung.de>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Simon Praetorius <simon@praetorius.me>
Reviewed-by: Simon Praetorius <simon@praetorius.me>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/core/Configuration/DefaultConfiguration.php

@@ -364,6 +364,7 @@ return [
                 \TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\EscapingModifierTemplateProcessor::class,
                 \TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\PassthroughSourceModifierTemplateProcessor::class,
                 \TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\NamespaceDetectionTemplateProcessor::class,
+                \TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\RemoveCommentsTemplateProcessor::class,
             ],
             'expressionNodeTypes' => [
                 \TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression\CastingExpressionNode::class,

typo3/sysext/core/Documentation/Changelog/13.3/Feature-104904-IgnoreFluidSyntaxErrorInFComment.rst

+.. include:: /Includes.rst.txt
+
+.. _feature-104904-1726049662:
+
+===========================================================
+Feature: #104904 - Ignore Fluid syntax error in <f:comment>
+===========================================================
+
+See :issue:`104904`
+
+Description
+===========
+
+Fluid 4 brings a new template processor
+:php:`TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\RemoveCommentsTemplateProcessor`
+which removes Fluid comments created with :html:`<f:comment>` from the template source
+string before the parsing process starts. It retains the original line breaks to ensure
+that error messages still refer to the correct line in the template.
+
+By applying this template processor to all Fluid instances in the Core, it is now
+possible to use invalid Fluid code inside :html:`<f:comment>` without triggering a Fluid error.
+
+
+Impact
+======
+
+This feature is helpful during template development because developers don't need to
+take care for commented-out code being valid Fluid code.
+
+.. index:: Fluid, ext:fluid

typo3/sysext/fluid/Classes/Core/Rendering/RenderingContextFactory.php

@@ -27,6 +27,7 @@ use TYPO3Fluid\Fluid\Core\Cache\FluidCacheInterface;
 use TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\EscapingModifierTemplateProcessor;
 use TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\NamespaceDetectionTemplateProcessor;
 use TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\PassthroughSourceModifierTemplateProcessor;
+use TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\RemoveCommentsTemplateProcessor;
 use TYPO3Fluid\Fluid\Core\Parser\TemplateProcessorInterface;
 
 /**
@@ -68,6 +69,7 @@ final readonly class RenderingContextFactory
                 new EscapingModifierTemplateProcessor(),
                 new PassthroughSourceModifierTemplateProcessor(),
                 new NamespaceDetectionTemplateProcessor(),
+                new RemoveCommentsTemplateProcessor(),
             ];
         } else {
             foreach ($GLOBALS['TYPO3_CONF_VARS']['SYS']['fluid']['preProcessors'] as $className) {

typo3/sysext/fluid/Configuration/Services.yaml

@@ -39,3 +39,7 @@ services:
   TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\NamespaceDetectionTemplateProcessor:
     public: true
     shared: false
+  TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\RemoveCommentsTemplateProcessor:
+    public: true
+    shared: false
+