Feature: #79140 - Add hook to add custom TypoScript templates

See Issue #79140

Description

A new hook in TemplateService allows to add or modify existing TypoScript templates.

Register the hook via $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['Core/TypoScript/TemplateService']['runThroughTemplatesPostProcessing'] in the extensions' ext_localconf.php file.

Example

An example implementation could look like this:

EXT:my_site/ext_localconf.php

$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['Core/TypoScript/TemplateService']['runThroughTemplatesPostProcessing'][1313131313] =
   \MyVendor\MySite\Hooks\TypoScriptHook::class . '->addCustomTypoScriptTemplate';

EXT:my_site/Classes/Hooks/TypoScriptHook.php

namespace MyVendor\MySite\Hooks;

class TypoScriptHook
{

   /**
    * Hooks into TemplateService after
    * @param array $parameters
    * @param \TYPO3\CMS\Core\TypoScript\TemplateService $parentObject
    * @return void
    */
   public function addCustomTypoScriptTemplate($parameters, $parentObject)
   {
      // Disable the inclusion of default TypoScript set via TYPO3_CONF_VARS
      $parameters['isDefaultTypoScriptAdded'] = true;
      // Disable the inclusion of ext_typoscript_setup.txt of all extensions
      $parameters['processExtensionStatics'] = false;

      // No template was found in rootline so far, so a custom "fake" sys_template record is added
      if ($parentObject->outermostRootlineIndexWithTemplate === 0) {
         $row = [
            'uid' => 'my_site_template',
            'config' => '<INCLUDE_TYPOSCRIPT: source="FILE:EXT:my_site/Configuration/TypoScript/site_setup.t3s">',
            'root' => 1,
            'pid' => 0
         ];
         $parentObject->processTemplate($row, 'sys_' . $row['uid'], 0, 'sys_' . $row['uid']);
      }
   }
}