Feature: #85828 - Move symfony expression language handling into EXT:core

See Issue #85828

Description

The symfony expression language handling has been moved out of EXT:form into EXT:core. Thus, it is available to be used throughout the core and also for extension developers.

To use the expression language, a provider definition is required which implements the \TYPO3\CMS\Core\ExpressionLanguage\ProviderInterface. The core comes with a \TYPO3\CMS\Core\ExpressionLanguage\DefaultProvider class which can be used directly. For a custom implementation the \TYPO3\CMS\Core\ExpressionLanguage\AbstractProvider class can be extended.

The provider can provide additional variables and expression functions to extend the expression language. For a custom implementation check out the \TYPO3\CMS\Form\Domain\Condition\ConditionProvider class.

An example with the DefaultProvider:

$resolver = GeneralUtility::makeInstance(
   Resolver::class,
   'default',
   [
      'foo' => 1,
      'bar' => 2,
   ]
);
$resolver->evaluate('1 < 2'); // result is true
$resolver->evaluate('foo < bar'); // result is true
$resolver->evaluate('bar < foo'); // result is false

An example with a custom Provider:

First you have to configure a provider, create a file in your extension with the path and name EXT:my_extConfigurationExpressionLanguage.php:

<?php
   return [
      'my-context-identifier' => [
         \TYPO3\CMS\MyExt\ExpressionLanguage\MyCustomProvider::class,
      ]
   ];

Next implement your provider class \TYPO3\CMS\MyExt\ExpressionLanguage\MyCustomProvider::class

class MyCustomProvider extends \TYPO3\CMS\Core\ExpressionLanguage\AbstractProvider
{
   public function __construct()
   {
      $this->expressionLanguageVariables = [
         'foo' => 1,
         'bar' => 2,
      ];
      $this->expressionLanguageProviders = [
         // We use the existing Typo3ConditionsFunctions...
         Typo3ConditionFunctionsProvider::class,
         // ... and our custom function provider
         MyCustomFunctionsProvider::class
      ];
   }
}

Next implement your provider class \TYPO3\CMS\MyExt\ExpressionLanguage\MyCustomFunctionProvider::class

class MyCustomFunctionProvider implements ExpressionFunctionProviderInterface
{
   public function getFunctions()
   {
      return [
         $this->getFooFunction(),
      ];
   }

   protected function getFooFunction(): ExpressionFunction
   {
      return new ExpressionFunction('compatVersion', function ($str) {
         // Not implemented, we only use the evaluator
      }, function ($arguments, $str) {
         return $str === 'foo';
      });
   }
}

And now we use it:

$resolver = GeneralUtility::makeInstance(
   Resolver::class,
   'my-context-identifier',
   [
      'baz' => 3,
   ]
);
$resolver->evaluate('1 < 2'); // result is true
$resolver->evaluate('foo < bar'); // result is true
$resolver->evaluate('bar < baz'); // result is true
$resolver->evaluate('bar < foo'); // result is false
$resolver->evaluate('foo("foo")'); // result is true
$resolver->evaluate('foo("bar")'); // result is false

Impact

The expression language can now be used in other scopes and has no dependency to EXT:form.