TYPO3 Core

We want to add custom properties to a \TYPO3\CMS\Core\Resource\File. However, as these properties may not exist, a warning is thrown.

PHP Warning: Undefined array key "alternative" in typo3/sysext/core/Classes/Resource/File.php line 184

The problematic code:

foreach ($properties as $key => $value) {
  if ($this->properties[$key] !== $value) {
    if (!in_array($key, $this->updatedProperties)) {
      $this->updatedProperties[] = $key;
    }
    $this->properties[$key] = $value;
  }
}

The simplest fix might be to change

$this->properties[$key] !== $value

$this->properties[$key] ?? null !== $value

or replace the whole code with something like this (untested):

        $this->updatedProperties = array_merge($this->updatedProperties, array_keys(array_diff_assoc($this->properties, $properties)));
        $this->properties = array_merge($this->properties, $properties);