Unmanaged file functions replaced with a service

Unmanaged file functions in file.inc have been deprecated and have been moved to the 'file_system' service and \Drupal\Core\File\FileSystemInterface

Methods on the interface now throw FileException or sub-classes if there are errors.

Before:

file_unmanaged_copy($source, $destination, $replace)
file_unmanaged_prepare($source, $destination, $replace)
file_unmanaged_move($source, $destination, $replace)
file_unmanaged_delete($path)
file_unmanaged_delete_recursive($path, $callback)
file_unmanaged_save_data($data, $destination, $replace)
file_prepare_directory($dir)
file_destination($destination, $replace)
file_create_filename($basename, $directory)

After:

<?php

try {
    \Drupal::service('file_system')->copy($source, $destination, $replace);
    \Drupal::service('file_system')->move($source, $destination, $replace);
    \Drupal::service('file_system')->delete($path);
    \Drupal::service('file_system')->deleteRecursive($path, $callback);
    \Drupal::service('file_system')->saveData($data, $destination, $replace);
    \Drupal::service('file_system')->prepareDirectory($directory, $options);
    \Drupal::service('file_system')->getDestinationFilename($destination, $replace);
    \Drupal::service('file_system')->createFilename($basename, $directory);
} 
catch (\Drupal\Core\File\Exception\FileException $e) {
    // Log or set message or doing something else.
}
?>

You can also inject the 'file_system' service into your class as \Drupal\Core\File\FileSystemInterface

In addition the following constants have been deprecated:

FILE_EXISTS_RENAME
FILE_EXISTS_REPLACE
FILE_EXISTS_ERROR

and replaced with

FileSystemInterface::EXISTS_RENAME
FileSystemInterface::EXISTS_REPLACE
FileSystemInterface::EXISTS_ERROR

The destination parameter of the methods FileSystem::copy(), FileSystem::move() and FileSystem::saveData() is now required, this is an API changed compared to 8.7.0-alpha2. 'public://' or file_default_scheme() . '://' can be used as a replacement to get the same behavior but it is discouraged to copy files directly into the top-level directory.