TemplateDirIterator example

    public function collectDir(string $dir, string $ext = '.twig'): array
    {
        $iterator = new \RegexIterator(
            new \RecursiveIteratorIterator(
                new \RecursiveDirectoryIterator($dir), \RecursiveIteratorIterator::LEAVES_ONLY
            ), '{'.preg_quote($ext).'$}'
        );

        return $this->collect(new TemplateDirIterator($iterator));
    }

    /** * Returns deprecations for passed templates. * * @param \Traversable $iterator An iterator of templates (where keys are template names and values the contents of the template) * * @return array An array of deprecations */
    public function collect(\Traversable $iterator): array
    {
        

// Rename hooks.     $theme_file = "$tmp_dir/$destination_theme.theme";
    if (file_exists($theme_file)) {
      if (!file_put_contents($theme_file, preg_replace("/(function )($source_theme_name)(_.*)/", "$1$destination_theme$3", file_get_contents($theme_file)))) {
        $io->getErrorStyle()->error("The theme file $theme_file could not be written.");
        return 1;
      }
    }

    // Rename references to libraries in templates.     $iterator = new TemplateDirIterator(new \RegexIterator(
      new \RecursiveIteratorIterator(
        new \RecursiveDirectoryIterator($tmp_dir), \RecursiveIteratorIterator::LEAVES_ONLY
      ), '/' . preg_quote('.html.twig') . '$/'
    ));

    foreach ($iterator as $template_file => $contents) {
      $new_template_content = preg_replace("/(attach_library\(['\")])$source_theme_name(\/.*['\"]\))/", "$1$destination_theme$2", $contents);
      if (!file_put_contents($template_file, $new_template_content)) {
        $io->getErrorStyle()->error("The template file $template_file could not be written.");
        return 1;
      }
    }