Repository: symfony/symfony
File: src/Symfony/Component/Filesystem/Filesystem.php (PHP)

Code before:
        }
        $targetDir = rtrim($targetDir, '/\\');
        $originDir = rtrim($originDir, '/\\');
        $originDirLen = \strlen($originDir);

        if (!$this->exists($originDir)) {
            throw new IOException(sprintf('The origin directory specified "%s" was not found.', $originDir), 0, null, $originDir);
        }

        // Iterate in destination folder to remove obsolete entries
        if ($this->exists($targetDir) && isset($options['delete']) && $options['delete']) {
            $deleteIterator = $iterator;
            if (null === $deleteIterator) {
                $flags = \FilesystemIterator::SKIP_DOTS;
                $deleteIterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($targetDir, $flags), \RecursiveIteratorIterator::CHILD_FIRST);
            }
            $targetDirLen = \strlen($targetDir);
            foreach ($deleteIterator as $file) {
                $origin = $originDir.substr($file->getPathname(), $targetDirLen);
                if (!$this->exists($origin)) {
                    $this->remove($file);
                }
            }
        }

        $followSymlinks = isset($options['follow_symlinks']) && $options['follow_symlinks'] || isset($options['copy_on_windows']) && $options['copy_on_windows'];

        if (null === $iterator) {
            $flags = $followSymlinks ? \FilesystemIterator::SKIP_DOTS | \FilesystemIterator::FOLLOW_SYMLINKS : \FilesystemIterator::SKIP_DOTS;
            $iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($originDir, $flags), \RecursiveIteratorIterator::SELF_FIRST);
        }

        $this->mkdir($targetDir);
        $filesCreatedWhileMirroring = [];

        foreach ($iterator as $file) {
            if ($file->getPathname() === $targetDir || $file->getRealPath() === $targetDir || isset($filesCreatedWhileMirroring[$file->getRealPath()])) {
                continue;
            }

            $target = $targetDir.substr($file->getPathname(), $originDirLen);
            $filesCreatedWhileMirroring[$target] = true;

            if (!$followSymlinks && is_link($file)) {
                $this->symlink($file->getLinkTarget(), $target);
            } elseif (is_dir($file)) {
                $this->mkdir($target);
            } elseif (is_file($file)) {
                $this->copy($file, $target, $options['override'] ?? false);
            } else {
                throw new IOException(sprintf('Unable to guess "%s" file type.', $file), 0, null, $file);

Review comment (suggestion):
This is working fine, but I'm personally prefer group condition options with parentheses for readability
E.g. 
`(isset($options['follow_symlinks']) && $options['follow_symlinks']) || (isset($options['copy_on_windows']) && $options['copy_on_windows']);`

But this is not mandatory to change

Code after:
     *                                    - $options['delete'] Whether to delete files that are not in the source directory (defaults to false)
     *
     * @throws IOException When file type is unknown
     */
    public function mirror(string $originDir, string $targetDir, ?\Traversable $iterator = null, array $options = []): void
    {
        if (isset($options['copy_on_windows'])) {
            trigger_deprecation('symfony/filesystem', '8.1', 'Calling "%s()" with option "copy_on_windows" is deprecated, use "follow_symlinks" option instead.', __METHOD__);
        }

        $targetDir = rtrim($targetDir, '/\\');
        $originDir = rtrim($originDir, '/\\');
        $originDirLen = \strlen($originDir);

        if (!$this->exists($originDir)) {
            throw new IOException(\sprintf('The origin directory specified "%s" was not found.', $originDir), 0, null, $originDir);
        }

        // Iterate in destination folder to remove obsolete entries
        if ($this->exists($targetDir) && isset($options['delete']) && $options['delete']) {
            $deleteIterator = $iterator;
            if (null === $deleteIterator) {
                $flags = \FilesystemIterator::SKIP_DOTS;
                $deleteIterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($targetDir, $flags), \RecursiveIteratorIterator::CHILD_FIRST);
            }
            $targetDirLen = \strlen($targetDir);
            foreach ($deleteIterator as $file) {
                $origin = $originDir.substr($file->getPathname(), $targetDirLen);
                if (!$this->exists($origin)) {
                    $this->remove($file);
                }
            }
        }

        $followSymlinks = $options['follow_symlinks'] ?? $options['copy_on_windows'] ?? false;

        if (null === $iterator) {
            $flags = $followSymlinks ? \FilesystemIterator::SKIP_DOTS | \FilesystemIterator::FOLLOW_SYMLINKS : \FilesystemIterator::SKIP_DOTS;
            $iterator = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($originDir, $flags), \RecursiveIteratorIterator::SELF_FIRST);
        }

        $this->mkdir($targetDir);
        $filesCreatedWhileMirroring = [];

        foreach ($iterator as $file) {
            if ($file->getPathname() === $targetDir || $file->getRealPath() === $targetDir || isset($filesCreatedWhileMirroring[$file->getRealPath()])) {
                continue;
            }

            $target = $targetDir.substr($file->getPathname(), $originDirLen);
            $filesCreatedWhileMirroring[$target] = true;