[Storage]: Improvement idea for StorageWrapper to allow calling register with client-creating-closure or separate registerClosure

The issue is about the StorageWrapper class in the Google Cloud PHP library. Look at the StreamWrapper class to understand how client registration works. The proposed changes involve adding a static property for client closures and modifying getClient and unregister methods. Start by examining the existing register method and the stream wrapper registration logic. The goal is to allow lazy initialization of the StorageClient only when a gs:// path is accessed.

Main problem/friction we are having right now is that we have some parts of code that use file accesses via gs://bucketname/path/filename
Due to this in the overall init code for entire application we call

StreamWrapper::register(new StorageClient($config), 'gs');

At the same time we have plenty of API call paths that do not interact with the google storage at all but some flow still may trigger it.
Due to this we are instantiating the client and loading lots of classes without actual need (only 100% confirmed at end of API request).

By adding something like:

  private static $clientClosures = [];

  public static function registerLazyClosure(\Closure $clientClosure, $protocol = null)
  {
    $protocol = $protocol ?: self::DEFAULT_PROTOCOL;
    if (!in_array($protocol, stream_get_wrappers())) {
      if (!stream_wrapper_register($protocol, self::class, STREAM_IS_URL)) {
        throw new \RuntimeException("Failed to register '$protocol://' protocol");
      }
      self::$clientClosures[$protocol] = $clientClosure;
      return true;
    }
    return false;
  }

and changing getClient and unregister to:

  public static function getClient($protocol = null)
  {
    $protocol = $protocol ?: self::DEFAULT_PROTOCOL;
    if (isset(self::$clientClosures[$protocol])) {
      self::$clients[$protocol] = self::$clientClosures[$protocol]();
      unset(self::$clientClosures[$protocol]);
    }
    return self::$clients[$protocol];
  }

  public static function unregister($protocol = null)
  {
    $protocol = $protocol ?: self::DEFAULT_PROTOCOL;
    stream_wrapper_unregister($protocol);
    unset(self::$clients[$protocol], self::$clientClosures[$protocol]);
  }

it would be possible to register a closure that will be executed only when any gs://bucketname/path/filename path is actually accessed and not before.

This became evident when using profiler mode in our deployment for simple ping/pong API endpoint and tracking what parts of code consume unneeded overhead.

In PHP 8.4+ it will be possible to use lazy ghost or proxy objects, but we are still stuck at 8.3 for a while.

Currently we implemented custom-made stream wrapper to achieve that closure-creation approach but possibly would be better to have it natively in the storage library.