Allow `open` with an empty Playlist

[phanan]

Problem

Right now you can't open/initialize the player with a playlist with zero audio resources (empty playlist). The code responsible for this behavior can be seen here:

      if (playable is Playlist && playable.audios.isNotEmpty) {
        playlist = playable;
      } else if (playable is Audio) {
        playlist = Playlist(audios: [playable]);
      }

      if (playlist != null) {
        await _openPlaylist(...)

Basically this means this code won't trigger _openPlaylist():

    AssetsAudioPlayer
      .newPlayer()
      .open(Playlist(audios: []);

This is pretty inconvenient. Imagine having a music app that loads a list of songs from a server and allows the user to tap and queue them one by one. This basic interaction wouldn't be possible without having to check and open the player first:

void addToQueue(Audio song) {
  // since there's no guarantee that the player is already open with a playlist…
  if (_player.playlist == null) {
    _player.open(Playlist(audios: [song]));
  } else {
    _player.playlist!.add(song);
  }
}

Essentially, every interaction with the playlist/player now would need to check and open the player first. I hope you would agree that it would be cumbersome, if not annoying.

Suggestion

To allow open'ing a player with an empty Playlist.

[kizinho]

am facing the issues already when using cached , it cant play the audio even after downloads are completed, you need to rebuild the page to work