error handling w/ duplicate torrents

[madd512]

var WebTorrent = require('webtorrent-hybrid');

var client = new WebTorrent();

client.seed('./www', torrent => {
  console.log('seed worked');
  try {
    client.add(torrent.infoHash, () => console.log('add worked'))
  } catch (err) {
    console.error('got error', err)
  }
})

Expected output:

$ node test.js 
seed worked
add worked

Or, less preferably:

$ node test.js 
seed worked
got error [Error: There is already a swarm with info hash 55f65714bb41dcdf19fd3ccceb89fdfded970de2 listening on port 48839]

Actual output:

$ node test.js 
seed worked
events.js:85
      throw er; // Unhandled 'error' event
            ^
Error: There is already a swarm with info hash ... listening on port 48839
    at /.../node_modules/webtorrent-hybrid/node_modules/webtorrent/node_modules/bittorrent-swarm/lib/tcp-pool.js:101:22
    at process._tickCallback (node.js:355:11)

Might it be worth adding an err argument to the callbacks, or just returning an existing torrent when it's already been added/seeded?

[feross]

You don't need to manually add the torrent to the client when you're seeding - it's handled for you. client.seed actually calls client.add internally :-)

Can't add an err argument to the callback because it's actually just a shorthand for listening to the 'torrent' event. Events don't have err arguments.

I like the idea of returning the existing torrent instead of failing with an error. Let's do that.

[madd512]

I like the idea of returning the existing torrent instead of failing with an error. Let's do that.

I was hoping you'd say that :)

I'm looking through the code. The error is thrown here, in bittorrent-swarm. I believe it can be caught and handled here.

I could intercept this error and emit the torrent event again, but that may cause unexpected behavior for anybody expecting that event to be emitted once per torrent, and that would sort of leak behavior out in a weird way which I don't like.

Instead, I think I'll iterate through self.torrents, running clientOnTorrent on each one, assuming ontorrent is has been defined. Since clientOnTorrent only runs ontorrent when the infoHash matches, I think that should do it... maybe...

[madd512]

PR here #351

[feross]

Released as 0.49.0.