On duplicate torrent add, don't emit 'infoHash'

Private 'infoHash' event allows client.add to check for duplicate
torrents and destroy them before the normal 'infoHash' event is
emitted. Prevents user applications from needing to deal with duplicate
'infoHash' events.

CHANGELOG.md

@@ -1,5 +1,9 @@
 # WebTorrent Version History
 
+## UNRELEASED
+
+- When a duplicate torrent is added, don't emit the 'infoHash' event after 'error'. The 'error' event should be the last event.
+
 ## v0.93.1 - 2016-05-08
 
 - Remove `path-exists` dependency.

index.js

@@ -240,7 +240,7 @@ WebTorrent.prototype.add = function (torrentId, opts, ontorrent) {
   var torrent = new Torrent(torrentId, self, opts)
   self.torrents.push(torrent)
 
-  torrent.once('infoHash', onInfoHash)
+  torrent.once('_infoHash', onInfoHash)
   torrent.once('ready', onReady)
   torrent.once('close', onClose)
 
@@ -262,7 +262,7 @@ WebTorrent.prototype.add = function (torrentId, opts, ontorrent) {
   }
 
   function onClose () {
-    torrent.removeListener('infoHash', onInfoHash)
+    torrent.removeListener('_infoHash', onInfoHash)
     torrent.removeListener('ready', onReady)
     torrent.removeListener('close', onClose)
   }

lib/torrent.js

@@ -253,8 +253,14 @@ Torrent.prototype._onParsedTorrent = function (parsedTorrent) {
   }, RECHOKE_INTERVAL)
   if (self._rechokeIntervalId.unref) self._rechokeIntervalId.unref()
 
+  // Private 'infoHash' event allows client.add to check for duplicate torrents and
+  // destroy them before the normal 'infoHash' event is emitted. Prevents user
+  // applications from needing to deal with duplicate 'infoHash' events.
+  self.emit('_infoHash', self.infoHash)
+  if (self.destroyed) return
+
   self.emit('infoHash', self.infoHash)
-  if (self.destroyed) return // user might destroy torrent in `infoHash` event handler
+  if (self.destroyed) return // user might destroy torrent in event handler
 
   if (self.client.listening) {
     self._onListening()