[GTK] Fix unable to prefetch magnet in thinclient

A UnicodeDecodeError is raised in transfer module when attempting to
prefetch a magnet.

This is result of passing a Python dict containing text bytes and raw
bytes that cannot be decoded as utf-8 in rencode when recieving the
message. This could be handled in rencode by returning raw bytes if
decoding fails (perhaps with a strict mode?) however better to follow
convention of encoding raw bytes in base64 in API calls.

Fixed by retaining bencoding and encoding with base64 when sending
result.

Resolves: https://github.com/deluge-torrent/deluge/pull/334

deluge/core/core.py

@@ -432,12 +432,14 @@ class Core(component.Component):
 
         Used by UIs to get magnet files for selection before adding to session.
 
+        The metadata is bencoded and for transfer base64 encoded.
+
         Args:
             magnet (str): The magnet URI.
             timeout (int): Number of seconds to wait before canceling request.
 
         Returns:
-            Deferred: A tuple of (torrent_id (str), metadata (dict)) for the magnet.
+            Deferred: A tuple of (torrent_id (str), metadata (str)) for the magnet.
 
         """
 

deluge/core/torrentmanager.py

@@ -13,6 +13,7 @@ import operator
 import os
 import pickle
 import time
+from base64 import b64encode
 from collections import namedtuple
 from tempfile import gettempdir
 
@@ -396,12 +397,12 @@ class TorrentManager(component.Component):
         else:
             self.session.remove_torrent(torrent_handle, 1)
 
-        metadata = None
+        metadata = b''
         if isinstance(torrent_info, lt.torrent_info):
             log.debug('prefetch metadata received')
-            metadata = lt.bdecode(torrent_info.metadata())
+            metadata = torrent_info.metadata()
 
-        return torrent_id, metadata
+        return torrent_id, b64encode(metadata)
 
     def _build_torrent_options(self, options):
         """Load default options and update if needed."""

deluge/tests/test_core.py

@@ -317,7 +317,7 @@ class CoreTestCase(BaseTestCase):
     def test_prefetch_metadata_existing(self):
         """Check another call with same magnet returns existing deferred."""
         magnet = 'magnet:?xt=urn:btih:ab570cdd5a17ea1b61e970bb72047de141bce173'
-        expected = ('ab570cdd5a17ea1b61e970bb72047de141bce173', None)
+        expected = ('ab570cdd5a17ea1b61e970bb72047de141bce173', b'')
 
         def on_result(result):
             self.assertEqual(result, expected)

deluge/tests/test_torrentmanager.py

@@ -15,6 +15,7 @@ from twisted.internet import defer, task
 from twisted.trial import unittest
 
 from deluge import component
+from deluge.bencode import bencode
 from deluge.common import windows_check
 from deluge.core.core import Core
 from deluge.core.rpcserver import RPCServer
@@ -82,6 +83,8 @@ class TorrentmanagerTestCase(BaseTestCase):
 
         expected = (
             'ab570cdd5a17ea1b61e970bb72047de141bce173',
+            b64encode(
+                bencode(
                     {
                         b'piece length': 32768,
                         b'sha1': (
@@ -109,7 +112,9 @@ class TorrentmanagerTestCase(BaseTestCase):
                         b'length': 307949,
                         b'name.utf-8': b'azcvsupdater_2.6.2.jar',
                         b'ed2k': b'>p\xefl\xfa]\x95K\x1b^\xc2\\;;e\xb7',
-            },
+                    }
+                )
+            ),
         )
         self.assertEqual(expected, self.successResultOf(d))
 
@@ -117,7 +122,7 @@ class TorrentmanagerTestCase(BaseTestCase):
         magnet = 'magnet:?xt=urn:btih:ab570cdd5a17ea1b61e970bb72047de141bce173'
         d = self.tm.prefetch_metadata(magnet, 30)
         self.clock.advance(30)
-        expected = ('ab570cdd5a17ea1b61e970bb72047de141bce173', None)
+        expected = ('ab570cdd5a17ea1b61e970bb72047de141bce173', b'')
         return d.addCallback(self.assertEqual, expected)
 
     @pytest.mark.todo

deluge/ui/gtk3/addtorrentdialog.py

@@ -8,7 +8,7 @@
 
 import logging
 import os
-from base64 import b64encode
+from base64 import b64decode, b64encode
 from xml.sax.saxutils import escape as xml_escape
 from xml.sax.saxutils import unescape as xml_unescape
 
@@ -16,6 +16,7 @@ from gi.repository import Gtk
 from gi.repository.GObject import TYPE_INT64, TYPE_UINT64
 
 import deluge.component as component
+from deluge.bencode import bdecode
 from deluge.common import (
     create_magnet_uri,
     decode_bytes,
@@ -268,6 +269,7 @@ class AddTorrentDialog(component.Component):
             return
 
         if metadata:
+            metadata = bdecode(b64decode(metadata))
             info = TorrentInfo.from_metadata(metadata, [[t] for t in trackers])
             self.files[info_hash] = info.files
             self.infos[info_hash] = info.filedata