feat: Download.bittorrent returns None if no "bittorrent" key pre…

…sent

BREAKING CHANGE: this could be a breaking change if your code does not
check if `download.bittorrent` is an instance of `BitTorrent`
before accessing its attributes.

Reference: issue #53.

src/aria2p/downloads.py

@@ -638,7 +638,7 @@ def bittorrent(self):
 
         BitTorrent only.
         """
-        if not self._bittorrent:
+        if not self._bittorrent and "bittorrent" in self._struct:
             self._bittorrent = BitTorrent(self._struct.get("bittorrent"))
         return self._bittorrent
 

tests/test_downloads.py

@@ -119,6 +119,11 @@ def test_bittorrent(self):
         self.download._struct["bittorrent"] = {"mode": "single"}
         assert self.download.bittorrent.mode is None
 
+        # assert is None when "bittorrent" key is not in struct
+        del self.download._struct["bittorrent"]
+        self.download._bittorrent = None
+        assert self.download.bittorrent is None
+
     def test_completed_length(self):
         assert self.download.completed_length == 889_592_532