StatefulDecoder.push() should return None when given b"" (disconnect)

README.md

@@ -46,6 +46,10 @@ _send(irctokens.format("NICK", ["nickname"]))
 
 while True:
     lines = d.push(s.recv(1024))
+    if lines == None:
+        print("! disconnected")
+        break
+
     for line in lines:
         if line.command == "PING":
             to_send = irctokens.format("PONG", [line.params[0]])

irctokens/stateful.py

@@ -6,7 +6,10 @@ class StatefulDecoder(object):
         self._fallback = fallback
         self._buffer = b""
 
-    def push(self, data: bytes) -> typing.List[Line]:
+    def push(self, data: bytes) -> typing.Optional[typing.List[Line]]:
+        if not data:
+            return None
+
         self._buffer += data
         lines = [l.strip(b"\r") for l in self._buffer.split(b"\n")]
         self._buffer = lines.pop(-1)

test/stateful_decode.py

@@ -31,3 +31,15 @@ class TestFallback(unittest.TestCase):
         self.assertEqual(len(lines), 1)
         line = irctokens.tokenise("PRIVMSG #channel hélló")
         self.assertEqual(lines[0], line)
+
+class TestEmpty(unittest.TestCase):
+    def test_immediate(self):
+        d = irctokens.StatefulDecoder()
+        lines = d.push(b"")
+        self.assertIsNone(lines)
+
+    def test_buffer_unfinished(self):
+        d = irctokens.StatefulDecoder()
+        d.push(b"PRIVMSG #channel hello")
+        lines = d.push(b"")
+        self.assertIsNone(lines)