raise ValueError when trying to tokenise without a command

irctokens/line.py

@@ -85,6 +85,8 @@ def _tokenise(
     if params[0][0] == ":":
         source = params.pop(0)[1:]
 
+    if not params:
+        raise ValueError("Cannot tokenise command-less line")
     command = params.pop(0).upper()
 
     if trailing_sep:

test/tokenise.py

@@ -76,3 +76,13 @@ class TokenTestNul(unittest.TestCase):
         line = irctokens.tokenise(
             ":nick!user@host PRIVMSG #channel :hello\x00 world")
         self.assertEqual(line.params, ["#channel", "hello"])
+
+class TokenTestNoCommand(unittest.TestCase):
+    def test(self):
+        def _test1():
+            line = irctokens.tokenise(":n!u@h")
+        def _test2():
+            line = irctokens.tokenise("@tag=1 :n!u@h")
+
+        self.assertRaises(ValueError, _test1)
+        self.assertRaises(ValueError, _test2)