style fixes

Author: lud4ik

lud4ik/tests/test_command.py

@@ -62,6 +62,11 @@ def test_ackfinish(self):
         self.assertIsInstance(Packet.unpack(packet.pack()[self.LENGTH:]),
                               AckFinish)
 
+    def test_without_fields(self):
+        with self.assertRaises(FieldDeclarationError):
+            class ErrorClass(Packet):
+                pass
+
     def test_without_cmd(self):
         with self.assertRaises(FieldDeclarationError):
             class ErrorClass(Packet):

lud4ik/work/protocol.py

@@ -24,10 +24,8 @@ def __init__(self, name, bases, dct):
             if isinstance(value, Field):
                 value.name = attr
                 self.fields[attr] = value
-        try:
-            if not isinstance(next(iter(self.fields.values())), Cmd):
-                raise FieldDeclarationError('Command shoud be first field.')
-        except StopIteration:
+
+        if not (self.fields and isinstance(next(iter(self.fields.values())), Cmd)):
             raise FieldDeclarationError('Command shoud be first field.')
 
         self.__class__.packets[cmd.id] = self