Fixed #1013: Empty mention should be None instead of empty string.

CHANGES/1013.bugfix.rst

@@ -0,0 +1 @@
+Fixed empty mention in command parsing, now it will be None instead of an empty string

aiogram/filters/command.py

@@ -132,7 +132,10 @@ class Command(Filter):
         # "/command@mention" -> "/", ("command", "@", "mention")
         prefix, (command, _, mention) = full_command[0], full_command[1:].partition("@")
         return CommandObject(
-            prefix=prefix, command=command, mention=mention, args=args[0] if args else None
+            prefix=prefix,
+            command=command,
+            mention=mention or None,
+            args=args[0] if args else None,
         )
 
     def validate_prefix(self, command: CommandObject) -> None:

tests/test_filters/test_command.py

@@ -104,6 +104,23 @@ class TestCommandFilter:
         assert "args" in result
         assert result["args"] == "42"
 
+    async def test_empty_mention_is_none(self, bot: MockedBot):
+        # Fixed https://github.com/aiogram/aiogram/issues/1013:
+        #   Empty mention should be None instead of empty string.
+
+        message = Message(
+            message_id=0,
+            text="/test",
+            chat=Chat(id=42, type="private"),
+            date=datetime.datetime.now(),
+        )
+        command = Command("test")
+        result = await command(message=message, bot=bot)
+
+        assert "command" in result
+        command_obj: CommandObject = result["command"]
+        assert command_obj.mention is None
+
 
 class TestCommandObject:
     @pytest.mark.parametrize(