fix(connection): prevent IndexError on malformed ChibiOS banner line

_extract_chibios_version_from_banner crashed with IndexError when a
banner line starting with "ChibiOS:" did not contain a space followed
by a version hash (for example a truncated "ChibiOS:" line, or
"ChibiOS:hash" without the expected space separator).

msg.split(" ")[1] unconditionally indexed the second element of the
split, which does not exist when the separator is absent. The
IndexError propagated out of the banner-parsing loop during flight
controller connection setup and aborted the whole connection attempt.

Use split(" ", 1) and guard the length before indexing, falling back
to an empty version string. The surrounding code already handles an
empty os_custom_version correctly (it logs a version mismatch warning
against info.os_custom_version when the two differ).

Add two unit tests covering the malformed banner cases that previously
raised IndexError.

Signed-off-by: Yash Goel <yashvardhan664@gmail.com>

Author: yashhzd

ardupilot_methodic_configurator/backend_flightcontroller_connection.py

@@ -631,7 +631,8 @@ def _extract_chibios_version_from_banner(self, banner_msgs: list[str]) -> tuple[
 
         for i, msg in enumerate(banner_msgs):
             if "ChibiOS:" in msg:
-                os_custom_version = msg.split(" ")[1].strip()
+                parts = msg.split(" ", 1)
+                os_custom_version = parts[1].strip() if len(parts) > 1 else ""
                 hash_len1 = max(7, len(os_custom_version) - 1)
                 hash_len2 = max(7, len(self.info.os_custom_version) - 1)
                 hash_len = min(hash_len1, hash_len2)

tests/test_backend_flightcontroller_connection.py

@@ -1518,6 +1518,41 @@ def test_extract_chibios_version_returns_none_index_when_absent(self) -> None:
         assert os_ver == ""
         assert index is None
 
+    def test_extract_chibios_version_handles_banner_without_trailing_space(self) -> None:
+        """
+        _extract_chibios_version_from_banner tolerates a malformed banner line with no space after the prefix.
+
+        GIVEN: Banner messages where the ChibiOS line has no space between the prefix and the version
+        WHEN: _extract_chibios_version_from_banner is called
+        THEN: An empty version string should be returned
+        AND: The index of the ChibiOS line should still be recorded
+        AND: No IndexError should be raised
+        """
+        connection = FlightControllerConnection(info=FlightControllerInfo())
+        banner_msgs = ["ArduCopter V4.5.0", "ChibiOS:"]
+
+        os_ver, index = connection._extract_chibios_version_from_banner(banner_msgs)
+
+        assert os_ver == ""
+        assert index == 1
+
+    def test_extract_chibios_version_handles_banner_with_only_prefix(self) -> None:
+        """
+        _extract_chibios_version_from_banner tolerates a banner line that is exactly the ChibiOS prefix.
+
+        GIVEN: A banner line consisting only of the 'ChibiOS:' prefix with no hash at all
+        WHEN: _extract_chibios_version_from_banner is called
+        THEN: An empty version string should be returned
+        AND: No IndexError should be raised
+        """
+        connection = FlightControllerConnection(info=FlightControllerInfo())
+        banner_msgs = ["ChibiOS:"]
+
+        os_ver, index = connection._extract_chibios_version_from_banner(banner_msgs)
+
+        assert os_ver == ""
+        assert index == 0
+
     def test_extract_firmware_type_from_message_after_chibios(self) -> None:
         """
         _extract_firmware_type_from_banner extracts type from message after ChibiOS line.