Add __del__ method to BusABC

can/bus.py

@@ -44,12 +44,14 @@ class BusABC(metaclass=ABCMeta):
     #: Log level for received messages
     RECV_LOGGING_LEVEL = 9
 
+    _is_shutdown: bool = False
+
     @abstractmethod
     def __init__(
         self,
         channel: Any,
         can_filters: Optional[can.typechecking.CanFilters] = None,
-        **kwargs: object
+        **kwargs: object,
     ):
         """Construct and open a CAN bus instance of the specified type.
 
@@ -417,17 +419,34 @@ def flush_tx_buffer(self) -> None:
 
     def shutdown(self) -> None:
         """
-        Called to carry out any interface specific cleanup required
-        in shutting down a bus.
+        Called to carry out any interface specific cleanup required in shutting down a bus.
+
+        This method can be safely called multiple times.
         """
+        if self._is_shutdown:
+            LOG.debug("%s is already shut down", self.__class__)
+            return
+
         self.stop_all_periodic_tasks()
+        self._is_shutdown = True
 
     def __enter__(self):
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.shutdown()
 
+    def __del__(self) -> None:
+        try:
+            if not self._is_shutdown:
+                # We do some best-effort cleanup if the user
+                # forgot to properly close the bus instance
+                self.shutdown()
+                LOG.warning("%s was not properly shut down", self.__class__)
+        except Exception as e:  # pylint: disable=W0703
+            # Prevent unwanted output from being printed to stdout/stderr
+            LOG.debug(e)
+
     @property
     def state(self) -> BusState:
         """

can/interfaces/ixxat/canlib.py

@@ -147,6 +147,7 @@ def _send_periodic_internal(self, msgs, period, duration=None):
         return self.bus._send_periodic_internal(msgs, period, duration)
 
     def shutdown(self):
+        super().shutdown()
         return self.bus.shutdown()
 
     @property

can/interfaces/socketcand/socketcand.py

@@ -170,5 +170,5 @@ def send(self, msg, timeout=None):
         self._tcp_send(ascii_msg)
 
     def shutdown(self):
-        self.stop_all_periodic_tasks()
+        super().shutdown()
         self.__socket.close()

test/test_bus.py

@@ -1,3 +1,4 @@
+import gc
 from unittest.mock import patch
 
 import can
@@ -12,3 +13,11 @@ def test_bus_ignore_config():
 
         _ = can.Bus(interface="virtual")
         assert can.util.load_config.called
+
+
+@patch.object(can.bus.BusABC, "shutdown")
+def test_bus_attempts_self_cleanup(mock_shutdown):
+    bus = can.Bus(interface="virtual")
+    del bus
+    gc.collect()
+    mock_shutdown.assert_called()

test/test_interface.py

@@ -0,0 +1,36 @@
+import importlib
+from unittest.mock import patch
+
+import pytest
+
+import can
+from can.interfaces import BACKENDS
+
+
+@pytest.fixture(params=(BACKENDS.keys()))
+def constructor(request):
+    mod, cls = BACKENDS[request.param]
+
+    try:
+        module = importlib.import_module(mod)
+        constructor = getattr(module, cls)
+    except:
+        pytest.skip("Unable to load interface")
+
+    return constructor
+
+
+@pytest.fixture
+def interface(constructor):
+    with patch.object(constructor, "__init__", return_value=None):
+        return constructor()
+
+
+@patch.object(can.bus.BusABC, "shutdown")
+def test_all_interfaces_call_parent_shutdown(mock_shutdown, interface):
+    try:
+        interface.shutdown()
+    except:
+        pass
+    finally:
+        mock_shutdown.assert_called()