Specific Exceptions: Adapting socketcan interface

can/exceptions.py

@@ -85,6 +85,7 @@ class CanOperationError(CanError):
       - The driver rejected a message that was meant to be sent
       - Cyclic redundancy check (CRC) failed
       - A message remained unacknowledged
+      - A buffer is full
     """
 
 

can/interfaces/socketcan/socketcan.py

@@ -278,24 +278,19 @@ def send_bcm(bcm_socket: socket.socket, data: bytes) -> int:
     """
     try:
         return bcm_socket.send(data)
-    except OSError as e:
-        base = "Couldn't send CAN BCM frame. OS Error {}: {}\n".format(
-            e.errno, e.strerror
-        )
-
-        if e.errno == errno.EINVAL:
-            raise can.CanError(
-                base + "You are probably referring to a non-existing frame."
-            )
-
-        elif e.errno == errno.ENETDOWN:
-            raise can.CanError(base + "The CAN interface appears to be down.")
-
-        elif e.errno == errno.EBADF:
-            raise can.CanError(base + "The CAN socket appears to be closed.")
-
+    except OSError as error:
+        base = f"Couldn't send CAN BCM frame due to OS Error: {error.strerror}"
+
+        if error.errno == errno.EINVAL:
+            specific_message = " You are probably referring to a non-existing frame."
+        elif error.errno == errno.ENETDOWN:
+            specific_message = " The CAN interface appears to be down."
+        elif error.errno == errno.EBADF:
+            specific_message = " The CAN socket appears to be closed."
         else:
-            raise e
+            specific_message = ""
+
+        raise can.CanOperationError(base + specific_message, error.errno) from error
 
 
 def _compose_arbitration_id(message: Message) -> int:
@@ -330,7 +325,7 @@ def __init__(
         messages: Union[Sequence[Message], Message],
         period: float,
         duration: Optional[float] = None,
-    ):
+    ) -> None:
         """Construct and :meth:`~start` a task.
 
         :param bcm_socket: An open BCM socket on the desired CAN channel.
@@ -378,7 +373,7 @@ def _tx_setup(self, messages: Sequence[Message]) -> None:
         log.debug("Sending BCM command")
         send_bcm(self.bcm_socket, header + body)
 
-    def _check_bcm_task(self):
+    def _check_bcm_task(self) -> None:
         # Do a TX_READ on a task ID, and check if we get EINVAL. If so,
         # then we are referring to a CAN message with the existing ID
         check_header = build_bcm_header(
@@ -394,14 +389,13 @@ def _check_bcm_task(self):
         )
         try:
             self.bcm_socket.send(check_header)
-        except OSError as e:
-            if e.errno != errno.EINVAL:
-                raise e
+        except OSError as error:
+            if error.errno != errno.EINVAL:
+                raise can.CanOperationError("failed to check", error.errno) from error
         else:
-            raise ValueError(
-                "A periodic task for Task ID {} is already in progress by SocketCAN Linux layer".format(
-                    self.task_id
-                )
+            raise can.CanOperationError(
+                f"A periodic task for task ID {self.task_id} is already in progress "
+                "by the SocketCAN Linux layer"
             )
 
     def stop(self) -> None:
@@ -537,7 +531,7 @@ def capture_message(
         else:
             channel = None
     except socket.error as error:
-        raise can.CanError(f"Error receiving: {error}")
+        raise can.CanOperationError(f"Error receiving: {error.strerror}", error.errno)
 
     can_id, can_dlc, flags, data = dissect_can_frame(cf)
 
@@ -550,7 +544,7 @@ def capture_message(
     # see https://man7.org/linux/man-pages/man3/timespec.3.html -> struct timespec for details
     seconds, nanoseconds = RECEIVED_TIMESTAMP_STRUCT.unpack_from(cmsg_data)
     if nanoseconds >= 1e9:
-        raise can.CanError(
+        raise can.CanOperationError(
             f"Timestamp nanoseconds field was out of range: {nanoseconds} not less than 1e9"
         )
     timestamp = seconds + nanoseconds * 1e-9
@@ -716,9 +710,11 @@ def _recv_internal(
             # get all sockets that are ready (can be a list with a single value
             # being self.socket or an empty list if self.socket is not ready)
             ready_receive_sockets, _, _ = select.select([self.socket], [], [], timeout)
-        except socket.error as exc:
+        except socket.error as error:
             # something bad happened (e.g. the interface went down)
-            raise can.CanError(f"Failed to receive: {exc}")
+            raise can.CanOperationError(
+                f"Failed to receive: {error.strerror}", error.errno
+            )
 
         if ready_receive_sockets:  # not empty
             get_channel = self.channel == ""
@@ -767,7 +763,7 @@ def send(self, msg: Message, timeout: Optional[float] = None) -> None:
             data = data[sent:]
             time_left = timeout - (time.time() - started)
 
-        raise can.CanError("Transmit buffer full")
+        raise can.CanOperationError("Transmit buffer full")
 
     def _send_once(self, data: bytes, channel: Optional[str] = None) -> int:
         try:
@@ -776,8 +772,10 @@ def _send_once(self, data: bytes, channel: Optional[str] = None) -> int:
                 sent = self.socket.sendto(data, (channel,))
             else:
                 sent = self.socket.send(data)
-        except socket.error as exc:
-            raise can.CanError("Failed to transmit: %s" % exc)
+        except socket.error as error:
+            raise can.CanOperationError(
+                f"Failed to transmit: {error.strerror}", error.errno
+            )
         return sent
 
     def _send_periodic_internal(

test/logformats_test.py

@@ -316,7 +316,7 @@ def test_append_mode(self):
             try:
                 writer = self.writer_constructor(self.test_file_name)
             except TypeError:
-                # is the is still a problem, raise the initial error
+                # if it is still a problem, raise the initial error
                 raise e
         with writer:
             for message in second_part:

test/test_cyclic_socketcan.py

@@ -255,10 +255,10 @@ def test_start_already_started_task(self):
         time.sleep(0.1)
 
         # Try to start it again, task_id is not incremented in this case
-        with self.assertRaises(ValueError) as ctx:
+        with self.assertRaises(can.CanOperationError) as ctx:
             task_a.start()
         self.assertEqual(
-            "A periodic task for Task ID 1 is already in progress by SocketCAN Linux layer",
+            "A periodic task for task ID 1 is already in progress by the SocketCAN Linux layer",
             str(ctx.exception),
         )