Move ExceptionResponse to proper file.

pymodbus/pdu/__init__.py

@@ -2,11 +2,11 @@
 __all__ = [
     "DecodePDU",
     "ExceptionResponse",
-    "ExceptionResponse",
     "FileRecord",
     "ModbusPDU",
 ]
 
-from pymodbus.pdu.decoders import DecodePDU
-from pymodbus.pdu.file_message import FileRecord
-from pymodbus.pdu.pdu import ExceptionResponse, ModbusPDU
+from .decoders import DecodePDU
+from .exceptionresponse import ExceptionResponse
+from .file_message import FileRecord
+from .pdu import ModbusPDU

pymodbus/pdu/bit_message.py

@@ -6,7 +6,8 @@
 from pymodbus.constants import ModbusStatus
 from pymodbus.datastore import ModbusDeviceContext
 
-from .pdu import ExceptionResponse, ModbusPDU, pack_bitstring, unpack_bitstring
+from .exceptionresponse import ExceptionResponse
+from .pdu import ModbusPDU, pack_bitstring, unpack_bitstring
 
 
 class ReadCoilsRequest(ModbusPDU):

pymodbus/pdu/device.py

@@ -19,9 +19,10 @@
 from collections import OrderedDict
 
 from pymodbus.constants import DeviceInformation
-from pymodbus.pdu.events import ModbusEvent
 from pymodbus.utilities import dict_property
 
+from .events import ModbusEvent
+
 
 # ---------------------------------------------------------------------------#
 #  Modbus Plus Statistics

pymodbus/pdu/diag_message.py

@@ -6,8 +6,8 @@
 
 from pymodbus.constants import ModbusPlusOperation
 from pymodbus.datastore import ModbusDeviceContext
-from pymodbus.pdu.device import ModbusControlBlock
 
+from .device import ModbusControlBlock
 from .pdu import ModbusPDU, pack_bitstring
 
 

pymodbus/pdu/exceptionresponse.py

@@ -0,0 +1,51 @@
+"""Contains exceptionResponse class for modbus."""
+from __future__ import annotations
+
+import struct
+
+from .pdu import ModbusPDU
+
+
+class ExceptionResponse(ModbusPDU):
+    """Base class for a modbus exception PDU."""
+
+    rtu_frame_size = 5
+
+    ILLEGAL_FUNCTION = 0x01
+    ILLEGAL_ADDRESS = 0x02
+    ILLEGAL_VALUE = 0x03
+    DEVICE_FAILURE = 0x04
+    ACKNOWLEDGE = 0x05
+    DEVICE_BUSY = 0x06
+    NEGATIVE_ACKNOWLEDGE = 0x07
+    MEMORY_PARITY_ERROR = 0x08
+    GATEWAY_PATH_UNAVIABLE = 0x0A
+    GATEWAY_NO_RESPONSE = 0x0B
+
+    def __init__(
+            self,
+            function_code: int,
+            exception_code: int = 0,
+            device_id: int = 1,
+            transaction: int = 0) -> None:
+        """Initialize the modbus exception response."""
+        super().__init__(transaction_id=transaction, dev_id=device_id)
+        self.function_code = function_code | 0x80
+        self.exception_code = exception_code
+
+    def __str__(self) -> str:
+        """Build a representation of an exception response."""
+        return (
+            f"{self.__class__.__name__}("
+            f"dev_id={self.dev_id}, "
+            f"function_code={self.function_code}, "
+            f"exception_code={self.exception_code})"
+        )
+
+    def encode(self) -> bytes:
+        """Encode a modbus exception response."""
+        return struct.pack(">B", self.exception_code)
+
+    def decode(self, data: bytes) -> None:
+        """Decode a modbus exception response."""
+        self.exception_code = int(data[0])

pymodbus/pdu/file_message.py

@@ -6,7 +6,8 @@
 
 from pymodbus.datastore import ModbusDeviceContext
 from pymodbus.exceptions import ModbusException
-from pymodbus.pdu.pdu import ModbusPDU
+
+from .pdu import ModbusPDU
 
 
 @dataclass

pymodbus/pdu/mei_message.py

@@ -5,8 +5,10 @@
 
 from pymodbus.constants import DeviceInformation, MoreData
 from pymodbus.datastore import ModbusDeviceContext
-from pymodbus.pdu.device import DeviceInformationFactory, ModbusControlBlock
-from pymodbus.pdu.pdu import ExceptionResponse, ModbusPDU
+
+from .device import DeviceInformationFactory, ModbusControlBlock
+from .exceptionresponse import ExceptionResponse
+from .pdu import ModbusPDU
 
 
 _MCB = ModbusControlBlock()

pymodbus/pdu/other_message.py

@@ -5,8 +5,9 @@
 
 from pymodbus.constants import ModbusStatus
 from pymodbus.datastore import ModbusDeviceContext
-from pymodbus.pdu.device import DeviceInformationFactory, ModbusControlBlock
-from pymodbus.pdu.pdu import ModbusPDU
+
+from .device import DeviceInformationFactory, ModbusControlBlock
+from .pdu import ModbusPDU
 
 
 _MCB = ModbusControlBlock()

pymodbus/pdu/pdu.py

@@ -87,7 +87,9 @@ def decode(self, data: bytes) -> None:
     async def update_datastore(self, context: ModbusDeviceContext) -> ModbusPDU:
         """Run request against a datastore."""
         _ = context
-        return ExceptionResponse(0, 0)
+        raise NotImplementedException(
+            f"update datastore called wrongly {self.__class__.__name__}"
+        )
 
     @classmethod
     def calculateRtuFrameSize(cls, data: bytes) -> int:

pymodbus/pdu/register_message.py

@@ -8,7 +8,9 @@
 
 from pymodbus.datastore import ModbusDeviceContext
 from pymodbus.exceptions import ModbusIOException
-from pymodbus.pdu.pdu import ExceptionResponse, ModbusPDU
+
+from .exceptionresponse import ExceptionResponse
+from .pdu import ModbusPDU
 
 
 class ReadHoldingRegistersRequest(ModbusPDU):

test/pdu/test_pdu.py

@@ -250,7 +250,8 @@ async def test_pdu_default_datastore(self, mock_context):
         """Test that all PDU types can be created."""
         pdu = ModbusPDU()
         context = mock_context()
-        assert await pdu.update_datastore(context)
+        with pytest.raises(NotImplementedException):
+            assert await pdu.update_datastore(context)
 
     @pytest.mark.parametrize(
         ("bytestream", "bitlist"),