fix(pdo): avoid PdoMaps(0,0) aliasing; delegate combined PDO to rx/tx

- Add PdoMaps map_offset/com_offset and __getitem__ fallbacks for record indices
- Replace dict merge with _CombinedPdoMaps; route 0x1400-0x17FF/0x1800-0x1BFF in PDO
- Expand PdoBase fast path to 0x1400-0x1BFF; fix CiA 301 mapping tests (0x1A00 TPDO)
- Add test_pdo_iterate

Fixes flawed combined-PDO approach from PR canopen-python#613 (dummy zero offsets).

Author: surajSFDC

canopen/pdo/__init__.py

@@ -1,4 +1,7 @@
+import itertools
 import logging
+from collections.abc import Iterator, Mapping
+from typing import Union
 
 from canopen import node
 from canopen.pdo.base import PdoBase, PdoMap, PdoMaps, PdoVariable
@@ -17,6 +20,35 @@
 logger = logging.getLogger(__name__)
 
 
+class _CombinedPdoMaps(Mapping[int, PdoMap]):
+    """Combine RPDO and TPDO :class:`PdoMaps` without dummy zero offsets.
+
+    Avoids ``PdoMaps(0, 0, …)`` where ``__getitem__`` fallbacks would alias
+    ``key`` to ``key + 1`` (see discussion on PR #613).
+    """
+
+    def __init__(self, rx: PdoMaps, tx: PdoMaps):
+        self.rx = rx
+        self.tx = tx
+
+    def __getitem__(self, key: int) -> PdoMap:
+        for maps in (self.rx, self.tx):
+            try:
+                return maps[key]
+            except KeyError:
+                continue
+        raise KeyError(key)
+
+    def __iter__(self) -> Iterator[int]:
+        return itertools.chain(
+            (self.rx.map_offset + i - 1 for i in self.rx),
+            (self.tx.map_offset + i - 1 for i in self.tx),
+        )
+
+    def __len__(self) -> int:
+        return len(self.rx) + len(self.tx)
+
+
 class PDO(PdoBase):
     """PDO Class for backwards compatibility.
 
@@ -28,19 +60,30 @@ def __init__(self, node, rpdo, tpdo):
         super(PDO, self).__init__(node)
         self.rx = rpdo.map
         self.tx = tpdo.map
-
-        self.map = {}
-        # the object 0x1A00 equals to key '1' so we remove 1 from the key
-        for key, value in self.rx.items():
-            self.map[0x1A00 + (key - 1)] = value
-        for key, value in self.tx.items():
-            self.map[0x1600 + (key - 1)] = value
+        self.map = _CombinedPdoMaps(self.rx, self.tx)
+
+    def __getitem__(self, key: Union[int, str]):
+        if isinstance(key, int):
+            if key == 0:
+                raise KeyError("PDO index zero requested for 1-based sequence")
+            if 0 < key <= 512:
+                return self.map[key]
+            if 0x1400 <= key <= 0x17FF:
+                return self.rx[key]
+            if 0x1800 <= key <= 0x1BFF:
+                return self.tx[key]
+        for pdo_map in self.map.values():
+            try:
+                return pdo_map[key]
+            except KeyError:
+                continue
+        raise KeyError(f"PDO: {key} was not found in any map")
 
 
 class RPDO(PdoBase):
     """Receive PDO to transfer data from somewhere to the represented node.
 
-    Properties 0x1400 to 0x1403 | Mapping 0x1600 to 0x1603.
+    Properties 0x1400 to 0x15FF | Mapping 0x1600 to 0x17FF.
     :param object node: Parent node for this object.
     """
 
@@ -65,7 +108,7 @@ def stop(self):
 class TPDO(PdoBase):
     """Transmit PDO to broadcast data from the represented node to the network.
 
-    Properties 0x1800 to 0x1803 | Mapping 0x1A00 to 0x1A03.
+    Properties 0x1800 to 0x19FF | Mapping 0x1A00 to 0x1BFF.
     :param object node: Parent node for this object.
     """
 

canopen/pdo/base.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import binascii
+import contextlib
 import logging
 import math
 import threading
@@ -33,7 +34,7 @@ class PdoBase(Mapping):
 
     def __init__(self, node: Union[LocalNode, RemoteNode]):
         self.network: canopen.network.Network = canopen.network._UNINITIALIZED_NETWORK
-        self.map: Optional[PdoMaps] = None
+        self.map: Optional[Union[PdoMaps, Mapping[int, PdoMap]]] = None
         self.node: Union[LocalNode, RemoteNode] = node
 
     def __iter__(self):
@@ -45,8 +46,7 @@ def __getitem__(self, key: Union[int, str]):
                 raise KeyError("PDO index zero requested for 1-based sequence")
             if (
                 0 < key <= 512  # By PDO Index
-                or 0x1600 <= key <= 0x17FF  # By RPDO ID (512)
-                or 0x1A00 <= key <= 0x1BFF  # By TPDO ID (512)
+                or 0x1400 <= key <= 0x1BFF  # RPDO/TPDO communication or mapping record
             ):
                 return self.map[key]
         for pdo_map in self.map.values():
@@ -155,6 +155,8 @@ def __init__(self, com_offset, map_offset, pdo_node: PdoBase, cob_base=None):
         :param cob_base:
         """
         self.maps: dict[int, PdoMap] = {}
+        self.com_offset = com_offset
+        self.map_offset = map_offset
         for map_no in range(512):
             if com_offset + map_no in pdo_node.node.object_dictionary:
                 new_map = PdoMap(
@@ -167,7 +169,14 @@ def __init__(self, com_offset, map_offset, pdo_node: PdoBase, cob_base=None):
                 self.maps[map_no + 1] = new_map
 
     def __getitem__(self, key: int) -> PdoMap:
-        return self.maps[key]
+        try:
+            return self.maps[key]
+        except KeyError:
+            with contextlib.suppress(KeyError):
+                return self.maps[key + 1 - self.map_offset]
+            with contextlib.suppress(KeyError):
+                return self.maps[key + 1 - self.com_offset]
+            raise KeyError(key)
 
     def __iter__(self) -> Iterator[int]:
         return iter(self.maps)

test/test_pdo.py

@@ -49,10 +49,13 @@ def test_pdo_getitem(self):
         self.assertEqual(node.tpdo[1]['BOOLEAN value'].raw, False)
         self.assertEqual(node.tpdo[1]['BOOLEAN value 2'].raw, True)
 
-        # Test different types of access
-        by_mapping_record = node.pdo[0x1600]
+        # Test different types of access (0x1A00 = TPDO mapping per CiA 301)
+        by_mapping_record = node.pdo[0x1A00]
         self.assertIsInstance(by_mapping_record, canopen.pdo.PdoMap)
         self.assertEqual(by_mapping_record['INTEGER16 value'].raw, -3)
+        self.assertIs(node.tpdo[0x1A00], by_mapping_record)
+        self.assertIs(node.tpdo[0x1800], by_mapping_record)
+        self.assertIs(node.pdo[0x1800], by_mapping_record)
         by_object_name = node.pdo['INTEGER16 value']
         self.assertIsInstance(by_object_name, canopen.pdo.PdoVariable)
         self.assertIs(by_object_name.od, node.object_dictionary['INTEGER16 value'])
@@ -68,14 +71,27 @@ def test_pdo_getitem(self):
         self.assertEqual(by_object_index.raw, 0xf)
         self.assertIs(node.pdo['0x2002'], by_object_index)
         self.assertIs(node.tpdo[0x2002], by_object_index)
-        self.assertIs(node.pdo[0x1600][0x2002], by_object_index)
+        self.assertIs(node.pdo[0x1A00][0x2002], by_object_index)
 
         self.assertRaises(KeyError, lambda: node.pdo[0])
         self.assertRaises(KeyError, lambda: node.tpdo[0])
         self.assertRaises(KeyError, lambda: node.pdo['DOES NOT EXIST'])
         self.assertRaises(KeyError, lambda: node.pdo[0x1BFF])
         self.assertRaises(KeyError, lambda: node.tpdo[0x1BFF])
 
+    def test_pdo_iterate(self):
+        node = self.node
+        pdo_iter = iter(node.pdo.items())
+        prev = 0
+        for rpdo, (index, pdo) in zip(node.rpdo.values(), pdo_iter):
+            self.assertIs(rpdo, pdo)
+            self.assertGreater(index, prev)
+            prev = index
+        for tpdo, (index, pdo) in zip(node.tpdo.values(), pdo_iter):
+            self.assertIs(tpdo, pdo)
+            self.assertGreater(index, prev)
+            prev = index
+
     def test_pdo_maps_iterate(self):
         node = self.node
         self.assertEqual(len(node.pdo), sum(1 for _ in node.pdo))