possible fix and test for #381

src/canmatrix/canmatrix.py

@@ -47,7 +47,6 @@
 import canmatrix.copy
 import canmatrix.types
 import canmatrix.utils
-import copy
 
 if attr.__version__ < '17.4.0':  # type: ignore
     raise RuntimeError("need attrs >= 17.4.0")
@@ -69,8 +68,8 @@ class J1939needsExtendedIdetifier(ExceptionTemplate): pass
 
 def arbitration_id_converter(source):  # type: (typing.Union[int, ArbitrationId]) -> ArbitrationId
     """Converter for attrs which accepts ArbitrationId itself or int."""
-    temp_id = source if isinstance(source, ArbitrationId) else ArbitrationId.from_compound_integer(source)
-    return copy.deepcopy(temp_id)
+    return source if isinstance(source, ArbitrationId) else  ArbitrationId.from_compound_integer(source)
+
 
 @attr.s
 class Ecu(object):
@@ -721,7 +720,7 @@ class Frame(object):
 
     name = attr.ib(default="")  # type: str
     # mypy Unsupported converter:
-    arbitration_id = attr.ib(converter=arbitration_id_converter, default=arbitration_id_converter(0))  # type: ArbitrationId
+    arbitration_id = attr.ib(converter=arbitration_id_converter, default=0)  # type: ArbitrationId
     size = attr.ib(default=0)  # type: int
     transmitters = attr.ib(factory=list)  # type: typing.MutableSequence[str]
     # extended = attr.ib(default=False)  # type: bool

src/canmatrix/tests/test_canmatrix.py

@@ -805,6 +805,16 @@ def test_Arbitration_id():
     assert id_from_int_extended == id_extended
     assert id_from_int_extended != id_standard
 
+def test_arbitration_id_is_instance():
+    frame1 = canmatrix.Frame(name = "Frame1")
+    frame2 = canmatrix.Frame(name = "Frame1")
+
+    frame1.arbitration_id.id = 42
+
+    assert frame1.arbitration_id.id == 42
+    assert frame2.arbitration_id.id == 0
+
+
 
 @pytest.fixture
 def empty_matrix():