1. The __copy__ method should also copy attribute. 2. Update test code to cover this.

Author: WindSoilder

exceptiongroup/__init__.py

@@ -43,12 +43,13 @@ def __init__(self, message, exceptions, sources):
             )
 
     # copy.copy doesn't work for ExceptionGroup, because BaseException have
-    # rewrite __reduce_ex__ method.  So we need to add __copy__ method to
+    # rewrite __reduce_ex__ method.  We need to add __copy__ method to
     # make it can be copied.
     def __copy__(self):
         new_group = self.__class__(self.message, self.exceptions, self.sources)
         new_group.__traceback__ = self.__traceback__
         new_group.__context__ = self.__context__
+        new_group.__cause__ = self.__cause__
         return new_group
 
 

exceptiongroup/_tests/test_tools.py

@@ -5,6 +5,15 @@ def raise_error(err):
     raise err
 
 
+def raise_error_from_another(out_err, another_err):
+    # use try..except approache so out_error have meaningful
+    # __context__, __cause__ attribute.
+    try:
+        raise another_err
+    except Exception as e:
+        raise out_err from e
+
+
 def test_split_for_none_exception():
     matched, unmatched = split(RuntimeError, None)
     assert matched is None
@@ -79,7 +88,7 @@ def test_split_with_single_exception():
     assert unmatched is err
 
 
-def test_split_with_same_traceback():
+def test_split_and_check_attributes_same():
     try:
         raise_error(RuntimeError("RuntimeError"))
     except Exception as e:
@@ -93,11 +102,16 @@ def test_split_with_same_traceback():
     group = ExceptionGroup(
         "ErrorGroup", [run_error, val_error], ["RuntimeError", "ValueError"]
     )
+    # go and check __traceback__, __cause__ attributes
     try:
-        raise_error(group)
+        raise_error_from_another(group, RuntimeError("Cause"))
     except BaseException as e:
         new_group = e
 
     matched, unmatched = split(RuntimeError, group)
     assert matched.__traceback__ is new_group.__traceback__
+    assert matched.__cause__ is new_group.__cause__
+    assert matched.__context__ is new_group.__context__
     assert unmatched.__traceback__ is new_group.__traceback__
+    assert unmatched.__cause__ is new_group.__cause__
+    assert unmatched.__context__ is new_group.__context__