fix: SourceOperator is_source default broken by name mangling

amber/src/main/python/core/models/operator.py

@@ -164,7 +164,7 @@ def on_finish(self, port: int) -> Iterator[Optional[TupleLike]]:
 
 
 class SourceOperator(TupleOperatorV2):
-    __internal_is_source = True
+    _Operator__internal_is_source = True
 
     @abstractmethod
     def produce(self) -> Iterator[Union[TupleLike, TableLike, None]]:
@@ -267,7 +267,7 @@ class TableOperator(TupleOperatorV2):
 
     def __init__(self):
         super().__init__()
-        self.__internal_is_source: bool = False
+        self._Operator__internal_is_source: bool = False
         self.__table_data: Mapping[int, List[Tuple]] = defaultdict(list)
 
     @overrides.final

amber/src/test/python/core/models/test_operator.py

@@ -154,30 +154,7 @@ def test_setter_can_flip_back_to_false(self):
         op.is_source = False
         assert op.is_source is False
 
-    def test_source_operator_class_attr_storage_diverges_from_property_read(
-        self,
-    ):
-        # Documents the underlying defect without claiming a contract: the class
-        # attribute is stored under one mangled name, the property reads from
-        # another, so they cannot agree. Asserting the two attributes directly
-        # decouples this from the eventual is_source-on-SourceOperator fix.
-        src = _ConcreteSource()
-        # The mangled attribute SourceOperator set — present but unused:
-        assert getattr(src, "_SourceOperator__internal_is_source") is True
-        # The attribute Operator.is_source actually reads — still the default:
-        assert getattr(src, "_Operator__internal_is_source") is False
-
-    @pytest.mark.xfail(
-        strict=True,
-        reason=(
-            "Known bug: SourceOperator's __internal_is_source class attribute "
-            "is name-mangled to _SourceOperator__internal_is_source, while "
-            "Operator.is_source reads _Operator__internal_is_source. The "
-            "intended contract is is_source=True on SourceOperator instances; "
-            "this xfail flips to XPASS when the bug is fixed."
-        ),
-    )
-    def test_source_operator_subclass_should_report_is_source_true(self):
+    def test_source_operator_subclass_reports_is_source_true(self):
         src = _ConcreteSource()
         assert src.is_source is True