__getstate__: preempt python3.6 Optional pickle err

Author: Jasha10

omegaconf/basecontainer.py

@@ -14,6 +14,7 @@
     _is_missing_literal,
     _is_missing_value,
     _is_none,
+    _is_union,
     _resolve_optional,
     get_ref_type,
     get_structured_config_data,
@@ -29,6 +30,7 @@
 from .base import Container, ContainerMetadata, DictKeyType, Node, SCMode
 from .errors import (
     ConfigCycleDetectedException,
+    ConfigSerializationError,
     ConfigTypeError,
     InterpolationResolutionError,
     MissingMandatoryValue,
@@ -99,6 +101,12 @@ def __getstate__(self) -> Dict[str, Any]:
                 dict_copy["_metadata"].ref_type = List
             else:
                 assert False
+        if sys.version_info < (3, 7):
+            element_type = self._metadata.element_type
+            if _is_union(element_type):
+                raise ConfigSerializationError(
+                    "Serializing structured configs with `Union` element type requires python >= 3.7"
+                )
         return dict_copy
 
     # Support pickle

omegaconf/errors.py

@@ -139,3 +139,9 @@ class GrammarParseError(OmegaConfBaseException):
     """
     Thrown when failing to parse an expression according to the ANTLR grammar.
     """
+
+
+class ConfigSerializationError(OmegaConfBaseException):
+    """
+    Thrown when an error occurs during serialization of an OmegaConf object.
+    """

tests/test_serialization.py

@@ -13,7 +13,7 @@
 
 from omegaconf import MISSING, DictConfig, ListConfig, OmegaConf
 from omegaconf._utils import get_ref_type
-from omegaconf.errors import OmegaConfBaseException
+from omegaconf.errors import ConfigSerializationError
 from tests import (
     Color,
     PersonA,
@@ -356,15 +356,12 @@ def test_pickle_backward_compatibility(version: str) -> None:
 
 
 @mark.skipif(sys.version_info >= (3, 7), reason="requires python3.6")
-@mark.xfail(reason="python3.6 pickling error is not handled")
 def test_python36_pickle_optional() -> None:
     cfg = OmegaConf.structured(SubscriptedDictOpt)
     with raises(
-        OmegaConfBaseException,
+        ConfigSerializationError,
         match=re.escape(
-            "Serializing structured configs with `Union` type annotations requires python >= 3.7"
+            "Serializing structured configs with `Union` element type requires python >= 3.7"
         ),
     ):
-        # currently this raises the following:
-        # _pickle.PicklingError: Can't pickle typing.Union[int, NoneType]: it's not the same object as typing.Union
         pickle.dumps(cfg)