Attempt to fix loading of simple OmegaConf pickled configs stored in 2.0

MANIFEST.in

@@ -1,3 +1,3 @@
 include LICENSE
 include requirements/base.txt
-recursive-include tests *.py
+recursive-include tests *.py *.pickle

omegaconf/basecontainer.py

@@ -103,7 +103,19 @@ def __setstate__(self, d: Dict[str, Any]) -> None:
 
         if isinstance(self, DictConfig):
             key_type = d["_metadata"].key_type
+
+            # backward compatibility to load OmegaConf 2.0 configs
+            if key_type is None:
+                key_type = Any
+                d["_metadata"].key_type = key_type
+
         element_type = d["_metadata"].element_type
+
+        # backward compatibility to load OmegaConf 2.0 configs
+        if element_type is None:
+            element_type = Any
+            d["_metadata"].element_type = element_type
+
         ref_type = d["_metadata"].ref_type
         if is_container_annotation(ref_type):
             if is_generic_dict(ref_type):

tests/data/load.py

@@ -0,0 +1,8 @@
+import pickle
+import sys
+
+from omegaconf import OmegaConf
+
+with open(f"{sys.argv[1]}.pickle", mode="rb") as fp:
+    cfg = pickle.load(fp)
+    assert cfg == OmegaConf.create({"a": [{"b": 10}]})

tests/data/save.py

@@ -0,0 +1,8 @@
+import pickle
+
+from omegaconf import OmegaConf, __version__
+
+cfg = OmegaConf.create({"a": [{"b": 10}]})
+
+with open(f"{__version__}.pickle", mode="wb") as fp:
+    pickle.dump(cfg, fp)

tests/test_serialization.py

@@ -65,7 +65,7 @@ def test_load_from_invalid() -> None:
         ({"foo": 10, "bar": "${foo}"}, False, None, str),
         ({"foo": 10, "bar": "${foo}"}, False, None, pathlib.Path),
         ({"foo": 10, "bar": "${foo}"}, False, {"foo": 10, "bar": 10}, str),
-        ([u"שלום"], False, None, str),
+        (["שלום"], False, None, str),
     ],
 )
 class TestSaveLoad:
@@ -257,3 +257,17 @@ def test_pickle_flags_consistency() -> None:
     cfg2._set_flag("test", None)
     assert cfg2._get_flag("test") is None
     assert cfg2._get_node("a")._get_flag("test") is None
+
+
+@mark.parametrize(
+    "version",
+    [
+        "2.0.6",
+        "2.1.0.rc1",
+    ],
+)
+def test_pickle_backward_compatibility(version: str) -> None:
+    path = Path(__file__).parent / "data" / f"{version}.pickle"
+    with open(path, mode="rb") as fp:
+        cfg = pickle.load(fp)
+        assert cfg == OmegaConf.create({"a": [{"b": 10}]})