A temporary quick fix for dataclass serialization (#500)

dill/_dill.py

@@ -277,6 +277,10 @@ def get_file_type(*args, **kwargs):
 from collections import OrderedDict
 
 import inspect
+import dataclasses
+
+from pickle import GLOBAL
+
 
 ### Shims for different versions of Python and dill
 class Sentinel(object):
@@ -1826,30 +1830,13 @@ def save_dictproxy(pickler, obj):
         pickler.save_reduce(DictProxyType, (mapping,), obj=obj)
         log.info("# Mp")
         return
-elif not IS_PYPY:
-    if not OLD33:
-        @register(DictProxyType)
-        def save_dictproxy(pickler, obj):
-            log.info("Mp: %s" % obj)
-            pickler.save_reduce(DictProxyType, (obj.copy(),), obj=obj)
-            log.info("# Mp")
-            return
-    else:
-        # The following function is based on 'saveDictProxy' from spickle
-        # Copyright (c) 2011 by science+computing ag
-        # License: http://www.apache.org/licenses/LICENSE-2.0
-        @register(DictProxyType)
-        def save_dictproxy(pickler, obj):
-            log.info("Dp: %s" % obj)
-            attr = obj.get('__dict__')
-           #pickler.save_reduce(_create_dictproxy, (attr,'nested'), obj=obj)
-            if type(attr) == GetSetDescriptorType and attr.__name__ == "__dict__" \
-            and getattr(attr.__objclass__, "__dict__", None) == obj:
-                pickler.save_reduce(getattr, (attr.__objclass__,"__dict__"),obj=obj)
-                log.info("# Dp")
-                return
-            # all bad below... so throw ReferenceError or TypeError
-            raise ReferenceError("%s does not reference a class __dict__" % obj)
+else:
+    @register(DictProxyType)
+    def save_dictproxy(pickler, obj):
+        log.info("Mp: %s" % obj)
+        pickler.save_reduce(DictProxyType, (obj.copy(),), obj=obj)
+        log.info("# Mp")
+        return
 
 @register(SliceType)
 def save_slice(pickler, obj):
@@ -2258,6 +2245,33 @@ def save_capsule(pickler, obj):
 else:
     _testcapsule = None
 
+
+#############################
+# A quick fix for issue #500
+# This should be removed when a better solution is found.
+
+if hasattr(dataclasses, "_HAS_DEFAULT_FACTORY_CLASS"):
+    @register(dataclasses._HAS_DEFAULT_FACTORY_CLASS)
+    def save_dataclasses_HAS_DEFAULT_FACTORY_CLASS(pickler, obj):
+        pickler.write(GLOBAL + b"dataclasses\n_HAS_DEFAULT_FACTORY\n")
+
+if hasattr(dataclasses, "MISSING"):
+    @register(type(dataclasses.MISSING))
+    def save_dataclasses_MISSING_TYPE(pickler, obj):
+        pickler.write(GLOBAL + b"dataclasses\nMISSING\n")
+
+if hasattr(dataclasses, "KW_ONLY"):
+    @register(type(dataclasses.KW_ONLY))
+    def save_dataclasses_KW_ONLY_TYPE(pickler, obj):
+        pickler.write(GLOBAL + b"dataclasses\nKW_ONLY\n")
+
+if hasattr(dataclasses, "_FIELD_BASE"):
+    @register(dataclasses._FIELD_BASE)
+    def save_dataclasses_FIELD_BASE(pickler, obj):
+        pickler.write(GLOBAL + b"dataclasses\n" + obj.name.encode() + b"\n")
+
+#############################
+
 # quick sanity checking
 def pickles(obj,exact=False,safe=False,**kwds):
     """

tests/test_dataclasses.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+#
+# Author: Mike McKerns (mmckerns @caltech and @uqfoundation)
+# Author: Anirudh Vegesana (avegesan@cs.stanford.edu)
+# Copyright (c) 2022 The Uncertainty Quantification Foundation.
+# License: 3-clause BSD.  The full license text is available at:
+#  - https://github.com/uqfoundation/dill/blob/master/LICENSE
+"""
+test pickling a dataclass
+"""
+
+import dill
+import dataclasses
+
+def test_dataclasses():
+    # Issue #500
+    @dataclasses.dataclass
+    class A:
+        x: int
+        y: str
+
+    @dataclasses.dataclass
+    class B:
+        a: A
+
+    a = A(1, "test")
+    before = B(a)
+    save = dill.dumps(before)
+    after = dill.loads(save)
+    assert before != after # classes don't match
+    assert before == B(A(**dataclasses.asdict(after.a)))
+    assert dataclasses.asdict(before) == dataclasses.asdict(after)
+
+if __name__ == '__main__':
+    test_dataclasses()

tests/test_dictviews.py

@@ -7,7 +7,10 @@
 #  - https://github.com/uqfoundation/dill/blob/master/LICENSE
 
 import dill
-from dill._dill import OLD310, MAPPING_PROXY_TRICK
+from dill._dill import OLD310, MAPPING_PROXY_TRICK, DictProxyType
+
+def test_dictproxy():
+    assert dill.copy(DictProxyType({'a': 2}))
 
 def test_dictviews():
     x = {'a': 1}
@@ -31,5 +34,6 @@ def test_dictproxy_trick():
         assert dict(seperate_views[1]) == new_x
 
 if __name__ == '__main__':
+    test_dictproxy()
     test_dictviews()
     test_dictproxy_trick()