fix pickling of bytes subclasses

Author: cosminbasca

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/bytes/BytesBuiltins.java

@@ -34,6 +34,7 @@
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__CONTAINS__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__EQ__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__GETITEM__;
+import static com.oracle.graal.python.nodes.SpecialMethodNames.__GETNEWARGS__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__GE__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__GT__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__IMOD__;
@@ -2788,4 +2789,13 @@ protected static byte[] getBytes(PythonObjectLibrary lib, Object object) {
             throw new IllegalStateException(e);
         }
     }
+
+    @Builtin(name = __GETNEWARGS__, minNumOfPositionalArgs = 1)
+    @GenerateNodeFactory
+    public abstract static class GetNewargsNode extends PythonUnaryBuiltinNode {
+        @Specialization
+        PTuple doBytes(PBytes self) {
+            return factory().createTuple(new Object[]{factory().createBytes(self.getSequenceStorage())});
+        }
+    }
 }

graalpython/lib-graalpython/object.py

@@ -71,12 +71,14 @@ def _get_new_arguments(obj):
 
 def reduce_newobj(obj):
     cls = obj.__class__
-    if not cls.__dict__.get('__new__', None):
+    if not hasattr(cls, '__new__'):
         raise TypeError("cannot pickle '{}' object".format(cls.__name__))
 
     args, kwargs = _get_new_arguments(obj)
     import_copyreg()
 
+    hasargs = args is not None
+
     if kwargs is None or len(kwargs) == 0:
         newobj = copyreg.__newobj__
         newargs = (cls, ) + (args if args else tuple())
@@ -93,8 +95,9 @@ def reduce_newobj(obj):
     try:
         getstate = obj.__getstate__
     except AttributeError:
+        required = not hasargs and not isinstance(obj, (list, dict))
         itemsize = getattr(type(obj), '__itemsize__', 0)
-        if itemsize != 0:
+        if required and itemsize != 0:
             raise TypeError("cannot pickle '{}' object".format(cls.__name__))
 
         state = getattr(obj, "__dict__", None)