Issue #7689: Allow pickling of dynamically created classes when their

metaclass is registered with copyreg.  Patch by Nicolas M. Thiéry and
Craig Citro.

Lib/pickle.py

@@ -297,20 +297,20 @@ class _Pickler:
             f(self, obj) # Call unbound method with explicit self
             return
 
-        # Check for a class with a custom metaclass; treat as regular class
-        try:
-            issc = issubclass(t, type)
-        except TypeError: # t is not a class (old Boost; see SF #502085)
-            issc = 0
-        if issc:
-            self.save_global(obj)
-            return
-
         # Check copyreg.dispatch_table
         reduce = dispatch_table.get(t)
         if reduce:
             rv = reduce(obj)
         else:
+            # Check for a class with a custom metaclass; treat as regular class
+            try:
+                issc = issubclass(t, type)
+            except TypeError: # t is not a class (old Boost; see SF #502085)
+                issc = False
+            if issc:
+                self.save_global(obj)
+                return
+
             # Check for a __reduce_ex__ method, fall back to __reduce__
             reduce = getattr(obj, "__reduce_ex__", None)
             if reduce:

Lib/test/pickletester.py

@@ -122,6 +122,19 @@ class metaclass(type):
 class use_metaclass(object, metaclass=metaclass):
     pass
 
+class pickling_metaclass(type):
+    def __eq__(self, other):
+        return (type(self) == type(other) and
+                self.reduce_args == other.reduce_args)
+
+    def __reduce__(self):
+        return (create_dynamic_class, self.reduce_args)
+
+def create_dynamic_class(name, bases):
+    result = pickling_metaclass(name, bases, dict())
+    result.reduce_args = (name, bases)
+    return result
+
 # DATA0 .. DATA2 are the pickles we expect under the various protocols, for
 # the object returned by create_data().
 
@@ -696,6 +709,14 @@ class AbstractPickleTests(unittest.TestCase):
             b = self.loads(s)
             self.assertEqual(a.__class__, b.__class__)
 
+    def test_dynamic_class(self):
+        a = create_dynamic_class("my_dynamic_class", (object,))
+        copyreg.pickle(pickling_metaclass, pickling_metaclass.__reduce__)
+        for proto in protocols:
+            s = self.dumps(a, proto)
+            b = self.loads(s)
+            self.assertEqual(a, b)
+
     def test_structseq(self):
         import time
         import os