Issue #11480: Fixed copy.copy to work with classes with custom metaclasses.

Patch by Daniel Urban.

Lib/copy.py

@@ -76,6 +76,14 @@ def copy(x):
     if copier:
         return copier(x)
 
+    try:
+        issc = issubclass(cls, type)
+    except TypeError: # cls is not a class
+        issc = False
+    if issc:
+        # treat it as a regular class:
+        return _copy_immutable(x)
+
     copier = getattr(cls, "__copy__", None)
     if copier:
         return copier(x)

Lib/test/test_copy.py

@@ -3,6 +3,7 @@
 import copy
 import copyreg
 import weakref
+import abc
 from operator import le, lt, ge, gt, eq, ne
 
 import unittest
@@ -93,9 +94,11 @@ class TestCopy(unittest.TestCase):
             pass
         def f():
             pass
+        class WithMetaclass(metaclass=abc.ABCMeta):
+            pass
         tests = [None, 42, 2**100, 3.14, True, False, 1j,
                  "hello", "hello\u1234", f.__code__,
-                 NewStyle, range(10), Classic, max]
+                 NewStyle, range(10), Classic, max, WithMetaclass]
         for x in tests:
             self.assertIs(copy.copy(x), x)
 

Misc/NEWS

@@ -24,6 +24,9 @@ Library
 - Fixed _pickle.Unpickler to not fail when loading empty strings as
   persistent IDs.
 
+- Issue #11480: Fixed copy.copy to work with classes with custom metaclasses.
+  Patch by Daniel Urban.
+
 - Issue #6477: Added support for pickling the types of built-in singletons
   (i.e., Ellipsis, NotImplemented, None).