Issue #1100562: Fix deep-copying of objects derived from the list and dict types.

Patch by Michele Orrù and Björn Lindqvist.

Lib/copy.py

@@ -283,17 +283,7 @@ def _reconstruct(x, info, deep, memo=None):
         args = deepcopy(args, memo)
     y = callable(*args)
     memo[id(x)] = y
-    if listiter is not None:
-        for item in listiter:
-            if deep:
-                item = deepcopy(item, memo)
-            y.append(item)
-    if dictiter is not None:
-        for key, value in dictiter:
-            if deep:
-                key = deepcopy(key, memo)
-                value = deepcopy(value, memo)
-            y[key] = value
+
     if state:
         if deep:
             state = deepcopy(state, memo)
@@ -309,6 +299,18 @@ def _reconstruct(x, info, deep, memo=None):
             if slotstate is not None:
                 for key, value in slotstate.items():
                     setattr(y, key, value)
+
+    if listiter is not None:
+        for item in listiter:
+            if deep:
+                item = deepcopy(item, memo)
+            y.append(item)
+    if dictiter is not None:
+        for key, value in dictiter:
+            if deep:
+                key = deepcopy(key, memo)
+                value = deepcopy(value, memo)
+            y[key] = value
     return y
 
 del d
@@ -370,6 +372,16 @@ def _test():
     print(map(reprlib.repr, l1))
     print(map(reprlib.repr, l2))
     print(map(reprlib.repr, l3))
+    class odict(dict):
+        def __init__(self, d = {}):
+            self.a = 99
+            dict.__init__(self, d)
+        def __setitem__(self, k, i):
+            dict.__setitem__(self, k, i)
+            self.a
+    o = odict({"A" : "B"})
+    x = deepcopy(o)
+    print(o, x)
 
 if __name__ == '__main__':
     _test()

Lib/test/test_copy.py

@@ -532,6 +532,26 @@ class TestCopy(unittest.TestCase):
         self.assertEqual(x.foo, y.foo)
         self.assertTrue(x.foo is not y.foo)
 
+    def test_deepcopy_dict_subclass(self):
+        class C(dict):
+            def __init__(self, d=None):
+                if not d:
+                    d = {}
+                self._keys = list(d.keys())
+                super().__init__(d)
+            def __setitem__(self, key, item):
+                super().__setitem__(key, item)
+                if key not in self._keys:
+                    self._keys.append(key)
+        x = C(d={'foo':0})
+        y = copy.deepcopy(x)
+        self.assertEqual(x, y)
+        self.assertEqual(x._keys, y._keys)
+        self.assertTrue(x is not y)
+        x['bar'] = 1
+        self.assertNotEqual(x, y)
+        self.assertNotEqual(x._keys, y._keys)
+
     def test_copy_list_subclass(self):
         class C(list):
             pass

Misc/NEWS

@@ -158,6 +158,9 @@ Extensions
 Library
 -------
 
+- Issue #1100562: Fix deep-copying of objects derived from the list and
+  dict types.  Patch by Michele Orrù and Björn Lindqvist.
+
 - Issue #9753: Fixed socket.dup, which did not always work correctly
   on Windows.