don't memoize objects that are their own copies (closes #12422)
Patch mostly by Alex Gaynor.
diff --git a/Lib/test/test_copy.py b/Lib/test/test_copy.py
index a84c109..e450f70 100644
--- a/Lib/test/test_copy.py
+++ b/Lib/test/test_copy.py
@@ -321,9 +321,24 @@
def test_deepcopy_keepalive(self):
memo = {}
- x = 42
+ x = []
y = copy.deepcopy(x, memo)
- self.assertTrue(memo[id(x)] is x)
+ self.assertIs(memo[id(memo)][0], x)
+
+ def test_deepcopy_dont_memo_immutable(self):
+ memo = {}
+ x = [1, 2, 3, 4]
+ y = copy.deepcopy(x, memo)
+ self.assertEqual(y, x)
+ # There's the entry for the new list, and the keep alive.
+ self.assertEqual(len(memo), 2)
+
+ memo = {}
+ x = [(1, 2)]
+ y = copy.deepcopy(x, memo)
+ self.assertEqual(y, x)
+ # Tuples with immutable contents are immutable for deepcopy.
+ self.assertEqual(len(memo), 2)
def test_deepcopy_inst_vanilla(self):
class C: