Adding test for default value immutability

swansonk14 · Jun 28, 2023 · 7f12646 · 7f12646
1 parent c48ef74
commit 7f12646
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Showing 2 changed files with 17 additions and 1 deletion.
diff --git a/tap/tap.py b/tap/tap.py
@@ -456,7 +456,7 @@ def parse_args(self: TapType,
                     elif var_type in (Tuple, tuple):
                         value = tuple(value)
 
-            # Set variable in self (and deepcopy)
+            # Set variable in self (and deepcopy to prevent mutation of default values)
             setattr(self, variable, deepcopy(value))
 
         # Process args

diff --git a/tests/test_integration.py b/tests/test_integration.py
@@ -1601,5 +1601,21 @@ class Desc(Tap):
         self.assertNotIn("I do not exist", help_desc)
 
 
+class TestDefaultImmutability(TestCase):
+    def test_default_immutability(self):
+        holy_hand_grenada = [1, 2, 5]  # no, 3 sir!
+
+        class DefaultImmutabilityTap(Tap):
+            array: list[int] = holy_hand_grenada
+
+        args = DefaultImmutabilityTap().parse_args([])
+
+        self.assertEqual(args.array, holy_hand_grenada)
+
+        holy_hand_grenada[2] = 3
+
+        self.assertEqual(args.array, [1, 2, 5])
+
+
 if __name__ == '__main__':
     unittest.main()