copy values in Config.merge

IPython/config/loader.py

@@ -200,14 +200,14 class Config(dict):
         to_update = {}
         for k, v in iteritems(other):
             if k not in self:
-                to_update[k] = v
+                to_update[k] = copy.deepcopy(v)
             else: # I have this key
                 if isinstance(v, Config) and isinstance(self[k], Config):
                     # Recursively merge common sub Configs
                     self[k].merge(v)
                 else:
                     # Plain updates for non-Configs
-                    to_update[k] = v
+                    to_update[k] = copy.deepcopy(v)
 
         self.update(to_update)
 

IPython/config/tests/test_configurable.py

@@ -357,4 +357,19 class TestConfigContainers(TestCase):
         obj = Containers(config=c)
         self.assertEqual(obj.d, {'a':'b', 'c':'d', 'e':'f'})
     
+    def test_update_twice(self):
+        c = Config()
+        c.MyConfigurable.a = 5
+        m = MyConfigurable(config=c)
+        self.assertEqual(m.a, 5)
+        
+        c2 = Config()
+        c2.MyConfigurable.a = 10
+        m.update_config(c2)
+        self.assertEqual(m.a, 10)
+        
+        c2.MyConfigurable.a = 15
+        m.update_config(c2)
+        self.assertEqual(m.a, 15)
+    
 

IPython/config/tests/test_loader.py

@@ -324,4 +324,14 class TestConfig(TestCase):
         foo = cfg['foo']
         assert isinstance(foo, LazyConfigValue)
         self.assertIn('foo', cfg)
+    
+    def test_merge_copies(self):
+        c = Config()
+        c2 = Config()
+        c2.Foo.trait = []
+        c.merge(c2)
+        c2.Foo.trait.append(1)
+        self.assertIsNot(c.Foo, c2.Foo)
+        self.assertEqual(c.Foo.trait, [])
+        self.assertEqual(c2.Foo.trait, [1])