bpo-37972: unittest.mock._Call now passes on __getitem__ to the __getattr__ chaining so that call() can be subscriptable

Lib/unittest/mock.py

@@ -2428,6 +2428,12 @@ def __getattr__(self, attr):
         return _Call(name=name, parent=self, from_kall=False)
 
 
+    def __getattribute__(self, attr):
+        if attr in tuple.__dict__:
+            raise AttributeError
+        return tuple.__getattribute__(self, attr)
+
+
     def count(self, /, *args, **kwargs):
         return self.__getattr__('count')(*args, **kwargs)
 

Lib/unittest/test/testmock/testhelpers.py

@@ -334,6 +334,26 @@ def test_call_with_name(self):
         self.assertEqual(_Call((('bar', 'barz'),),)[0], '')
         self.assertEqual(_Call((('bar', 'barz'), {'hello': 'world'}),)[0], '')
 
+    def test_dunder_call(self):
+        m = MagicMock()
+        m().foo()['bar']()
+        self.assertEqual(
+            m.mock_calls,
+            [call(), call().foo(), call().foo().__getitem__('bar'), call().foo().__getitem__()()]
+        )
+        m = MagicMock()
+        m().foo()['bar'] = 1
+        self.assertEqual(
+            m.mock_calls,
+            [call(), call().foo(), call().foo().__setitem__('bar', 1)]
+        )
+        m = MagicMock()
+        iter(m().foo())
+        self.assertEqual(
+            m.mock_calls,
+            [call(), call().foo(), call().foo().__iter__()]
+        )
+
 
 class SpecSignatureTest(unittest.TestCase):
 

Misc/NEWS.d/next/Library/2019-08-28-21-40-12.bpo-37972.kP-n4L.rst

@@ -0,0 +1,5 @@
+Subscripts to the `unittest.mock.call` objects now receive the same chaining mechanism as any other custom attributes, so that the following usage no longer raises a `TypeError`:
+
+    call().foo().__getitem__('bar')
+
+Patch by blhsing