bpo-35226: Fix equality for nested unittest.mock.call objects. (#10555)

Also refactor the call recording imolementation and add some notes
about its limitations.

Lib/unittest/test/testmock/testmock.py

@@ -925,6 +925,57 @@ class MockTest(unittest.TestCase):
                              call().__int__().call_list())
 
 
+    def test_child_mock_call_equal(self):
+        m = Mock()
+        result = m()
+        result.wibble()
+        # parent looks like this:
+        self.assertEqual(m.mock_calls, [call(), call().wibble()])
+        # but child should look like this:
+        self.assertEqual(result.mock_calls, [call.wibble()])
+
+
+    def test_mock_call_not_equal_leaf(self):
+        m = Mock()
+        m.foo().something()
+        self.assertNotEqual(m.mock_calls[1], call.foo().different())
+        self.assertEqual(m.mock_calls[0], call.foo())
+
+
+    def test_mock_call_not_equal_non_leaf(self):
+        m = Mock()
+        m.foo().bar()
+        self.assertNotEqual(m.mock_calls[1], call.baz().bar())
+        self.assertNotEqual(m.mock_calls[0], call.baz())
+
+
+    def test_mock_call_not_equal_non_leaf_params_different(self):
+        m = Mock()
+        m.foo(x=1).bar()
+        # This isn't ideal, but there's no way to fix it without breaking backwards compatibility:
+        self.assertEqual(m.mock_calls[1], call.foo(x=2).bar())
+
+
+    def test_mock_call_not_equal_non_leaf_attr(self):
+        m = Mock()
+        m.foo.bar()
+        self.assertNotEqual(m.mock_calls[0], call.baz.bar())
+
+
+    def test_mock_call_not_equal_non_leaf_call_versus_attr(self):
+        m = Mock()
+        m.foo.bar()
+        self.assertNotEqual(m.mock_calls[0], call.foo().bar())
+
+
+    def test_mock_call_repr(self):
+        m = Mock()
+        m.foo().bar().baz.bob()
+        self.assertEqual(repr(m.mock_calls[0]), 'call.foo()')
+        self.assertEqual(repr(m.mock_calls[1]), 'call.foo().bar()')
+        self.assertEqual(repr(m.mock_calls[2]), 'call.foo().bar().baz.bob()')
+
+
     def test_subclassing(self):
         class Subclass(Mock):
             pass