gh-100287: Fix unittest.mock.seal with AsyncMock (#100496)

Backports: e4b43ebb3afbd231a4e5630e7e358aa3093f8677
Signed-off-by: Chris Withers <chris@simplistix.co.uk>

Author: hauntsaninja

NEWS.d/2022-12-24-08-42-05.gh-issue-100287.n0oEuG.rst

@@ -0,0 +1 @@
+Fix the interaction of :func:`unittest.mock.seal` with :class:`unittest.mock.AsyncMock`.

mock/mock.py

@@ -1027,15 +1027,15 @@ def _get_child_mock(self, **kw):
 
         For non-callable mocks the callable variant will be used (rather than
         any custom subclass)."""
-        _new_name = kw.get("_new_name")
-        if _new_name in self.__dict__['_spec_asyncs']:
-            return AsyncMock(**kw)
-
         if self._mock_sealed:
             attribute = f".{kw['name']}" if "name" in kw else "()"
             mock_name = self._extract_mock_name() + attribute
             raise AttributeError(mock_name)
 
+        _new_name = kw.get("_new_name")
+        if _new_name in self.__dict__['_spec_asyncs']:
+            return AsyncMock(**kw)
+
         _type = type(self)
         if issubclass(_type, MagicMock) and _new_name in _async_method_magics:
             # Any asynchronous magic becomes an AsyncMock

mock/tests/testasync.py

@@ -7,7 +7,7 @@
 from contextlib import contextmanager
 
 from mock import (ANY, call, AsyncMock, patch, MagicMock, Mock,
-                  create_autospec, sentinel)
+                  create_autospec, sentinel, seal)
 from mock.backports import IsolatedAsyncioTestCase, iscoroutinefunction
 from mock.mock import _CallList
 
@@ -306,6 +306,14 @@ def test_spec_normal_methods_on_class_with_mock(self):
         self.assertIsInstance(mock.async_method, AsyncMock)
         self.assertIsInstance(mock.normal_method, Mock)
 
+    def test_spec_normal_methods_on_class_with_mock_seal(self):
+        mock = Mock(AsyncClass)
+        seal(mock)
+        with self.assertRaises(AttributeError):
+            mock.normal_method
+        with self.assertRaises(AttributeError):
+            mock.async_method
+
     def test_spec_async_attributes_instance(self):
         async_instance = AsyncClass()
         async_instance.async_func_attr = async_func
@@ -1097,3 +1105,7 @@ async def f(x=None): pass
                 )) as cm:
             self.mock.assert_has_awaits([call(), call(1, 2)])
         self.assertIsInstance(cm.exception.__cause__, TypeError)
+
+
+if __name__ == '__main__':
+    unittest.main()