[3.12] gh-119600: mock: do not access attributes of original when new_callable is set (GH-119601)

Lib/test/test_unittest/testmock/support.py

@@ -14,3 +14,14 @@ def wibble(self): pass
 
 class X(object):
     pass
+
+# A standin for weurkzeug.local.LocalProxy - issue 119600
+def _inaccessible(*args, **kwargs):
+    raise AttributeError
+
+
+class OpaqueProxy:
+    __getattribute__ = _inaccessible
+
+
+g = OpaqueProxy()

Lib/test/test_unittest/testmock/testpatch.py

@@ -2045,6 +2045,13 @@ def test(): pass
         with self.assertRaises(TypeError):
             test()
 
+    def test_patch_proxy_object(self):
+        @patch("test.test_unittest.testmock.support.g", new_callable=MagicMock())
+        def test(_):
+            pass
+
+        test()
+
 
 if __name__ == '__main__':
     unittest.main()

Lib/unittest/mock.py

@@ -1478,13 +1478,12 @@ def __enter__(self):
                 if isinstance(original, type):
                     # If we're patching out a class and there is a spec
                     inherit = True
-            if spec is None and _is_async_obj(original):
-                Klass = AsyncMock
-            else:
-                Klass = MagicMock
-            _kwargs = {}
+
+            # Determine the Klass to use
             if new_callable is not None:
                 Klass = new_callable
+            elif spec is None and _is_async_obj(original):
+                Klass = AsyncMock
             elif spec is not None or spec_set is not None:
                 this_spec = spec
                 if spec_set is not None:
@@ -1497,7 +1496,12 @@ def __enter__(self):
                     Klass = AsyncMock
                 elif not_callable:
                     Klass = NonCallableMagicMock
+                else:
+                    Klass = MagicMock
+            else:
+                Klass = MagicMock
 
+            _kwargs = {}
             if spec is not None:
                 _kwargs['spec'] = spec
             if spec_set is not None:

Misc/NEWS.d/next/Library/2024-06-10-14-00-40.gh-issue-119600.jJMf4C.rst

@@ -0,0 +1,2 @@
+Fix :func:`unittest.mock.patch` to not read attributes of the target when
+``new_callable`` is set. Patch by Robert Collins.