[Python-checkins] bpo-36593: Fix isinstance check for Mock objects with spec executed under tracing (GH-12790)

[Pablo Galindo]

https://github.com/python/cpython/commit/830b43d03cc47a27a22a50d777f23c8e60820867
commit: 830b43d03cc47a27a22a50d777f23c8e60820867
branch: master
author: Xtreak <tir.karthi at gmail.com>
committer: Pablo Galindo <Pablogsal at gmail.com>
date: 2019-04-13T20:12:33+01:00
summary:

bpo-36593: Fix isinstance check for Mock objects with spec executed under tracing (GH-12790)

In Python having a trace function in effect while mock is imported causes isinstance to be wrong for MagicMocks. This is due to the usage of super() in some class methods, as this sets the __class__ attribute. To avoid this, as a workaround, alias the usage of super .

files:
A Misc/NEWS.d/next/Library/2019-04-11-22-11-24.bpo-36598.hfzDUl.rst
M Lib/unittest/mock.py
M Lib/unittest/test/testmock/testmock.py

diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 8684f1dfa572..0e77f0e48943 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -739,7 +739,7 @@ def __delattr__(self, name):
 
         obj = self._mock_children.get(name, _missing)
         if name in self.__dict__:
-            super().__delattr__(name)
+            _safe_super(NonCallableMock, self).__delattr__(name)
         elif obj is _deleted:
             raise AttributeError(name)
         if obj is not _missing:
diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 66a5720d1432..37f14c37f47d 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1847,6 +1847,44 @@ def foo(a, b):
         self.assertRaises(TypeError, mock.child, 1)
         self.assertEqual(mock.mock_calls, [call.child(1, 2)])
 
+    def test_isinstance_under_settrace(self):
+        # bpo-36593 : __class__ is not set for a class that has __class__
+        # property defined when it's used with sys.settrace(trace) set.
+        # Delete the module to force reimport with tracing function set
+        # restore the old reference later since there are other tests that are
+        # dependent on unittest.mock.patch. In testpatch.PatchTest
+        # test_patch_dict_test_prefix and test_patch_test_prefix not restoring
+        # causes the objects patched to go out of sync
+
+        old_patch = unittest.mock.patch
+
+        # Directly using __setattr__ on unittest.mock causes current imported
+        # reference to be updated. Use a lambda so that during cleanup the
+        # re-imported new reference is updated.
+        self.addCleanup(lambda patch: setattr(unittest.mock, 'patch', patch),
+                        old_patch)
+
+        with patch.dict('sys.modules'):
+            del sys.modules['unittest.mock']
+
+            def trace(frame, event, arg):
+                return trace
+
+            sys.settrace(trace)
+            self.addCleanup(sys.settrace, None)
+
+            from unittest.mock import (
+                Mock, MagicMock, NonCallableMock, NonCallableMagicMock
+            )
+
+            mocks = [
+                Mock, MagicMock, NonCallableMock, NonCallableMagicMock
+            ]
+
+            for mock in mocks:
+                obj = mock(spec=Something)
+                self.assertIsInstance(obj, Something)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2019-04-11-22-11-24.bpo-36598.hfzDUl.rst b/Misc/NEWS.d/next/Library/2019-04-11-22-11-24.bpo-36598.hfzDUl.rst
new file mode 100644
index 000000000000..2a7980209136
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-04-11-22-11-24.bpo-36598.hfzDUl.rst
@@ -0,0 +1,2 @@
+Fix ``isinstance`` check for Mock objects with spec when the code is
+executed under tracing. Patch by Karthikeyan Singaravelan.