From 830b43d03cc47a27a22a50d777f23c8e60820867 Mon Sep 17 00:00:00 2001
From: Xtreak <tir.karthi@gmail.com>
Date: Sun, 14 Apr 2019 00:42:33 +0530
Subject: [PATCH] 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 .
---
 Lib/unittest/mock.py                          |  2 +-
 Lib/unittest/test/testmock/testmock.py        | 38 +++++++++++++++++++
 .../2019-04-11-22-11-24.bpo-36598.hfzDUl.rst  |  2 +
 3 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2019-04-11-22-11-24.bpo-36598.hfzDUl.rst

diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 8684f1dfa57..0e77f0e4894 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -739,7 +739,7 @@ class NonCallableMock(Base):
 
         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 66a5720d143..37f14c37f47 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1847,6 +1847,44 @@ class MockTest(unittest.TestCase):
         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 00000000000..2a798020913
--- /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.