- Issue #18622: unittest.mock.mock_open().reset_mock would recurse infinitely.

Patch from Nicola Palumbo and Laurent De Buyst.

Lib/unittest/mock.py

@@ -523,8 +523,14 @@ class NonCallableMock(Base):
     side_effect = property(__get_side_effect, __set_side_effect)
 
 
-    def reset_mock(self):
+    def reset_mock(self, visited=None):
         "Restore the mock object to its initial state."
+        if visited is None:
+            visited = []
+        if id(self) in visited:
+            return
+        visited.append(id(self))
+
         self.called = False
         self.call_args = None
         self.call_count = 0
@@ -535,11 +541,11 @@ class NonCallableMock(Base):
         for child in self._mock_children.values():
             if isinstance(child, _SpecState):
                 continue
-            child.reset_mock()
+            child.reset_mock(visited)
 
         ret = self._mock_return_value
         if _is_instance_mock(ret) and ret is not self:
-            ret.reset_mock()
+            ret.reset_mock(visited)
 
 
     def configure_mock(self, **kwargs):

Lib/unittest/test/testmock/testmock.py

@@ -246,6 +246,9 @@ class MockTest(unittest.TestCase):
         # used to cause recursion
         mock.reset_mock()
 
+    def test_reset_mock_on_mock_open_issue_18622(self):
+        a = mock.mock_open()
+        a.reset_mock()
 
     def test_call(self):
         mock = Mock()

Misc/ACKS

@@ -1582,3 +1582,5 @@ Gennadiy Zlobin
 Doug Zongker
 Peter Åstrand
 Ignacio Rossi
+Laurent De Buyst
+Nicola Palumbo

Misc/NEWS

@@ -17,6 +17,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #18622: unittest.mock.mock_open().reset_mock would recurse infinitely.
+  Patch from Nicola Palumbo and Laurent De Buyst.
+
 - Issue #23661: unittest.mock side_effects can now be exceptions again. This
   was a regression vs Python 3.4. Patch from Ignacio Rossi