From 819dc5793c2d603692bffa5a9a3011916f46463f Mon Sep 17 00:00:00 2001 From: Kumar Aditya Date: Thu, 18 Dec 2025 12:16:04 +0530 Subject: [PATCH] use NonCallableMock._lock for thread safety of call_count --- Lib/unittest/mock.py | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py index 34fd49bf56fbb6..64a01a0b713c61 100644 --- a/Lib/unittest/mock.py +++ b/Lib/unittest/mock.py @@ -1184,10 +1184,16 @@ def _increment_mock_call(self, /, *args, **kwargs): # handle call_args # needs to be set here so assertions on call arguments pass before # execution in the case of awaited calls - _call = _Call((args, kwargs), two=True) - self.call_args = _call - self.call_args_list.append(_call) - self.call_count = len(self.call_args_list) + with NonCallableMock._lock: + # Lock is used here so that call_args_list and call_count are + # set atomically otherwise it is possible that by the time call_count + # is set another thread may have appended to call_args_list. + # The rest of this function relies on list.append being atomic and + # skips locking. + _call = _Call((args, kwargs), two=True) + self.call_args = _call + self.call_args_list.append(_call) + self.call_count = len(self.call_args_list) # initial stuff for method_calls: do_method_calls = self._mock_parent is not None