bpo-45156: Fixes inifite loop on unittest.mock.seal() (GH-28300)

Fixes infinite loop on unittest.mock.seal() of mocks created by
unittest.create_autospec().

Co-authored-by: Dong-hee Na <donghee.na92@gmail.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 8193efc..9f99a5a 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -1005,6 +1005,11 @@ class NonCallableMock(Base):
         if _new_name in self.__dict__['_spec_asyncs']:
             return AsyncMock(**kw)
 
+        if self._mock_sealed:
+            attribute = f".{kw['name']}" if "name" in kw else "()"
+            mock_name = self._extract_mock_name() + attribute
+            raise AttributeError(mock_name)
+
         _type = type(self)
         if issubclass(_type, MagicMock) and _new_name in _async_method_magics:
             # Any asynchronous magic becomes an AsyncMock
@@ -1023,12 +1028,6 @@ class NonCallableMock(Base):
                 klass = Mock
         else:
             klass = _type.__mro__[1]
-
-        if self._mock_sealed:
-            attribute = "." + kw["name"] if "name" in kw else "()"
-            mock_name = self._extract_mock_name() + attribute
-            raise AttributeError(mock_name)
-
         return klass(**kw)
 
 
@@ -2913,6 +2912,8 @@ def seal(mock):
             continue
         if not isinstance(m, NonCallableMock):
             continue
+        if isinstance(m._mock_children.get(attr), _SpecState):
+            continue
         if m._mock_new_parent is mock:
             seal(m)