bpo-43478: Restrict use of Mock objects as specs (GH-25326)
* Restrict using Mock objects as specs as this is always a test bug where the resulting mock is misleadingly useless.
* Skip a broken test that exposes a bug elsewhere in mock (noted in the original issue).
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 720f682..c606715 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -36,6 +36,10 @@
from functools import wraps, partial
+class InvalidSpecError(Exception):
+ """Indicates that an invalid value was used as a mock spec."""
+
+
_builtins = {name for name in dir(builtins) if not name.startswith('_')}
FILTER_DIR = True
@@ -653,10 +657,17 @@ def __getattr__(self, name):
self._mock_children[name] = result
elif isinstance(result, _SpecState):
- result = create_autospec(
- result.spec, result.spec_set, result.instance,
- result.parent, result.name
- )
+ try:
+ result = create_autospec(
+ result.spec, result.spec_set, result.instance,
+ result.parent, result.name
+ )
+ except InvalidSpecError:
+ target_name = self.__dict__['_mock_name'] or self
+ raise InvalidSpecError(
+ f'Cannot autospec attr {name!r} from target '
+ f'{target_name!r} as it has already been mocked out. '
+ f'[target={self!r}, attr={result.spec!r}]')
self._mock_children[name] = result
return result
@@ -1273,6 +1284,14 @@ def __init__(
)
if not unsafe:
_check_spec_arg_typos(kwargs)
+ if _is_instance_mock(spec):
+ raise InvalidSpecError(
+ f'Cannot spec attr {attribute!r} as the spec '
+ f'has already been mocked out. [spec={spec!r}]')
+ if _is_instance_mock(spec_set):
+ raise InvalidSpecError(
+ f'Cannot spec attr {attribute!r} as the spec_set '
+ f'target has already been mocked out. [spec_set={spec_set!r}]')
self.getter = getter
self.attribute = attribute
@@ -1500,6 +1519,18 @@ def __enter__(self):
if autospec is True:
autospec = original
+ if _is_instance_mock(self.target):
+ raise InvalidSpecError(
+ f'Cannot autospec attr {self.attribute!r} as the patch '
+ f'target has already been mocked out. '
+ f'[target={self.target!r}, attr={autospec!r}]')
+ if _is_instance_mock(autospec):
+ target_name = getattr(self.target, '__name__', self.target)
+ raise InvalidSpecError(
+ f'Cannot autospec attr {self.attribute!r} from target '
+ f'{target_name!r} as it has already been mocked out. '
+ f'[target={self.target!r}, attr={autospec!r}]')
+
new = create_autospec(autospec, spec_set=spec_set,
_name=self.attribute, **kwargs)
elif kwargs:
@@ -2613,6 +2644,9 @@ def create_autospec(spec, spec_set=False, instance=False, _parent=None,
spec = type(spec)
is_type = isinstance(spec, type)
+ if _is_instance_mock(spec):
+ raise InvalidSpecError(f'Cannot autospec a Mock object. '
+ f'[object={spec!r}]')
is_async_func = _is_async_func(spec)
_kwargs = {'spec': spec}
if spec_set: