10000 gh-104555: Runtime-checkable protocols: Don't let previous calls to `isinstance()` influence whether `issubclass()` raises an exception by AlexWaygood · Pull Request #104559 · python/cpython · GitHub
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gh-104555: Runtime-checkable protocols: Don't let previous calls to isinstance() influence whether issubclass() raises an exception #104559

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Merged
merged 12 commits into from
May 17, 2023
Merged

gh-104555: Runtime-checkable protocols: Don't let previous calls to isinstance() influence whether issubclass() raises an exception #104559

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2601138
gh-104555: Sidestep the ABCMeta.__instancecheck__ cache in typing._Pr…
AlexWaygood May 16, 2023
f3a4551
Simplify test
AlexWaygood May 16, 2023
714badc
Optimise
AlexWaygood May 16, 2023
04ed974
who needs codespell when we have carl
AlexWaygood May 16, 2023
9c5c75f
Merge branch 'fix-runtime-protocols' of https://github.com/AlexWaygoo…
AlexWaygood May 16, 2023
49373a9
be more careful
AlexWaygood May 16, 2023
e114fe9
Add comment
AlexWaygood May 16, 2023
b5cc9cd
Add more failing tests (thanks sunmy2019!)
AlexWaygood May 17, 2023
5f72b82
Better fix
AlexWaygood May 17, 2023
bb56e13
Improve comments
AlexWaygood May 17, 2023
430cacd
📜🤖 Added by blurb_it.
blurb-it[bot] May 17, 2023
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Apply suggestions from code review
AlexWaygood May 17, 2023
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@AlexWaygood
AlexWaygood committed May 17, 2023
commit 5f72b820e68c63c44c51f6c7f7f068e6cfab57c2
31 changes: 15 additions & 16 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1775,8 +1775,8 @@ def _pickle_pskwargs(pskwargs):


class _ProtocolMeta(ABCMeta):
# This metaclass is really unfortunate and exists only because of
# the lack of __instancehook__.
# This metaclass is somewhat unfortunate,
# but is necessary for several reasons...
def __init__(cls, *args, **kwargs):
super().__init__(*args, **kwargs)
cls.__protocol_attrs__ = _get_protocol_attrs(cls)
Expand All @@ -1786,6 +1786,17 @@ def __init__(cls, *args, **kwargs):
callable(getattr(cls, attr, None)) for attr in cls.__protocol_attrs__
)

def __subclasscheck__(cls, other):
if (
getattr(cls, '_is_protocol', False)
and not cls.__callable_proto_members_only__
and not _allow_reckless_class_checks(depth=2)
):
raise TypeError(
"Protocols with non-method members don't support issubclass()"
)
return super().__subclasscheck__(other)

def __instancecheck__(cls, instance):
# We need this method for situations where attributes are
# assigned in __init__.
Expand All @@ -1798,17 +1809,10 @@ def __instancecheck__(cls, instance):
raise TypeError("Instance and class checks can only be used with"
" @runtime_checkable protocols")

# gh-104555: Don't call super().__instancecheck__ here,
# ABCMeta.__instancecheck__ would erroneously use it to populate the cache,
# which would cause incorrect results for *issubclass()* calls
if type.__instancecheck__(cls, instance):
if super().__instancecheck__(instance):
return True

if is_protocol_cls:
# Fast path for protocols with only callable members
if cls.__callable_proto_members_only__ and issubclass(type(instance), cls):
return True

getattr_static = _lazy_load_getattr_static()
for attr in cls.__protocol_attrs__:
try:
Expand All @@ -1820,7 +1824,7 @@ def __instancecheck__(cls, instance):
else:
return True

return super().__instancecheck__(instance)
return False


class Protocol(Generic, metaclass=_ProtocolMeta):
Expand Down Expand Up @@ -1876,11 +1880,6 @@ def _proto_hook(other):
raise TypeError("Instance and class checks can only be used with"
" @runtime_checkable protocols")

if not cls.__callable_proto_members_only__ :
if _allow_reckless_class_checks():
return NotImplemented
raise TypeError("Protocols with non-method members"
" don't support issubclass()")
if not isinstance(other, type):
# Same error message as for issubclass(1, int).
raise TypeError('issubclass() arg 1 must be a class')
Expand Down
0