10000 gh-111874: Call `__set_name__` on objects that define the method inside a `typing.NamedTuple` class dictionary as part of the creation of that class by AlexWaygood · Pull Request #111876 · python/cpython · GitHub
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gh-111874: Call __set_name__ on objects that define the method insid 8000 e a typing.NamedTuple class dictionary as part of the creation of that class #111876

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Merged
merged 17 commits into from
Nov 27, 2023
Merged

gh-111874: Call __set_name__ on objects that define the method inside a typing.NamedTuple class dictionary as part of the creation of that class #111876

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e3b703d
gh-111874: Call `__set_name__` on objects that define the method insi…
AlexWaygood Nov 9, 2023
f053310
fixup news
AlexWaygood Nov 9, 2023
7ccff63
Also add a test for TypedDict classes
AlexWaygood Nov 9, 2023
0d13e83
Merge branch 'namedtuple-setname' of https://github.com/AlexWaygood/c…
AlexWaygood Nov 9, 2023
e4e968a
Revert "Also add a test for TypedDict classes"
AlexWaygood Nov 9, 2023
e0c88f0
Exception -> BaseException
AlexWaygood Nov 13, 2023
d8102fd
Address review (and fix bug)
AlexWaygood Nov 16, 2023
f2a57b2
Update Lib/test/test_typing.py
AlexWaygood Nov 17, 2023
1909fd5
Handle strange exceptions raised on attempting to access `__set_name__`
AlexWaygood Nov 17, 2023
ed53fcb
typo
AlexWaygood Nov 17, 2023
c2c65c6
big comment
AlexWaygood Nov 17, 2023
e79ea37
Revert "big comment"
AlexWaygood Nov 27, 2023
9fd8b6b
Revert "typo"
AlexWaygood Nov 27, 2023
fdab495
Revert "Handle strange exceptions raised on attempting to access `__s…
AlexWaygood Nov 27, 2023
3932d48
Add a test that asserts the correct behaviour
AlexWaygood Nov 27, 2023
3359ff6
Address Serhiy's second review pass
AlexWaygood Nov 27, 2023
ef628da
Merge branch 'main' into namedtuple-setname
AlexWaygood Nov 27, 2023
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77 changes: 77 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7535,6 +7535,83 @@ class GenericNamedTuple(NamedTuple, Generic[T]):

self.assertEqual(CallNamedTuple.__orig_bases__, (NamedTuple,))

def test_setname_called_on_values_in_class_dictionary(self):
class Vanilla:
def __set_name__(self, owner, name):
self.name = name

class Foo(NamedTuple):
attr = Vanilla()

foo = Foo()
self.assertEqual(len(foo), 0)
self.assertNotIn('attr', Foo._fields)
self.assertIsInstance(foo.attr, Vanilla)
self.assertEqual(foo.attr.name, "attr")

class Bar(NamedTuple):
attr: Vanilla = Vanilla()

bar = Bar()
self.assertEqual(len(bar), 1)
self.assertIn('attr', Bar._fields)
self.assertIsInstance(bar.attr, Vanilla)
self.assertEqual(bar.attr.name, "attr")

def test_setname_raises_the_same_as_on_other_classes(self):
class CustomException(BaseException): pass

class Annoying:
def __set_name__(self, owner, name):
raise CustomException

annoying = Annoying()

with self.assertRaises(CustomException) as cm:
class NormalClass:
attr = annoying
normal_exception = cm.exception

with self.assertRaises(CustomException) as cm:
class NamedTupleClass(NamedTuple):
attr = annoying
namedtuple_exception = cm.exception

self.assertIs(type(namedtuple_exception), CustomException)
self.assertIs(type(namedtuple_exception), type(normal_exception))

self.assertEqual(len(namedtuple_exception.__notes__), 1)
self.assertEqual(
len(namedtuple_exception.__notes__), len(normal_exception.__notes__)
)

expected_note = (
"Error calling __set_name__ on 'Annoying' instance "
"'attr' in 'NamedTupleClass'"
)
self.assertEqual(namedtuple_exception.__notes__[0], expected_note)
self.assertEqual(
namedtuple_exception.__notes__[0],
normal_exception.__notes__[0].replace("NormalClass", "NamedTupleClass")
)

def test_strange_errors_when_accessing_set_name_itself(self):
class CustomException(Exception): pass

class Meta(type):
def __getattribute__(self, attr):
if attr == "__set_name__":
raise CustomException
return object.__getattribute__(self, attr)

class VeryAnnoying(metaclass=Meta): pass

very_annoying = VeryAnnoying()

with self.assertRaises(CustomException):
class Foo(NamedTuple):
attr = very_annoying


class TypedDictTests(BaseTestCase):
def test_basics_functional_syntax(self):
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21 changes: 18 additions & 3 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2743,11 +2743,26 @@ def __new__(cls, typename, bases, ns):
class_getitem = _generic_class_getitem
nm_tpl.__class_getitem__ = classmethod(class_getitem)
# update from user namespace without overriding special namedtuple attributes
for key in ns:
for key, val in ns.items():
if key in _prohibited:
raise AttributeError("Cannot overwrite NamedTuple attribute " + key)
elif key not in _special and key not in nm_tpl._fields:
setattr(nm_tpl, key, ns[key])
elif key not in _special:
if key not in nm_tpl._fields:
setattr(nm_tpl, key, val)
try:
set_name = type(val).__set_name__
except AttributeError:
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Is it worth adding a test for the case where this yields some other exception (e.g. due to a weird metaclass)?

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@AlexWaygood AlexWaygood Nov 17, 2023 •
edited
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Good catch. Seems like for normal classes, if any strange exception is raised when trying to lookup __set_name__, the interpreter just swallows it and moves on:

>>> class Meta(type):
...     def __getattribute__(self, attr):
...         if attr == "__set_name__":
...             raise BaseException("NO")
...
>>> class VeryAnnoying(metaclass=Meta): pass
...
>>> class Foo:
...     attr = VeryAnnoying()
...
>>>

We should do the same here (though I don't want to swallow BaseExceptions, since that would catch KeyboardInterrupt, SystemExit, etc. -- I think I'll just use except Exception).

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Addressed in 1909fd5

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Seems like for normal classes, if any strange exception is raised when trying to lookup __set_name__, the interpreter just swallows it and moves on:

It looks like a bug. I do not think it should be reproduced here. It is better to fix it for normal classes.

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Okay, I opened #112453, and will revert the changes made here that reproduce the bug

pass
else:
try:
set_name(val, nm_tpl, key)
except BaseException as e:
e.add_note(
f"Error calling __set_name__ on {type(val).__name__!r} "
f"instance {key!r} in {typename!r}"
)
raise

if Generic in bases:
nm_tpl.__init_subclass__()
return nm_tpl
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2023-11-09-11-07-34.gh-issue-111874.dzYc3j.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
When creating a :class:`typing.NamedTuple` class, ensure
:func:`~object.__set_name__` is called on all objects that define
``__set_name__`` and exist in the values of the ``NamedTuple`` class's class
dictionary. Patch by Alex Waygood.
0