gh-108682: [Enum] raise TypeError if super().__new__ called in custom __new__#108704
gh-108682: [Enum] raise TypeError if super().__new__ called in custom __new__#108704ethanfurman merged 6 commits intopython:mainfrom
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Thanks @ethanfurman for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12. |
…custom __new__ (pythonGH-108704) When overriding the `__new__` method of an enum, the underlying data type should be created directly; i.e. . member = object.__new__(cls) member = int.__new__(cls, value) member = str.__new__(cls, value) Calling `super().__new__()` finds the lookup version of `Enum.__new__`, and will now raise an exception when detected. (cherry picked from commit d48760b) Co-authored-by: Ethan Furman <ethan@stoneleaf.us>
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Sorry, @ethanfurman, I could not cleanly backport this to |
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GH-108733 is a backport of this pull request to the 3.12 branch. |
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… custom __new__ (GH-108704) (#108733) gh-108682: [Enum] raise TypeError if super().__new__ called in custom __new__ (GH-108704) When overriding the `__new__` method of an enum, the underlying data type should be created directly; i.e. . member = object.__new__(cls) member = int.__new__(cls, value) member = str.__new__(cls, value) Calling `super().__new__()` finds the lookup version of `Enum.__new__`, and will now raise an exception when detected. (cherry picked from commit d48760b) Co-authored-by: Ethan Furman <ethan@stoneleaf.us>
…custom __new__ (pythonGH-108704) When overriding the `__new__` method of an enum, the underlying data type should be created directly; i.e. . member = object.__new__(cls) member = int.__new__(cls, value) member = str.__new__(cls, value) Calling `super().__new__()` finds the lookup version of `Enum.__new__`, and will now raise an exception when detected. (cherry picked from commit d48760b)
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GH-108739 is a backport of this pull request to the 3.11 branch. |
… custom __new__ (GH-108704) (GH-108739) When overriding the `__new__` method of an enum, the underlying data type should be created directly; i.e. . member = object.__new__(cls) member = int.__new__(cls, value) member = str.__new__(cls, value) Calling `super().__new__()` finds the lookup version of `Enum.__new__`, and will now raise an exception when detected. (cherry picked from commit d48760b)
| # still not found -- verify that members exist, in-case somebody got here mistakenly | ||
| # (such as via super when trying to override __new__) | ||
| if not cls._member_map_: | ||
| raise TypeError("%r has no members defined" % cls) | ||
| # |
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Is it ok to move _member_map_ check after _missing_ hook?
I have a derived class has no members and hook _missing_, it raise exception here.
@ethanfurman
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Unfortunately, no. I tried to do that, but then the bug wasn't fixed.
What does your missing() hook do?
If you have no other alternative, you'll need to subclass EnumType and override the __call__ method.
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Thanks for the quick reply. here is an example:
from enum import Enum
class DynamicEnum(Enum):
@classmethod
def _missing_(cls, value):
temp = object.__new__(cls)
temp._name_ = f"{cls.__name__}_{value}"
temp._value_ = value
return temp
dynamic_enum = DynamicEnum(3)
print(dynamic_enum)
print(dynamic_enum.value)
which prints
DynamicEnum.DynamicEnum_3
3
before this change.
As my understanding, hook _missing_ handle the missing input, a dynamic value in the above case.
so I raise the question: hook _missing_ before empty check.
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I'll chime in here as well. I have the same question and got hit by this change as well. We have a setup where we do like:
from enum import Enum
class Result(Enum):
@classmethod
def _missing_(cls, value):
v = None
for subclass in cls.__subclasses__():
try:
v = subclass(value)
except:
pass
return v
class CommonResult(Result):
OK = 0
ERR_FOO = -0x1
ERR_BAR = -0x2
Previously, Result(0) returned CommonResult.OK. Now throws. It was a nifty pattern to use, and it sort of breaks the combination of using the _missing_ and subclasses of Enum.
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