Use EnumMeta instead of Enum to mark enum classes #4319
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elazarg
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| main:7: error: Incompatible types in assignment (expression has type "int", variable has type "Medal") | ||
| m = 1 # E: Incompatible types in assignment (expression has type "int", variable has type "Medal") | ||
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| [case testEnumFromEnumMetaBasics] |
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I think it would be helpful to have a testcase for something that inherits from a class that has EnumMeta as a metaclass, to check those classes are still found to be Enums for all intents and purposes.
Also perhaps a test of a EnumMeta deriving class that tries to use generics?
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I think it would be helpful to have a testcase for something that inherits from a class that has EnumMeta as a metaclass, to check those classes are still found to be Enums for all intents and purposes.
Will do, but note that this is already handled by classes that inherit Enum itself.
I'm not sure I understand the second suggestion. Should mypy support something like that?
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Good point on the first, but just to be safe. Also on the second, I mean to check that it fails correctly :)
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Hm, I think you need to |
elazarg
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test-data/unit/check-enum.test
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| bronze = None | ||
| reveal_type(Medal.bronze) # E: Revealed type is '__main__.Medal' | ||
| m = Medal.gold | ||
| m = 1 # E: Incompatible types inassignment (expression has type "int", variable has type "Medal") |
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Needs a space between "in" and "assignment"
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Yep. Sorry about that.
elazarg
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mypy/semanal.py
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| @@ -1275,6 +1273,11 @@ def analyze_metaclass(self, defn: ClassDef) -> None: | |||
| # do not declare explicit metaclass, but it's harder to catch at this stage | |||
| if defn.metaclass is not None: | |||
| self.fail("Inconsistent metaclass structure for '%s'" % defn.name, defn) | |||
| else: | |||
| if defn.info.metaclass_type.type.fullname() == 'enum.EnumMeta': | |||
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So if the metaclass is a subclass of EnumMeta, it's not an enum? (I'm not sure I care, but I wonder if this is an intentional choice.)
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| [case testEnumFromEnumMetaBasics] | ||
| from enum import EnumMeta | ||
| class Medal(metaclass=EnumMeta): |
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This code doesn't actually work -- you need to also inherit from enum.Enum, else the class definition fails at runtime with
TypeError: Medal().__init__() takes no arguments
(Note: I'm not asking that mypy enforce this -- but I still think the test should work as an example.)
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I'm not sure what to do about it. If Medal inherits from Enum, the test doesn't check for what I want it to check. We might as well drop it.
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I can add a def __init__(self, *args): pass constructor, if you deem it better. It works, though might be considered an implementation detail.
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I'd say add a comment explaining that it doesn't work at runtime and what you are testing for.
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| [case testEnumFromEnumMetaSubclass] | ||
| from enum import EnumMeta | ||
| class Achievement(metaclass=EnumMeta): pass |
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This must also inherit from enum.Enum.
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This seems to have broken typeshed CI. https://travis-ci.org/python/typeshed/jobs/364931878 I'll look into it now. |
This fixes an error in Travis that seems to have been caused by python/mypy#4319. The fix was taken from the stdlib/3.4/enum.pyi stub. Mypy no longer assumes that classes whose metaclass is EnumMeta are subclasses of Enum, so we can't bound the typevar on Enum.
This fixes an error in Travis that seems to have been caused by python/mypy#4319. The fix was taken from the stdlib/3.4/enum.pyi stub. Mypy no longer assumes that classes whose metaclass is EnumMeta are subclasses of Enum, so we can't bound the typevar on Enum.
This fixes an error in Travis that seems to have been caused by python/mypy#4319. The fix was taken from the stdlib/3.4/enum.pyi stub. Mypy no longer assumes that classes whose metaclass is EnumMeta are subclasses of Enum, so we can't bound the typevar on Enum.
This fixes an error in Travis that seems to have been caused by python/mypy#4319. The fix was taken from the stdlib/3.4/enum.pyi stub. Mypy no longer assumes that classes whose metaclass is EnumMeta are subclasses of Enum, so we can't bound the typevar on Enum.
Implement #4311.
The tests will fail until python/typeshed#1770 is synched.