Improve abc module and builtin function decorators (with ParamSpec) #5682
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* Make classmethod and staticmethod generic over the function. * abstractclassmethod and abstractstaticmethod are classes, not functions. * Remove mypy-specific comments.
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stdlib/builtins.pyi
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| def __init__(self, f: Callable[..., Any]) -> None: ... | ||
| def __init__(self, f: _FuncT) -> None: ... | ||
| def __new__(cls: Type[_T], *args: Any, **kwargs: Any) -> _T: ... | ||
| def __get__(self, obj: _T, type: Optional[Type[_T]] = ...) -> Callable[..., Any]: ... | ||
| def __get__(self, obj: _T, type: Type[_T] | None = ...) -> _FuncT: ... |
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This doesn't seem right, because the callable returned from __get__ doesn't take the class as a first argument.
>>> class Foo:
... @classmethod
... def bar(cls):
... print("Bar runs:", cls)
...
>>> Foo.bar()
Bar runs: <class '__main__.Foo'>
>>> Foo.__dict__['bar'].__func__(Foo)
Bar runs: <class '__main__.Foo'>Here Foo.__dict__['bar'] is the classmethod object, and for Foo.bar, its __get__ method gets called. The result is a bound method, which basically means that it includes the class similarly to partial:
>>> Foo.bar == Foo.__dict__['bar'].__get__(Foo(), None)
True
>>> Foo.bar
<bound method Foo.bar of <class '__main__.Foo'>>There was a problem hiding this comment.
Another problem: I think it calls __get__(None, Foo) when looking up Foo.bar, so None should be allowed for the first argument to __get__.
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Good catch. I tried to express this using ParamSpec, but I'm not sure this is correct. Also, do you know in what circumstances the owner argument can be None or not set?
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It appears to be a technicality that doesn't really occur in practice: "Python’s own __getattribute__() implementation always passes in both arguments whether they are required or not." Docs
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It seems that mypy doesn't support |
srittau
added
the
status: deferred
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Diff from mypy_primer, showing the effect of this PR on open source code: freqtrade (https://github.com/freqtrade/freqtrade.git)
+ freqtrade/data/history/jsondatahandler.py:26: error: Signature of "ohlcv_get_available_data" incompatible with supertype "IDataHandler"
+ freqtrade/data/history/jsondatahandler.py:38: error: Signature of "ohlcv_get_pairs" incompatible with supertype "IDataHandler"
+ freqtrade/data/history/jsondatahandler.py:126: error: Signature of "trades_get_pairs" incompatible with supertype "IDataHandler"
+ freqtrade/data/history/hdf5datahandler.py:25: error: Signature of "ohlcv_get_available_data" incompatible with supertype "IDataHandler"
+ freqtrade/data/history/hdf5datahandler.py:37: error: Signature of "ohlcv_get_pairs" incompatible with supertype "IDataHandler"
+ freqtrade/data/history/hdf5datahandler.py:125: error: Signature of "trades_get_pairs" incompatible with supertype "IDataHandler"
graphql-core (https://github.com/graphql-python/graphql-core.git)
+ src/graphql/execution/execute.py:212: error: Incompatible types in assignment (expression has type "Callable[[Any], bool]", variable has type "Callable[[Arg(Any, 'value')], bool]")
pydantic (https://github.com/samuelcolvin/pydantic.git)
+ pydantic/class_validators.py:57: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:84: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:100: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:107: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:113: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:125: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:135: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/class_validators.py:328: error: Missing type parameters for generic type "classmethod" [type-arg]
+ pydantic/main.py:953: error: Missing type parameters for generic type "classmethod" [type-arg]
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| @@ -109,19 +113,19 @@ class object: | |||
| def __dir__(self) -> Iterable[str]: ... | |||
| def __init_subclass__(cls) -> None: ... | |||
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| class staticmethod(object): # Special, only valid as a decorator. | |||
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Nit: These comments should be deleted. They seem misleading and mypy-specific to me.
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It's starting to LGTM, but I'm concerned about the new errors in freqtrade. They seem to be coming from usual |
srittau
changed the title
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staticmethod and classmethod are now generic on master. Do we still need the abc.pyi changes? |
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Going to close this as stale for now to keep the list of open PRs manageable. If you're still interested in seeing this through, feel free to reopen or open a new PR. |
functions.