1cdef6f40a
this fixes two distinct mypy errors one where NamedTuple/dataclassees can't be defined locally https://github.com/python/mypy/issues/7281 which happens when you run mypy like mypy -p my.core on warm cache the second error is the core/types.py file shadowing the stdlib types module
77 lines
2.2 KiB
Python
77 lines
2.2 KiB
Python
from .common import assert_subpackage; assert_subpackage(__name__)
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import dataclasses as dcl
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import inspect
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from typing import TypeVar, Type, Any
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D = TypeVar('D')
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def _freeze_dataclass(Orig: Type[D]):
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ofields = [(f.name, f.type, f) for f in dcl.fields(Orig)]
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# extract properties along with their types
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props = list(inspect.getmembers(Orig, lambda o: isinstance(o, property)))
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pfields = [(name, inspect.signature(getattr(prop, 'fget')).return_annotation) for name, prop in props]
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# FIXME not sure about name?
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# NOTE: sadly passing bases=[Orig] won't work, python won't let us override properties with fields
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RRR = dcl.make_dataclass('RRR', fields=[*ofields, *pfields])
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# todo maybe even declare as slots?
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return props, RRR
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# todo need some decorator thingie?
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from typing import Generic
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class Freezer(Generic[D]):
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'''
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Some magic which converts dataclass properties into fields.
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It could be useful for better serialization, for performance, for using type as a schema.
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For now only supports dataclasses.
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'''
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def __init__(self, Orig: Type[D]) -> None:
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self.Orig = Orig
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self.props, self.Frozen = _freeze_dataclass(Orig)
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def freeze(self, value: D) -> D:
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pvalues = {name: getattr(value, name) for name, _ in self.props}
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return self.Frozen(**dcl.asdict(value), **pvalues)
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### tests
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# this needs to be defined here to prevent a mypy bug
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# see https://github.com/python/mypy/issues/7281
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@dcl.dataclass
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class _A:
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x: Any
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# TODO what about error handling?
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@property
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def typed(self) -> int:
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return self.x['an_int']
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@property
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def untyped(self):
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return self.x['an_any']
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def test_freezer() -> None:
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val = _A(x=dict(an_int=123, an_any=[1, 2, 3]))
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af = Freezer(_A)
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fval = af.freeze(val)
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fd = vars(fval)
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assert fd['typed'] == 123
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assert fd['untyped'] == [1, 2, 3]
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###
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# TODO shit. what to do with exceptions?
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# e.g. good testcase is date parsing issue. should def yield Exception in this case
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# fundamentally it should just be Exception aware, dunno
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#
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# TODO not entirely sure if best to use Frozen as the schema, or actually convert objects..
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# guess need to experiment and see
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