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a7c25bb01f
for most of our data classes we can use dataclasses.dataclass with frozen=True or even plain named tuples. the TOC structure we'll need to generate proper navigation links is most easily represented and used as a cyclic structure though, and for that we can use neither. if we want to make the TOC structures immutable (which seems like a good idea) we'll need a hack of *some* kind, and this hack seems like the least intrusive.
21 lines
923 B
Python
21 lines
923 B
Python
from typing import Any
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_frozen_classes: dict[type, type] = {}
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# make a derived class freezable (ie, disallow modifications).
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# we do this by changing the class of an instance at runtime when freeze()
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# is called, providing a derived class that is exactly the same except
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# for a __setattr__ that raises an error when called. this beats having
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# a field for frozenness and an unconditional __setattr__ that checks this
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# field because it does not insert anything into the class dict.
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class Freezeable:
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def freeze(self) -> None:
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cls = type(self)
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if not (frozen := _frozen_classes.get(cls)):
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def __setattr__(instance: Any, n: str, v: Any) -> None:
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raise TypeError(f'{cls.__name__} is frozen')
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frozen = type(cls.__name__, (cls,), {
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'__setattr__': __setattr__,
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})
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_frozen_classes[cls] = frozen
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self.__class__ = frozen
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