64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
from __future__ import annotations
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from abc import ABC, abstractmethod
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from typing import Generic, TypeVar, Iterable, cast
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from typing_extensions import override
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T = TypeVar("T")
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class LazyProxy(Generic[T], ABC):
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"""Implements data methods to pretend that an instance is another instance.
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This includes forwarding attribute access and other methods.
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"""
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# Note: we have to special case proxies that themselves return proxies
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# to support using a proxy as a catch-all for any random access, e.g. `proxy.foo.bar.baz`
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def __getattr__(self, attr: str) -> object:
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proxied = self.__get_proxied__()
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if isinstance(proxied, LazyProxy):
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return proxied # pyright: ignore
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return getattr(proxied, attr)
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@override
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def __repr__(self) -> str:
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proxied = self.__get_proxied__()
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if isinstance(proxied, LazyProxy):
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return proxied.__class__.__name__
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return repr(self.__get_proxied__())
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@override
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def __str__(self) -> str:
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proxied = self.__get_proxied__()
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if isinstance(proxied, LazyProxy):
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return proxied.__class__.__name__
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return str(proxied)
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@override
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def __dir__(self) -> Iterable[str]:
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proxied = self.__get_proxied__()
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if isinstance(proxied, LazyProxy):
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return []
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return proxied.__dir__()
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@property # type: ignore
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@override
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def __class__(self) -> type: # pyright: ignore
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proxied = self.__get_proxied__()
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if issubclass(type(proxied), LazyProxy):
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return type(proxied)
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return proxied.__class__
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def __get_proxied__(self) -> T:
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return self.__load__()
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def __as_proxied__(self) -> T:
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"""Helper method that returns the current proxy, typed as the loaded object"""
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return cast(T, self)
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@abstractmethod
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def __load__(self) -> T:
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...
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