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62 lines
2.4 KiB
Python
62 lines
2.4 KiB
Python
# Released under the MIT License. See LICENSE for details.
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#
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"""Functionality for importing, exporting, and validating dataclasses.
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This allows complex nested dataclasses to be flattened to json-compatible
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data and restored from said data. It also gracefully handles and preserves
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unrecognized attribute data, allowing older clients to interact with newer
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data formats in a nondestructive manner.
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"""
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from __future__ import annotations
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import dataclasses
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from typing import TYPE_CHECKING
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from efro.dataclassio._base import _parse_annotated, _get_origin
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from efro.dataclassio._prep import PrepSession
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if TYPE_CHECKING:
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from typing import Any, Dict, Type, Tuple, Optional, List, Set
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class FieldStoragePathCapture:
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"""Utility for obtaining dataclass storage paths in a type safe way.
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Given dataclass instance foo, FieldStoragePathCapture(foo).bar.eep
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will return 'bar.eep' (or something like 'b.e' if storagenames are
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overridden). This can be combined with type-checking tricks that
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return foo in the type-checker's eyes while returning
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FieldStoragePathCapture(foo) at runtime in order to grant a measure
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of type safety to specifying field paths for things such as db
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queries. Be aware, however, that the type-checker will incorrectly
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think these lookups are returning actual attr values when they
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are actually returning strings.
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"""
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def __init__(self, obj: Any, path: List[str] = None):
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if path is None:
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path = []
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if not dataclasses.is_dataclass(obj):
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raise TypeError(f'Expected a dataclass type/instance;'
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f' got {type(obj)}.')
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self._cls = obj if isinstance(obj, type) else type(obj)
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self._path = path
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def __getattr__(self, name: str) -> Any:
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prep = PrepSession(explicit=False).prep_dataclass(self._cls,
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recursion_level=0)
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try:
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anntype = prep.annotations[name]
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except KeyError as exc:
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raise AttributeError(f'{type(self)} has no {name} field.') from exc
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anntype, ioattrs = _parse_annotated(anntype)
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storagename = (name if (ioattrs is None or ioattrs.storagename is None)
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else ioattrs.storagename)
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origin = _get_origin(anntype)
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path = self._path + [storagename]
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if dataclasses.is_dataclass(origin):
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return FieldStoragePathCapture(origin, path=path)
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return '.'.join(path)
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