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"""Common classes and functions for implementing dynamic matchers.""" |
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from __future__ import annotations |
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import functools |
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import typing |
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from ... import _class_placeholder |
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from ..._adt import prewritten_methods |
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from .. import destructure |
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T = typing.TypeVar("T") # pylint: disable=invalid-name |
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Matcher = typing.Union[T, _class_placeholder.Placeholder[T]] |
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def _apply(structure: Matcher[T], base: typing.Optional[type]) -> T: |
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if isinstance(structure, _class_placeholder.Placeholder): |
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# The cast is safe because we do the abstract check higher up |
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new = structure.func(typing.cast(type, base)) |
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_check_structure(new) |
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return new |
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non_placeholder = typing.cast(T, structure) |
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_check_structure(non_placeholder) |
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return non_placeholder |
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class MatchTemplate(typing.Generic[T]): |
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"""The core data type for managing dynamic matching functions.""" |
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def __init__(self) -> None: |
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self._templates: typing.List[typing.Tuple[Matcher[T], typing.Callable]] = [] |
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self._abstract = False |
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self._cache: typing.Dict[ |
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typing.Optional[type], typing.List[typing.Tuple[T, typing.Callable]] |
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] = {} |
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def copy_into(self, other: MatchTemplate[T]) -> None: |
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"""Given another template, copy this one's contents into it.""" |
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for structure, func in self._templates: |
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other.add_structure(structure, func) |
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# @property |
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# def abstract(self): |
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# return self._abstract |
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def add_structure(self, structure: Matcher[T], func: typing.Callable) -> None: |
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"""Add the given structure and function to the match template.""" |
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self._templates.append((structure, func)) |
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if isinstance(structure, _class_placeholder.Placeholder): |
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self._abstract = True |
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self._cache.pop(None, None) |
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for base, structures in self._cache.items(): |
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structures.append((_apply(structure, base), func)) |
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def _get_matchers( |
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self, base: type |
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) -> typing.List[typing.Tuple[T, typing.Callable]]: |
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if base in self._cache: |
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return self._cache[base] |
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return self._cache.setdefault( |
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base, |
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[(_apply(structure, base), func) for (structure, func) in self._templates], |
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) |
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def match_instance(self, matchable, instance) -> typing.Iterator[typing.Callable]: |
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"""Get the base associated with instance, if any, and match with it.""" |
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base = prewritten_methods.sum_base(instance) if self._abstract else None |
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yield from self.match(matchable, base) |
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def match(self, matchable, base) -> typing.Iterator[typing.Callable]: |
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"""If there is a match in the context of base, yield implementation.""" |
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if base is None and self._abstract: |
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raise ValueError |
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for structure, func in self._get_matchers(base): |
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if matchable(structure): |
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break |
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else: |
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return |
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# https://github.com/PyCQA/pylint/issues/1175 |
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yield func # pylint: disable=undefined-loop-variable |
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def _check_structure(structure) -> None: |
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destructure.names(structure) # Raise ValueError if there are duplicates |
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def decorate(matchers: MatchTemplate[T], structure: Matcher[T]): |
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"""Create a function decorator using the given structure, MatchTemplate.""" |
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def decorator(func: typing.Callable) -> typing.Callable: |
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matchers.add_structure(structure, func) |
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return func |
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return decorator |
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class Descriptor: |
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"""Base class for decorator classes.""" |
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__wrapped__: typing.Optional[typing.Callable] = None |
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__name__: typing.Optional[str] = None |
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104
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def __new__(cls, func: typing.Optional[typing.Callable]) -> Descriptor: |
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new = super().__new__(cls) |
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new.__doc__ = None |
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if func is None: |
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return new |
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return typing.cast(Descriptor, functools.wraps(func)(new)) |
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111
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def __set_name__(self, owner: type, name: str) -> None: |
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vars(self).setdefault("__name__", name) |
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114
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115
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SENTINEL = object() |
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def owns(descriptor: Descriptor, owner: type) -> bool: |
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"""Return whether the given class owns the given descriptor.""" |
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name = descriptor.__name__ |
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if name is None: |
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return False |
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return vars(owner).get(name, SENTINEL) is descriptor |
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mwchase /
python-structured-data
