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"""Utilities for destructuring values using matchables and match targets. |
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Given a value to destructure, called ``value``: |
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- Construct a matchable: ``matchable = Matchable(value)`` |
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- The matchable is initially falsy, but it will become truthy if it is passed a |
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**match target** that matches ``value``: |
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``assert matchable(some_pattern_that_matches)`` (Matchable returns itself |
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from the call, so you can put the calls in an if-elif block, and only make a |
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given call at most once.) |
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- When the matchable is truthy, it can be indexed to access bindings created by |
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the target. |
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""" |
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from __future__ import annotations |
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import inspect |
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from . import _attribute_constructor |
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from . import _descriptor |
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from ._descriptor import Property |
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from ._destructure import names |
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from ._match_dict import MatchDict |
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from ._matchable import Matchable |
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from ._patterns.basic_patterns import Pattern |
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from ._patterns.bind import Bind |
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from ._patterns.mapping_match import AttrPattern |
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from ._patterns.mapping_match import DictPattern |
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# In lower-case for aesthetics. |
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pat = _attribute_constructor.AttributeConstructor( # pylint: disable=invalid-name |
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Pattern |
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) |
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def _make_args_positional(func, positional_until): |
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signature = inspect.signature(func) |
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new_parameters = [] |
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for index, parameter in enumerate(signature.parameters.values()): |
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if positional_until and parameter.kind is inspect.Parameter.POSITIONAL_ONLY: |
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raise ValueError("Signature already contains positional-only arguments") |
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if index < positional_until: |
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if parameter.kind is not inspect.Parameter.POSITIONAL_OR_KEYWORD: |
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raise ValueError("Cannot overwrite non-POSITIONAL_OR_KEYWORD kind") |
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parameter = parameter.replace(kind=inspect.Parameter.POSITIONAL_ONLY) |
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new_parameters.append(parameter) |
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new_signature = signature.replace(parameters=new_parameters) |
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if new_signature != signature: |
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func.__signature__ = new_signature |
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# This wraps a function that, for reasons, can't be called directly by the code |
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# The function body should probably just be a docstring. |
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def function(_func=None, *, positional_until=0): |
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"""Convert a function to dispatch by value. |
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The original function is not called when the dispatch function is invoked. |
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""" |
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def wrap(func): |
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_make_args_positional(func, positional_until) |
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return _descriptor.Function(func) |
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if _func is None: |
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return wrap |
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return wrap(_func) |
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def decorate_in_order(*args): |
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"""Apply decorators in the order they're passed to the function.""" |
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def decorator(func): |
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for arg in args: |
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func = arg(func) |
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return func |
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return decorator |
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__all__ = [ |
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"AttrPattern", |
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"Bind", |
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"DictPattern", |
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"MatchDict", |
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"Matchable", |
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"Pattern", |
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"Property", |
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"decorate_in_order", |
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"function", |
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"names", |
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"pat", |
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] |
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mwchase /
python-structured-data
