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import functools |
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import inspect |
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from ... import _class_placeholder |
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from ... import _pep_570_when |
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from .. import matchable |
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from ..patterns import mapping_match |
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from . import common |
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def _varargs(signature): |
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for parameter in signature.parameters.values(): |
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if parameter.kind is inspect.Parameter.VAR_POSITIONAL: |
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yield parameter |
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def _dispatch(func, matches, bound_args, bound_kwargs): |
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for key, value in matches.items(): |
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if key in bound_kwargs: |
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raise TypeError |
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bound_kwargs[key] = value |
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function_sig = inspect.signature(func) |
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function_args = function_sig.bind(**bound_kwargs) |
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for parameter in _varargs(function_sig): |
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function_args.arguments[parameter.name] = bound_args |
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function_args.apply_defaults() |
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return func(*function_args.args, **function_args.kwargs) |
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class Function(common.Descriptor): |
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"""Decorator with value-based dispatch. Acts as a function.""" |
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def __init__(self, func, *args, **kwargs): |
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del func |
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super().__init__(*args, **kwargs) |
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self.matchers = [] |
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def _matchers(self): |
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yield self.matchers |
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def __get__(self, instance, owner): |
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if instance is None: |
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return self |
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return functools.partial(self, instance) |
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def _bound_and_values(self, args, kwargs): |
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# Then we figure out what signature we're giving the outside world. |
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signature = inspect.signature(self) |
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# The signature lets us regularize the call and apply any defaults |
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bound_arguments = signature.bind(*args, **kwargs) |
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bound_arguments.apply_defaults() |
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# Extract the *args and **kwargs, if any. |
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# These are never used in the matching, just passed to the underlying function |
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bound_args = () |
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bound_kwargs = {} |
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values = bound_arguments.arguments.copy() |
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for parameter in signature.parameters.values(): |
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if parameter.kind is inspect.Parameter.VAR_POSITIONAL: |
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bound_args = values.pop(parameter.name) |
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if parameter.kind is inspect.Parameter.VAR_KEYWORD: |
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bound_kwargs = values.pop(parameter.name) |
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return bound_args, bound_kwargs, values |
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def __call__(*args, **kwargs): |
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# Okay, so, this is a convoluted mess. |
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# First, we extract self from the beginning of the argument list |
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self, *args = args |
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bound_args, bound_kwargs, values = self._bound_and_values(args, kwargs) |
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matchable_ = matchable.Matchable(values) |
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for structure, func in self.matchers: |
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if matchable_(structure): |
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return _dispatch(func, matchable_.matches, bound_args, bound_kwargs) |
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raise ValueError(values) |
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@_pep_570_when.pep_570_when |
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def when(self, kwargs): |
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"""Add a binding for this function.""" |
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return common.decorate(self.matchers, _placeholder_kwargs(kwargs)) |
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def _kwarg_structure(kwargs): |
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return mapping_match.DictPattern(kwargs, exhaustive=True) |
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def _placeholder_kwargs(kwargs): |
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if any(_class_placeholder.is_placeholder(kwarg) for kwarg in kwargs.values()): |
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@_class_placeholder.placeholder |
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def _placeholder(cls): |
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return _kwarg_structure( |
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{ |
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name: ( |
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kwarg(cls) |
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if _class_placeholder.is_placeholder(kwarg) |
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else kwarg |
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) |
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for (name, kwarg) in kwargs.items() |
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} |
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) |
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return _placeholder |
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return _kwarg_structure(kwargs) |
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mwchase /
python-structured-data
