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import functools |
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import inspect |
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from . import _destructure |
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from . import _doc_wrapper |
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from . import _matchable |
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from . import _pep_570_when |
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from ._patterns import mapping_match |
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def _decorate(matchers, structure, func): |
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matchers.append((structure, func)) |
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return func |
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class Descriptor: |
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"""Base class for decorator classes.""" |
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__wrapped__ = None |
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def __new__(cls, func, *args, **kwargs): |
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new = super().__new__(cls, *args, **kwargs) |
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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 functools.wraps(func)(new) |
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@_doc_wrapper.DocWrapper.wrap_class |
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class Property(Descriptor): |
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"""Decorator with value-based dispatch. Acts as a property.""" |
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fset = None |
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fdel = None |
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protected = False |
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def __new__(cls, func=None, fset=None, fdel=None, doc=None, *args, **kwargs): |
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del fset, fdel, doc |
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return super().__new__(cls, func, *args, **kwargs) |
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def __init__(self, func=None, fset=None, fdel=None, doc=None, *args, **kwargs): |
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del func |
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super().__init__(*args, **kwargs) |
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self.fset = fset |
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self.fdel = fdel |
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if doc is not None: |
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self.__doc__ = doc |
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self.get_matchers = [] |
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self.set_matchers = [] |
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self.delete_matchers = [] |
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self.protected = True |
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def __setattr__(self, name, value): |
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if self.protected and name != "__doc__": |
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raise AttributeError |
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super().__setattr__(name, value) |
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def __delattr__(self, name): |
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if self.protected and name != "__doc__": |
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raise AttributeError |
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super().__delattr__(name) |
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def getter(self, getter): |
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"""Return a copy of self with the getter replaced.""" |
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new = Property(getter, self.fset, self.fdel, self.__doc__) |
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new.get_matchers.extend(self.get_matchers) |
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new.set_matchers.extend(self.set_matchers) |
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new.delete_matchers.extend(self.delete_matchers) |
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return new |
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def setter(self, setter): |
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"""Return a copy of self with the setter replaced.""" |
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new = Property(self.__wrapped__, setter, self.fdel, self.__doc__) |
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new.get_matchers.extend(self.get_matchers) |
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new.set_matchers.extend(self.set_matchers) |
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new.delete_matchers.extend(self.delete_matchers) |
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return new |
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def deleter(self, deleter): |
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"""Return a copy of self with the deleter replaced.""" |
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new = Property(self.__wrapped__, self.fset, deleter, self.__doc__) |
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new.get_matchers.extend(self.get_matchers) |
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new.set_matchers.extend(self.set_matchers) |
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new.delete_matchers.extend(self.delete_matchers) |
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return new |
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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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matchable = _matchable.Matchable(instance) |
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for (structure, func) in self.get_matchers: |
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if matchable(structure): |
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return func(**matchable.matches) |
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if self.__wrapped__ is None: |
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raise ValueError(self) |
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return self.__wrapped__(instance) |
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def __set__(self, instance, value): |
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matchable = _matchable.Matchable((instance, value)) |
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for (structure, func) in self.set_matchers: |
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if matchable(structure): |
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func(**matchable.matches) |
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return |
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if self.fset is None: |
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raise ValueError((instance, value)) |
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self.fset(instance, value) |
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def __delete__(self, instance): |
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matchable = _matchable.Matchable(instance) |
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for (structure, func) in self.delete_matchers: |
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if matchable(structure): |
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func(**matchable.matches) |
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return |
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if self.fdel is None: |
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raise ValueError(instance) |
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self.fdel(instance) |
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def get_when(self, instance): |
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"""Add a binding to the getter.""" |
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structure = instance |
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_destructure.names(structure) # Raise ValueError if there are duplicates |
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return functools.partial(_decorate, self.get_matchers, structure) |
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def set_when(self, instance, value): |
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"""Add a binding to the setter.""" |
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structure = (instance, value) |
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_destructure.names(structure) # Raise ValueError if there are duplicates |
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return functools.partial(_decorate, self.set_matchers, structure) |
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def delete_when(self, instance): |
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"""Add a binding to the deleter.""" |
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structure = instance |
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_destructure.names(structure) # Raise ValueError if there are duplicates |
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return functools.partial(_decorate, self.delete_matchers, structure) |
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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(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 __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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structure = mapping_match.DictPattern(kwargs, exhaustive=True) |
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_destructure.names(structure) # Raise ValueError if there are duplicates |
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return functools.partial(_decorate, self.matchers, structure) |
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mwchase /
python-structured-data
