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"""Class decorator for defining abstract data types.""" |
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import sys |
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import typing |
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from ._ctor import Ctor |
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from ._ctor import get_args |
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from ._enum_constructor import make_constructor |
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from ._prewritten_methods import SUBCLASS_ORDER |
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from ._prewritten_methods import PrewrittenMethods |
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def _name(cls, function) -> str: |
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"""Return the name of a function accessed through a descriptor.""" |
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return function.__get__(None, cls).__name__ |
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def _set_new_functions(cls, *functions) -> typing.Optional[str]: |
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"""Attempt to set the attributes corresponding to the functions on cls. |
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If any attributes are already defined, fail *before* setting any, and |
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return the already-defined name. |
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""" |
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for function in functions: |
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if _name(cls, function) in cls.__dict__: |
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return _name(cls, function) |
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for function in functions: |
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setattr(cls, _name(cls, function), function) |
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return None |
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def _enum_super(_cls): |
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def base(cls, args): |
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return super(_cls, cls).__new__(cls, args) |
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return base |
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def _make_nested_new(_cls, subclasses, base__new__): |
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@staticmethod |
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def __new__(cls, args): |
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if cls not in subclasses: |
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raise TypeError |
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return base__new__(cls, args) |
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return __new__ |
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def _nillable_write(dct, key, value): |
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if value is None: |
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dct.pop(key, None) |
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else: |
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dct[key] = value |
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def _add_methods(cls, do_set, *methods): |
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methods_were_set = False |
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if do_set: |
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methods_were_set = not _set_new_functions(cls, *methods) |
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return methods_were_set |
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def _set_hash(cls, set_hash): |
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if set_hash: |
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cls.__hash__ = PrewrittenMethods.__hash__ |
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def _add_order(cls, set_order, equality_methods_were_set): |
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if set_order: |
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if not equality_methods_were_set: |
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raise ValueError( |
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"Can't add ordering methods if equality methods are provided.") |
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collision = _set_new_functions( |
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cls, |
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PrewrittenMethods.__lt__, |
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PrewrittenMethods.__le__, |
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PrewrittenMethods.__gt__, |
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PrewrittenMethods.__ge__ |
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) |
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if collision: |
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raise TypeError( |
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'Cannot overwrite attribute {collision} in class ' |
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'{name}. Consider using functools.total_ordering'.format( |
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collision=collision, name=cls.__name__)) |
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def _custom_new(cls, subclasses): |
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basic_new = _make_nested_new(cls, subclasses, _enum_super(cls)) |
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if _set_new_functions(cls, basic_new): |
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augmented_new = _make_nested_new(cls, subclasses, cls.__new__) |
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cls.__new__ = augmented_new |
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def _args_from_annotations(cls): |
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args = {} |
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for superclass in reversed(cls.__mro__): |
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for key, value in getattr(superclass, '__annotations__', {}).items(): |
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_nillable_write( |
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args, key, get_args(value, vars(sys.modules[superclass.__module__]))) |
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return args |
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def _process_class(_cls, _repr, eq, order): |
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if order and not eq: |
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raise ValueError('eq must be true if order is true') |
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subclasses = set() |
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subclass_order = [] |
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108
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for name, args in _args_from_annotations(_cls).items(): |
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make_constructor(_cls, name, args, subclasses, subclass_order) |
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111
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SUBCLASS_ORDER[_cls] = tuple(subclass_order) |
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_cls.__init_subclass__ = PrewrittenMethods.__init_subclass__ |
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_custom_new(_cls, subclasses) |
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_set_new_functions( |
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_cls, PrewrittenMethods.__setattr__, PrewrittenMethods.__delattr__) |
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_set_new_functions(_cls, PrewrittenMethods.__bool__) |
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_add_methods(_cls, _repr, PrewrittenMethods.__repr__) |
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equality_methods_were_set = _add_methods( |
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_cls, eq, PrewrittenMethods.__eq__, PrewrittenMethods.__ne__) |
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_set_hash(_cls, equality_methods_were_set) |
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128
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_add_order(_cls, order, equality_methods_were_set) |
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return _cls |
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132
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133
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def enum(_cls=None, *, repr=True, eq=True, order=False): |
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"""Decorate a class to be an algebraic data type.""" |
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135
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136
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def wrap(cls): |
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"""Return the processed class.""" |
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return _process_class(cls, repr, eq, order) |
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if _cls is None: |
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return wrap |
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143
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return wrap(_cls) |
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145
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146
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__all__ = ['Ctor', 'enum'] |
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147
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mwchase /
python-structured-data
