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| # SPDX-License-Identifier: MIT | |
| import functools | |
| import types | |
| from ._make import _make_ne | |
| _operation_names = {"eq": "==", "lt": "<", "le": "<=", "gt": ">", "ge": ">="} | |
| def cmp_using( | |
| eq=None, | |
| lt=None, | |
| le=None, | |
| gt=None, | |
| ge=None, | |
| require_same_type=True, | |
| class_name="Comparable", | |
| ): | |
| """ | |
| Create a class that can be passed into `attrs.field`'s ``eq``, ``order``, | |
| and ``cmp`` arguments to customize field comparison. | |
| The resulting class will have a full set of ordering methods if at least | |
| one of ``{lt, le, gt, ge}`` and ``eq`` are provided. | |
| :param Optional[callable] eq: `callable` used to evaluate equality of two | |
| objects. | |
| :param Optional[callable] lt: `callable` used to evaluate whether one | |
| object is less than another object. | |
| :param Optional[callable] le: `callable` used to evaluate whether one | |
| object is less than or equal to another object. | |
| :param Optional[callable] gt: `callable` used to evaluate whether one | |
| object is greater than another object. | |
| :param Optional[callable] ge: `callable` used to evaluate whether one | |
| object is greater than or equal to another object. | |
| :param bool require_same_type: When `True`, equality and ordering methods | |
| will return `NotImplemented` if objects are not of the same type. | |
| :param Optional[str] class_name: Name of class. Defaults to 'Comparable'. | |
| See `comparison` for more details. | |
| .. versionadded:: 21.1.0 | |
| """ | |
| body = { | |
| "__slots__": ["value"], | |
| "__init__": _make_init(), | |
| "_requirements": [], | |
| "_is_comparable_to": _is_comparable_to, | |
| } | |
| # Add operations. | |
| num_order_functions = 0 | |
| has_eq_function = False | |
| if eq is not None: | |
| has_eq_function = True | |
| body["__eq__"] = _make_operator("eq", eq) | |
| body["__ne__"] = _make_ne() | |
| if lt is not None: | |
| num_order_functions += 1 | |
| body["__lt__"] = _make_operator("lt", lt) | |
| if le is not None: | |
| num_order_functions += 1 | |
| body["__le__"] = _make_operator("le", le) | |
| if gt is not None: | |
| num_order_functions += 1 | |
| body["__gt__"] = _make_operator("gt", gt) | |
| if ge is not None: | |
| num_order_functions += 1 | |
| body["__ge__"] = _make_operator("ge", ge) | |
| type_ = types.new_class( | |
| class_name, (object,), {}, lambda ns: ns.update(body) | |
| ) | |
| # Add same type requirement. | |
| if require_same_type: | |
| type_._requirements.append(_check_same_type) | |
| # Add total ordering if at least one operation was defined. | |
| if 0 < num_order_functions < 4: | |
| if not has_eq_function: | |
| # functools.total_ordering requires __eq__ to be defined, | |
| # so raise early error here to keep a nice stack. | |
| msg = "eq must be define is order to complete ordering from lt, le, gt, ge." | |
| raise ValueError(msg) | |
| type_ = functools.total_ordering(type_) | |
| return type_ | |
| def _make_init(): | |
| """ | |
| Create __init__ method. | |
| """ | |
| def __init__(self, value): | |
| """ | |
| Initialize object with *value*. | |
| """ | |
| self.value = value | |
| return __init__ | |
| def _make_operator(name, func): | |
| """ | |
| Create operator method. | |
| """ | |
| def method(self, other): | |
| if not self._is_comparable_to(other): | |
| return NotImplemented | |
| result = func(self.value, other.value) | |
| if result is NotImplemented: | |
| return NotImplemented | |
| return result | |
| method.__name__ = f"__{name}__" | |
| method.__doc__ = ( | |
| f"Return a {_operation_names[name]} b. Computed by attrs." | |
| ) | |
| return method | |
| def _is_comparable_to(self, other): | |
| """ | |
| Check whether `other` is comparable to `self`. | |
| """ | |
| return all(func(self, other) for func in self._requirements) | |
| def _check_same_type(self, other): | |
| """ | |
| Return True if *self* and *other* are of the same type, False otherwise. | |
| """ | |
| return other.value.__class__ is self.value.__class__ | |