structured_data.adt.Product.__init_subclass__() - Code Metrics - Inspection of "Only have the logic once" - mwchase/python-structured-data - Measure and Improve Code Quality continuously with Scrutinizer

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Push — master ( 982e46...1ba64f )

by Max

created 2019-09-02 16:51 UTC

structured_data.adt.Product.__init_subclass__() B

↳ Parent: structured_data.adt

Complexity

Conditions

Size

Total Lines	40
Code Lines	30

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	6
eloc	30
nop	6
dl	0
loc	40
rs	8.2266
c	0
b	0
f	0

"""Base classes for defining abstract data types.

This module provides three public members, which are used together.

Given a structure, possibly a choice of different structures, that you'd like
to associate with a type:

- First, create a class, that subclasses the Sum class.
- Then, for each possible structure, add an attribute annotation to the class
  with the desired name of the constructor, and a type of ``Ctor``, with the
  types within the constructor as arguments.

To look inside an ADT instance, use the functions from the
:mod:`structured_data.match` module.

Putting it together:

>>> from structured_data import match
>>> class Example(Sum):
...     FirstConstructor: Ctor[int, str]
...     SecondConstructor: Ctor[bytes]
...     ThirdConstructor: Ctor
...     def __iter__(self):
...         matchable = match.Matchable(self)
...         if matchable(Example.FirstConstructor(match.pat.count, match.pat.string)):
...             count, string = matchable[match.pat.count, match.pat.string]
...             for _ in range(count):
...                 yield string
...         elif matchable(Example.SecondConstructor(match.pat.bytes)):
...             bytes_ = matchable[match.pat.bytes]
...             for byte in bytes_:
...                 yield chr(byte)
...         elif matchable(Example.ThirdConstructor()):
...             yield "Third"
...             yield "Constructor"
>>> list(Example.FirstConstructor(5, "abc"))
['abc', 'abc', 'abc', 'abc', 'abc']
>>> list(Example.SecondConstructor(b"abc"))
['a', 'b', 'c']
>>> list(Example.ThirdConstructor())
['Third', 'Constructor']
"""

import inspect
import sys
import typing

from . import _adt_constructor
from . import _ctor
from . import _prewritten_methods

_T = typing.TypeVar("_T")


if typing.TYPE_CHECKING:  # pragma: nocover

    class Ctor:
        """Dummy class for type-checking purposes."""

    class ConcreteCtor(typing.Generic[_T]):
        """Wrapper class for type-checking purposes.

        The type parameter should be a Tuple type of fixed size.
        Classes containing this annotation (meaning they haven't been
        processed by the ``adt`` decorator) should not be instantiated.
        """


else:
    from ._ctor import Ctor


# This is fine.
def _name(cls: typing.Type[_T], function) -> str:
    """Return the name of a function accessed through a descriptor."""
    return function.__get__(None, cls).__name__


# This is mostly fine, though the list of classes is somewhat ad-hoc, to say
# the least.
def _cant_set_new_functions(cls: typing.Type[_T], *functions) -> typing.Optional[str]:
    for function in functions:
        name = _name(cls, function)
        existing = getattr(cls, name, None)
        if existing not in (
            getattr(object, name, None),
            getattr(Product, name, None),
            None,
            function,
        ):
            return name
    return None


def _set_new_functions(cls: typing.Type[_T], *functions) -> typing.Optional[str]:
    """Attempt to set the attributes corresponding to the functions on cls.

    If any attributes are already defined, fail *before* setting any, and
    return the already-defined name.
    """
    cant_set = _cant_set_new_functions(cls, *functions)
    if cant_set:
        return cant_set
    for function in functions:
        setattr(cls, _name(cls, function), function)
    return None


_K = typing.TypeVar("_K")
_V = typing.TypeVar("_V")


def _nillable_write(dct: typing.Dict[_K, _V], key: _K, value: typing.Optional[_V]):
    if value is None:
        dct.pop(key, typing.cast(_V, None))
    else:
        dct[key] = value


def _sum_new(_cls: typing.Type[_T], subclasses):
    def base(cls, args):
        return super(_cls, cls).__new__(cls, args)

    new = _cls.__dict__.get("__new__", staticmethod(base))

    def __new__(cls, args):
        if cls not in subclasses:
            raise TypeError
        return new.__get__(None, cls)(cls, args)

    _cls.__new__ = staticmethod(__new__)  # type: ignore


def _product_new(
    _cls: typing.Type[_T],
    annotations: typing.Dict[str, typing.Any],
    defaults: typing.Dict[str, typing.Any],
):
    def __new__(*args, **kwargs):
        cls, *args = args
        return super(_cls, cls).__new__(cls, *args, **kwargs)

    __new__.__signature__ = inspect.signature(__new__).replace(
        parameters=[inspect.Parameter("cls", inspect.Parameter.POSITIONAL_ONLY)]
        + [
            inspect.Parameter(
                field,
                inspect.Parameter.POSITIONAL_OR_KEYWORD,
                annotation=annotation,
                default=defaults.get(field, inspect.Parameter.empty),
            )
            for (field, annotation) in annotations.items()
        ]
    )
    _cls.__new__ = __new__


def _all_annotations(
    cls: typing.Type[_T]
) -> typing.Iterator[typing.Tuple[typing.Type[_T], str, typing.Any]]:
    for superclass in reversed(cls.__mro__):
        for key, value in vars(superclass).get("__annotations__", {}).items():
            yield (superclass, key, value)


def _sum_args_from_annotations(cls: typing.Type[_T]) -> typing.Dict[str, typing.Tuple]:
    args: typing.Dict[str, typing.Tuple] = {}
    for superclass, key, value in _all_annotations(cls):
        _nillable_write(
            args, key, _ctor.get_args(value, vars(sys.modules[superclass.__module__]))
        )
    return args


def _product_args_from_annotations(
    cls: typing.Type[_T]
) -> typing.Dict[str, typing.Any]:
    args: typing.Dict[str, typing.Any] = {}
    for superclass, key, value in _all_annotations(cls):
        if value == "None" or _ctor.annotation_is_classvar(
            value, vars(sys.modules[superclass.__module__])
        ):
            value = None
        _nillable_write(args, key, value)
    return args


def _ordering_options_are_valid(*, eq, order):
    if order and not eq:
        raise ValueError("eq must be true if order is true")


def _set_ordering(*, can_set, setter, cls, source):
    if not can_set:
        raise ValueError("Can't add ordering methods if equality methods are provided.")
    collision = setter(cls, source.__lt__, source.__le__, source.__gt__, source.__ge__)
    if collision:
        raise TypeError(
            "Cannot overwrite attribute {collision} in class "
            "{name}. Consider using functools.total_ordering".format(
                collision=collision, name=cls.__name__
            )
        )


def _values_non_empty(cls, field_names):
    for field in field_names:
        default = getattr(cls, field, inspect.Parameter.empty)
        if default is inspect.Parameter.empty:
            return
        yield (field, default)


def _values_until_non_empty(cls, field_names):
    for field in field_names:
        default = getattr(cls, field, inspect.Parameter.empty)
        if default is not inspect.Parameter.empty:
            yield


def _extract_defaults(*, cls, annotations):
    field_names = iter(reversed(tuple(annotations)))
    defaults = dict(_values_non_empty(cls, field_names))
    for _ in _values_until_non_empty(cls, field_names):
        raise TypeError
    return defaults


def _unpack_args(*, args, kwargs, fields, values):
    fields_iter = iter(fields)
    values.update({field: arg for (arg, field) in zip(args, fields_iter)})
    for field in fields_iter:
        if field in values and field not in kwargs:
            continue
        values[field] = kwargs.pop(field)
    if kwargs:
        raise TypeError(kwargs)


class Sum:
    """Base class of classes with disjoint constructors.

    Examines PEP 526 __annotations__ to determine subclasses.

    If repr is true, a __repr__() method is added to the class.
    If order is true, rich comparison dunder methods are added.

    The Sum class examines the class to find Ctor annotations.
    A Ctor annotation is the adt.Ctor class itself, or the result of indexing
    the class, either with a single type hint, or a tuple of type hints.
    All other annotations are ignored.

    The subclass is not subclassable, but has subclasses at each of the
    names that had Ctor annotations. Each subclass takes a fixed number of
    arguments, corresponding to the type hints given to its annotation, if any.
    """

    __slots__ = ()

    def __new__(*args, **kwargs):  # pylint: disable=no-method-argument
        cls, *args = args
        if not issubclass(cls, _adt_constructor.ADTConstructor):
            raise TypeError
        return super(Sum, cls).__new__(cls, *args, **kwargs)

    # Both of these are for consistency with modules defined in the stdlib.
    # BOOM!
    def __init_subclass__(
        cls,
        *,
        repr=True,  # pylint: disable=redefined-builtin
        eq=True,  # pylint: disable=invalid-name
        order=False,
        **kwargs
    ):
        super().__init_subclass__(**kwargs)
        if issubclass(cls, _adt_constructor.ADTConstructor):
            return
        _ordering_options_are_valid(eq=eq, order=order)

        subclass_order: typing.List[typing.Type[_T]] = []

        for name, args in _sum_args_from_annotations(cls).items():
            _adt_constructor.make_constructor(cls, name, args, subclass_order)

        _prewritten_methods.SUBCLASS_ORDER[cls] = tuple(subclass_order)

        source = _prewritten_methods.PrewrittenSumMethods

        cls.__init_subclass__ = source.__init_subclass__  # type: ignore

        _sum_new(cls, frozenset(subclass_order))

        _set_new_functions(cls, source.__setattr__, source.__delattr__)
        _set_new_functions(cls, source.__bool__)

        if repr:
            _set_new_functions(cls, source.__repr__)

        equality_methods_were_set = False
        if eq:
            equality_methods_were_set = not _set_new_functions(
                cls, source.__eq__, source.__ne__
            )

        if equality_methods_were_set:
            cls.__hash__ = source.__hash__

        if order:
            _set_ordering(
                can_set=equality_methods_were_set,
                setter=_set_new_functions,
                cls=cls,
                source=source,
            )


class _ProductMethod:
    name = None
    field_check = None

    def __getattr__(self, name):
        self.field_check = name
        return self

    def __set_name__(self, owner, name):
        del owner
        self.name = name

    def __get__(self, instance, owner):
        if getattr(owner, self.field_check):
            return getattr(
                _prewritten_methods.PrewrittenProductMethods, self.name
            ).__get__(instance, owner)
        target = owner if instance is None else instance
        return getattr(super(Product, target), self.name)

    def __set__(self, instance, value):
        # Don't care about this coverage
        raise AttributeError  # pragma: nocover

    def __delete__(self, instance):
        # Don't care about this coverage
        raise AttributeError  # pragma: nocover


class Product(_adt_constructor.ADTConstructor, tuple):
    """Base class of classes with typed fields.

    Examines PEP 526 __annotations__ to determine fields.

    If repr is true, a __repr__() method is added to the class.
    If order is true, rich comparison dunder methods are added.

    The Product class examines the class to find annotations.
    Annotations with a value of "None" are discarded.
    Fields may have default values, and can be set to inspect.empty to
    indicate "no default".

    The subclass is subclassable. The implementation was designed with a focus
    on flexibility over ideals of purity, and therefore provides various
    optional facilities that conflict with, for example, Liskov
    substitutability. For the purposes of matching, each class is considered
    distinct.
    """

    __slots__ = ()

    def __new__(*args, **kwargs):  # pylint: disable=no-method-argument
        cls, *args = args
        if cls is Product:
            raise TypeError
        # Probably a result of not having positional-only args.
        values = cls.__defaults.copy()  # pylint: disable=protected-access
        _unpack_args(
            args=args,
            kwargs=kwargs,
            fields=cls.__fields,  # pylint: disable=protected-access
            values=values,
        )
        return super(Product, cls).__new__(
            cls,
            [
                values[field]
                for field in cls.__fields  # pylint: disable=protected-access
            ],
        )

    __repr = True
    __eq = True
    __order = False
    __eq_succeeded = None

    # Both of these are for consistency with modules defined in the stdlib.
    # BOOM!
    def __init_subclass__(
        cls,
        *,
        repr=None,  # pylint: disable=redefined-builtin
        eq=None,  # pylint: disable=invalid-name
        order=None,
        **kwargs
    ):
        super().__init_subclass__(**kwargs)

        if repr is not None:
            cls.__repr = repr
        if eq is not None:
            cls.__eq = eq
        if order is not None:
            cls.__order = order

        _ordering_options_are_valid(eq=cls.__eq, order=cls.__order)

        cls.__annotations = _product_args_from_annotations(cls)
        cls.__fields = {field: index for (index, field) in enumerate(cls.__annotations)}

        cls.__defaults = _extract_defaults(cls=cls, annotations=cls.__annotations)

        _product_new(cls, cls.__annotations, cls.__defaults)

        source = _prewritten_methods.PrewrittenProductMethods

        cls.__eq_succeeded = False
        if cls.__eq:
            cls.__eq_succeeded = not _cant_set_new_functions(
                cls, source.__eq__, source.__ne__
            )

        if cls.__order:
            _set_ordering(
                can_set=cls.__eq_succeeded,
                setter=_cant_set_new_functions,
                cls=cls,
                source=source,
            )

    def __dir__(self):
        return super().__dir__() + list(self.__fields)

    def __getattribute__(self, name):
        try:
            return super().__getattribute__(name)
        except AttributeError:
            index = self.__fields.get(name)
            if index is None:
                raise
            return tuple.__getitem__(self, index)

    __setattr__ = _prewritten_methods.PrewrittenProductMethods.__setattr__
    __delattr__ = _prewritten_methods.PrewrittenProductMethods.__delattr__
    __bool__ = _prewritten_methods.PrewrittenProductMethods.__bool__

    __repr__ = _ProductMethod().__repr
    __hash__ = _ProductMethod().__eq_succeeded
    __eq__ = _ProductMethod().__eq_succeeded
    __ne__ = _ProductMethod().__eq_succeeded
    __lt__ = _ProductMethod().__order
    __le__ = _ProductMethod().__order
    __gt__ = _ProductMethod().__order
    __ge__ = _ProductMethod().__order


__all__ = ["Ctor", "Product", "Sum"]


1			"""Base classes for defining abstract data types.
2
3			This module provides three public members, which are used together.
4
5			Given a structure, possibly a choice of different structures, that you'd like
6			to associate with a type:
7
8			- First, create a class, that subclasses the Sum class.
9			- Then, for each possible structure, add an attribute annotation to the class
10			with the desired name of the constructor, and a type of ``Ctor``, with the
11			types within the constructor as arguments.
12
13			To look inside an ADT instance, use the functions from the
14			:mod:`structured_data.match` module.
15
16			Putting it together:
17
18			>>> from structured_data import match
19			>>> class Example(Sum):
20			... FirstConstructor: Ctor[int, str]
21			... SecondConstructor: Ctor[bytes]
22			... ThirdConstructor: Ctor
23			... def __iter__(self):
24			... matchable = match.Matchable(self)
25			... if matchable(Example.FirstConstructor(match.pat.count, match.pat.string)):
26			... count, string = matchable[match.pat.count, match.pat.string]
27			... for _ in range(count):
28			... yield string
29			... elif matchable(Example.SecondConstructor(match.pat.bytes)):
30			... bytes_ = matchable[match.pat.bytes]
31			... for byte in bytes_:
32			... yield chr(byte)
33			... elif matchable(Example.ThirdConstructor()):
34			... yield "Third"
35			... yield "Constructor"
36			>>> list(Example.FirstConstructor(5, "abc"))
37			['abc', 'abc', 'abc', 'abc', 'abc']
38			>>> list(Example.SecondConstructor(b"abc"))
39			['a', 'b', 'c']
40			>>> list(Example.ThirdConstructor())
41			['Third', 'Constructor']
42			"""
43
44			import inspect
45			import sys
46			import typing
47
48			from . import _adt_constructor
49			from . import _ctor
50			from . import _prewritten_methods
51
52			_T = typing.TypeVar("_T")
53
54
55			if typing.TYPE_CHECKING: # pragma: nocover
56
57			class Ctor:
58			"""Dummy class for type-checking purposes."""
59
60			class ConcreteCtor(typing.Generic[_T]):
61			"""Wrapper class for type-checking purposes.
62
63			The type parameter should be a Tuple type of fixed size.
64			Classes containing this annotation (meaning they haven't been
65			processed by the ``adt`` decorator) should not be instantiated.
66			"""
67
68
69			else:
70			from ._ctor import Ctor
71
72
73			# This is fine.
74			def _name(cls: typing.Type[_T], function) -> str:
75			"""Return the name of a function accessed through a descriptor."""
76			return function.__get__(None, cls).__name__
77
78
79			# This is mostly fine, though the list of classes is somewhat ad-hoc, to say
80			# the least.
81			def _cant_set_new_functions(cls: typing.Type[_T], *functions) -> typing.Optional[str]:
82			for function in functions:
83			name = _name(cls, function)
84			existing = getattr(cls, name, None)
85			if existing not in (
86			getattr(object, name, None),
87			getattr(Product, name, None),
88			None,
89			function,
90			):
91			return name
92			return None
93
94
95			def _set_new_functions(cls: typing.Type[_T], *functions) -> typing.Optional[str]:
96			"""Attempt to set the attributes corresponding to the functions on cls.
97
98			If any attributes are already defined, fail before setting any, and
99			return the already-defined name.
100			"""
101			cant_set = _cant_set_new_functions(cls, *functions)
102			if cant_set:
103			return cant_set
104			for function in functions:
105			setattr(cls, _name(cls, function), function)
106			return None
107
108
109			_K = typing.TypeVar("_K")
110			_V = typing.TypeVar("_V")
111
112
113			def _nillable_write(dct: typing.Dict[_K, _V], key: _K, value: typing.Optional[_V]):
114			if value is None:
115			dct.pop(key, typing.cast(_V, None))
116			else:
117			dct[key] = value
118
119
120			def _sum_new(_cls: typing.Type[_T], subclasses):
121			def base(cls, args):
122			return super(_cls, cls).__new__(cls, args)
123
124			new = _cls.__dict__.get("__new__", staticmethod(base))
125
126			def __new__(cls, args):
127			if cls not in subclasses:
128			raise TypeError
129			return new.__get__(None, cls)(cls, args)
130
131			_cls.__new__ = staticmethod(__new__) # type: ignore
132
133
134			def _product_new(
135			_cls: typing.Type[_T],
136			annotations: typing.Dict[str, typing.Any],
137			defaults: typing.Dict[str, typing.Any],
138			):
139			def __new__(args, *kwargs):
140			cls, *args = args
141			return super(_cls, cls).__new__(cls, args, *kwargs)
142
143			__new__.__signature__ = inspect.signature(__new__).replace(
144			parameters=[inspect.Parameter("cls", inspect.Parameter.POSITIONAL_ONLY)]
145			+ [
146			inspect.Parameter(
147			field,
148			inspect.Parameter.POSITIONAL_OR_KEYWORD,
149			annotation=annotation,
150			default=defaults.get(field, inspect.Parameter.empty),
151			)
152			for (field, annotation) in annotations.items()
153			]
154			)
155			_cls.__new__ = __new__
156
157
158			def _all_annotations(
159			cls: typing.Type[_T]
160			) -> typing.Iterator[typing.Tuple[typing.Type[_T], str, typing.Any]]:
161			for superclass in reversed(cls.__mro__):
162			for key, value in vars(superclass).get("__annotations__", {}).items():
163			yield (superclass, key, value)
164
165
166			def _sum_args_from_annotations(cls: typing.Type[_T]) -> typing.Dict[str, typing.Tuple]:
167			args: typing.Dict[str, typing.Tuple] = {}
168			for superclass, key, value in _all_annotations(cls):
169			_nillable_write(
170			args, key, _ctor.get_args(value, vars(sys.modules[superclass.__module__]))
171			)
172			return args
173
174
175			def _product_args_from_annotations(
176			cls: typing.Type[_T]
177			) -> typing.Dict[str, typing.Any]:
178			args: typing.Dict[str, typing.Any] = {}
179			for superclass, key, value in _all_annotations(cls):
180			if value == "None" or _ctor.annotation_is_classvar(
181			value, vars(sys.modules[superclass.__module__])
182			):
183			value = None
184			_nillable_write(args, key, value)
185			return args
186
187
188			def _ordering_options_are_valid(*, eq, order):
189			if order and not eq:
190			raise ValueError("eq must be true if order is true")
191
192
193			def _set_ordering(*, can_set, setter, cls, source):
194			if not can_set:
195			raise ValueError("Can't add ordering methods if equality methods are provided.")
196			collision = setter(cls, source.__lt__, source.__le__, source.__gt__, source.__ge__)
197			if collision:
198			raise TypeError(
199			"Cannot overwrite attribute {collision} in class "
200			"{name}. Consider using functools.total_ordering".format(
201			collision=collision, name=cls.__name__
202			)
203			)
204
205
206			def _values_non_empty(cls, field_names):
207			for field in field_names:
208			default = getattr(cls, field, inspect.Parameter.empty)
209			if default is inspect.Parameter.empty:
210			return
211			yield (field, default)
212
213
214			def _values_until_non_empty(cls, field_names):
215			for field in field_names:
216			default = getattr(cls, field, inspect.Parameter.empty)
217			if default is not inspect.Parameter.empty:
218			yield
219
220
221			def _extract_defaults(*, cls, annotations):
222			field_names = iter(reversed(tuple(annotations)))
223			defaults = dict(_values_non_empty(cls, field_names))
224			for _ in _values_until_non_empty(cls, field_names):
225			raise TypeError
226			return defaults
227
228
229			def _unpack_args(*, args, kwargs, fields, values):
230			fields_iter = iter(fields)
231			values.update({field: arg for (arg, field) in zip(args, fields_iter)})
232			for field in fields_iter:
233			if field in values and field not in kwargs:
234			continue
235			values[field] = kwargs.pop(field)
236			if kwargs:
237			raise TypeError(kwargs)
238
239
240			class Sum:
241			"""Base class of classes with disjoint constructors.
242
243			Examines PEP 526 __annotations__ to determine subclasses.
244
245			If repr is true, a __repr__() method is added to the class.
246			If order is true, rich comparison dunder methods are added.
247
248			The Sum class examines the class to find Ctor annotations.
249			A Ctor annotation is the adt.Ctor class itself, or the result of indexing
250			the class, either with a single type hint, or a tuple of type hints.
251			All other annotations are ignored.
252
253			The subclass is not subclassable, but has subclasses at each of the
254			names that had Ctor annotations. Each subclass takes a fixed number of
255			arguments, corresponding to the type hints given to its annotation, if any.
256			"""
257
258			__slots__ = ()
259
260			def __new__(args, *kwargs): # pylint: disable=no-method-argument
261			cls, *args = args
262			if not issubclass(cls, _adt_constructor.ADTConstructor):
263			raise TypeError
264			return super(Sum, cls).__new__(cls, args, *kwargs)
265
266			# Both of these are for consistency with modules defined in the stdlib.
267			# BOOM!
268			def __init_subclass__(
269			cls,
270			*,
271			repr=True, # pylint: disable=redefined-builtin
272			eq=True, # pylint: disable=invalid-name
273			order=False,
274			**kwargs
275			):
276			super().__init_subclass__(**kwargs)
277			if issubclass(cls, _adt_constructor.ADTConstructor):
278			return
279			_ordering_options_are_valid(eq=eq, order=order)
280
281			subclass_order: typing.List[typing.Type[_T]] = []
282
283			for name, args in _sum_args_from_annotations(cls).items():
284			_adt_constructor.make_constructor(cls, name, args, subclass_order)
285
286			_prewritten_methods.SUBCLASS_ORDER[cls] = tuple(subclass_order)
287
288			source = _prewritten_methods.PrewrittenSumMethods
289
290			cls.__init_subclass__ = source.__init_subclass__ # type: ignore
291
292			_sum_new(cls, frozenset(subclass_order))
293
294			_set_new_functions(cls, source.__setattr__, source.__delattr__)
295			_set_new_functions(cls, source.__bool__)
296
297			if repr:
298			_set_new_functions(cls, source.__repr__)
299
300			equality_methods_were_set = False
301			if eq:
302			equality_methods_were_set = not _set_new_functions(
303			cls, source.__eq__, source.__ne__
304			)
305
306			if equality_methods_were_set:
307			cls.__hash__ = source.__hash__
308
309			if order:
310			_set_ordering(
311			can_set=equality_methods_were_set,
312			setter=_set_new_functions,
313			cls=cls,
314			source=source,
315			)
316
317
318			class _ProductMethod:
319			name = None
320			field_check = None
321
322			def __getattr__(self, name):
323			self.field_check = name
324			return self
325
326			def __set_name__(self, owner, name):
327			del owner
328			self.name = name
329
330			def __get__(self, instance, owner):
331			if getattr(owner, self.field_check):
332			return getattr(
333			_prewritten_methods.PrewrittenProductMethods, self.name
334			).__get__(instance, owner)
335			target = owner if instance is None else instance
336			return getattr(super(Product, target), self.name)
337
338			def __set__(self, instance, value):
339			# Don't care about this coverage
340			raise AttributeError # pragma: nocover
341
342			def __delete__(self, instance):
343			# Don't care about this coverage
344			raise AttributeError # pragma: nocover
345
346
347			class Product(_adt_constructor.ADTConstructor, tuple):
348			"""Base class of classes with typed fields.
349
350			Examines PEP 526 __annotations__ to determine fields.
351
352			If repr is true, a __repr__() method is added to the class.
353			If order is true, rich comparison dunder methods are added.
354
355			The Product class examines the class to find annotations.
356			Annotations with a value of "None" are discarded.
357			Fields may have default values, and can be set to inspect.empty to
358			indicate "no default".
359
360			The subclass is subclassable. The implementation was designed with a focus
361			on flexibility over ideals of purity, and therefore provides various
362			optional facilities that conflict with, for example, Liskov
363			substitutability. For the purposes of matching, each class is considered
364			distinct.
365			"""
366
367			__slots__ = ()
368
369			def __new__(args, *kwargs): # pylint: disable=no-method-argument
370			cls, *args = args
371			if cls is Product:
372			raise TypeError
373			# Probably a result of not having positional-only args.
374			values = cls.__defaults.copy() # pylint: disable=protected-access
375			_unpack_args(
376			args=args,
377			kwargs=kwargs,
378			fields=cls.__fields, # pylint: disable=protected-access
379			values=values,
380			)
381			return super(Product, cls).__new__(
382			cls,
383			[
384			values[field]
385			for field in cls.__fields # pylint: disable=protected-access
386			],
387			)
388
389			__repr = True
390			__eq = True
391			__order = False
392			__eq_succeeded = None
393
394			# Both of these are for consistency with modules defined in the stdlib.
395			# BOOM!
396			def __init_subclass__(
397			cls,
398			*,
399			repr=None, # pylint: disable=redefined-builtin
400			eq=None, # pylint: disable=invalid-name
401			order=None,
402			**kwargs
403			):
404			super().__init_subclass__(**kwargs)
405
406			if repr is not None:
407			cls.__repr = repr
408			if eq is not None:
409			cls.__eq = eq
410			if order is not None:
411			cls.__order = order
412
413			_ordering_options_are_valid(eq=cls.__eq, order=cls.__order)
414
415			cls.__annotations = _product_args_from_annotations(cls)
416			cls.__fields = {field: index for (index, field) in enumerate(cls.__annotations)}
417
418			cls.__defaults = _extract_defaults(cls=cls, annotations=cls.__annotations)
419
420			_product_new(cls, cls.__annotations, cls.__defaults)
421
422			source = _prewritten_methods.PrewrittenProductMethods
423
424			cls.__eq_succeeded = False
425			if cls.__eq:
426			cls.__eq_succeeded = not _cant_set_new_functions(
427			cls, source.__eq__, source.__ne__
428			)
429
430			if cls.__order:
431			_set_ordering(
432			can_set=cls.__eq_succeeded,
433			setter=_cant_set_new_functions,
434			cls=cls,
435			source=source,
436			)
437
438			def __dir__(self):
439			return super().__dir__() + list(self.__fields)
440
441			def __getattribute__(self, name):
442			try:
443			return super().__getattribute__(name)
444			except AttributeError:
445			index = self.__fields.get(name)
446			if index is None:
447			raise
448			return tuple.__getitem__(self, index)
449
450			__setattr__ = _prewritten_methods.PrewrittenProductMethods.__setattr__
451			__delattr__ = _prewritten_methods.PrewrittenProductMethods.__delattr__
452			__bool__ = _prewritten_methods.PrewrittenProductMethods.__bool__
453
454			__repr__ = _ProductMethod().__repr
455			__hash__ = _ProductMethod().__eq_succeeded
456			__eq__ = _ProductMethod().__eq_succeeded
457			__ne__ = _ProductMethod().__eq_succeeded
458			__lt__ = _ProductMethod().__order
459			__le__ = _ProductMethod().__order
460			__gt__ = _ProductMethod().__order
461			__ge__ = _ProductMethod().__order
462
463
464			__all__ = ["Ctor", "Product", "Sum"]
465

mwchase / python-structured-data

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structured_data.adt.Product.__init_subclass__() B

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