structured_data.adt._add_prewritten_methods() - Code Metrics - Inspection of "Try hacking at the complexity measures" - mwchase/python-structured-data - Measure and Improve Code Quality continuously with Scrutinizer

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Push — master ( 4e65d0...795f8c )

by Max

created 2019-08-26 12:42 UTC

structured_data.adt._add_prewritten_methods() B

↳ Parent: structured_data.adt

Complexity

Conditions

Size

Total Lines	26
Code Lines	19

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	5
eloc	19
nop	5
dl	0
loc	26
rs	8.9833
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 ._adt_constructor import ADTConstructor
from ._adt_constructor import make_constructor
from ._ctor import get_args
from ._prewritten_methods import SUBCLASS_ORDER
from ._prewritten_methods import PrewrittenProductMethods
from ._prewritten_methods import PrewrittenSumMethods

_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


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


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.
    """
    for function in functions:
        name = _name(cls, function)
        if getattr(object, name, None) is not getattr(cls, name, None):
            return name
    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 _add_methods(cls: typing.Type[_T], do_set, *methods):
    methods_were_set = False
    if do_set:
        methods_were_set = not _set_new_functions(cls, *methods)
    return methods_were_set


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, 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":
            value = None
        _nillable_write(args, key, value)
    return args


def _tuple_getter(index: int):
    # TODO: __name__ and __qualname__
    @property
    def getter(self):
        return tuple.__getitem__(self, index)

    return getter


def _add_prewritten_methods(_cls: typing.Type[_T], _repr, eq, order, src):
    _set_new_functions(_cls, src.__setattr__, src.__delattr__)
    _set_new_functions(_cls, src.__bool__)

    _add_methods(_cls, _repr, src.__repr__)

    equality_methods_were_set = _add_methods(_cls, eq, src.__eq__, src.__ne__)

    if equality_methods_were_set:
        _cls.__hash__ = src.__hash__

    if not order:
        return

    if not equality_methods_were_set:
        raise ValueError(
            "Can't add ordering methods if equality methods are provided."
        )
    collision = _set_new_functions(
        _cls, src.__lt__, src.__le__, src.__gt__, src.__ge__
    )
    if collision:
        raise TypeError(
            "Cannot overwrite attribute {collision} in class "
            "{name}. Consider using functools.total_ordering".format(
                collision=collision, name=_cls.__name__
            )
        )


def _process_class(_cls: typing.Type[_T], _repr, eq, order) -> typing.Type[_T]:
    if order and not eq:
        raise ValueError("eq must be true if order is true")

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

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

    SUBCLASS_ORDER[_cls] = tuple(subclass_order)

    _cls.__init_subclass__ = PrewrittenSumMethods.__init_subclass__  # type: ignore

    _sum_new(_cls, frozenset(subclass_order))

    _add_prewritten_methods(_cls, _repr, eq, order, PrewrittenSumMethods)

    return _cls


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 __init_subclass__(cls, *, repr=True, eq=True, order=False, **kwargs):
        super().__init_subclass__(**kwargs)
        if not issubclass(cls, ADTConstructor):
            _process_class(cls, repr, eq, order)


class Product(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):
        cls, *args = args
        values = cls.__defaults.copy()
        fields_iter = iter(cls.__annotations)
        for arg, field in zip(args, fields_iter):
            values[field] = arg
        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)
        return super(Product, cls).__new__(
            cls, [values[field] for field in cls.__annotations]
        )

    def __init_subclass__(cls, *, repr=True, eq=True, order=False, **kwargs):
        super().__init_subclass__(**kwargs)
        if "__annotations__" not in vars(cls):
            return
        if order and not eq:
            raise ValueError("eq must be true if order is true")

        cls.__annotations = _product_args_from_annotations(cls)

        cls.__defaults = {}
        field_names = iter(reversed(tuple(cls.__annotations)))
        for field in field_names:
            default = getattr(cls, field, inspect.Parameter.empty)
            if default is inspect.Parameter.empty:
                break
            cls.__defaults[field] = default
        for field in field_names:
            if (
                getattr(cls, field, inspect.Parameter.empty)
                is not inspect.Parameter.empty
            ):
                raise TypeError

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

        for index, field in enumerate(cls.__annotations):
            setattr(cls, field, _tuple_getter(index))

        _add_prewritten_methods(cls, repr, eq, order, PrewrittenProductMethods)


__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 ._adt_constructor import ADTConstructor
49			from ._adt_constructor import make_constructor
50			from ._ctor import get_args
51			from ._prewritten_methods import SUBCLASS_ORDER
52			from ._prewritten_methods import PrewrittenProductMethods
53			from ._prewritten_methods import PrewrittenSumMethods
54
55			_T = typing.TypeVar("_T")
56
57
58			if typing.TYPE_CHECKING: # pragma: nocover
59
60			class Ctor:
61			"""Dummy class for type-checking purposes."""
62
63			class ConcreteCtor(typing.Generic[_T]):
64			"""Wrapper class for type-checking purposes.
65
66			The type parameter should be a Tuple type of fixed size.
67			Classes containing this annotation (meaning they haven't been
68			processed by the ``adt`` decorator) should not be instantiated.
69			"""
70
71
72			else:
73			from ._ctor import Ctor
74
75
76			def _name(cls: typing.Type[_T], function) -> str:
77			"""Return the name of a function accessed through a descriptor."""
78			return function.__get__(None, cls).__name__
79
80
81			def _set_new_functions(cls: typing.Type[_T], *functions) -> typing.Optional[str]:
82			"""Attempt to set the attributes corresponding to the functions on cls.
83
84			If any attributes are already defined, fail before setting any, and
85			return the already-defined name.
86			"""
87			for function in functions:
88			name = _name(cls, function)
89			if getattr(object, name, None) is not getattr(cls, name, None):
90			return name
91			for function in functions:
92			setattr(cls, _name(cls, function), function)
93			return None
94
95
96			_K = typing.TypeVar("_K")
97			_V = typing.TypeVar("_V")
98
99
100			def _nillable_write(dct: typing.Dict[_K, _V], key: _K, value: typing.Optional[_V]):
101			if value is None:
102			dct.pop(key, typing.cast(_V, None))
103			else:
104			dct[key] = value
105
106
107			def _add_methods(cls: typing.Type[_T], do_set, *methods):
108			methods_were_set = False
109			if do_set:
110			methods_were_set = not _set_new_functions(cls, *methods)
111			return methods_were_set
112
113
114			def _sum_new(_cls: typing.Type[_T], subclasses):
115			def base(cls, args):
116			return super(_cls, cls).__new__(cls, args)
117
118			new = _cls.__dict__.get("__new__", staticmethod(base))
119
120			def __new__(cls, args):
121			if cls not in subclasses:
122			raise TypeError
123			return new.__get__(None, cls)(cls, args)
124
125			_cls.__new__ = staticmethod(__new__) # type: ignore
126
127
128			def _product_new(
129			_cls: typing.Type[_T],
130			annotations: typing.Dict[str, typing.Any],
131			defaults: typing.Dict[str, typing.Any],
132			):
133			def __new__(args, *kwargs):
134			cls, *args = args
135			return super(_cls, cls).__new__(cls, args, *kwargs)
136
137			__new__.__signature__ = inspect.signature(__new__).replace(
138			parameters=[inspect.Parameter("cls", inspect.Parameter.POSITIONAL_ONLY)]
139			+ [
140			inspect.Parameter(
141			field,
142			inspect.Parameter.POSITIONAL_OR_KEYWORD,
143			annotation=annotation,
144			default=defaults.get(field, inspect.Parameter.empty),
145			)
146			for (field, annotation) in annotations.items()
147			]
148			)
149			_cls.__new__ = __new__
150
151
152			def _all_annotations(
153			cls: typing.Type[_T]
154			) -> typing.Iterator[typing.Tuple[typing.Type[_T], str, typing.Any]]:
155			for superclass in reversed(cls.__mro__):
156			for key, value in vars(superclass).get("__annotations__", {}).items():
157			yield (superclass, key, value)
158
159
160			def _sum_args_from_annotations(cls: typing.Type[_T]) -> typing.Dict[str, typing.Tuple]:
161			args: typing.Dict[str, typing.Tuple] = {}
162			for superclass, key, value in _all_annotations(cls):
163			_nillable_write(
164			args, key, get_args(value, vars(sys.modules[superclass.__module__]))
165			)
166			return args
167
168
169			def _product_args_from_annotations(
170			cls: typing.Type[_T]
171			) -> typing.Dict[str, typing.Any]:
172			args: typing.Dict[str, typing.Any] = {}
173			for superclass, key, value in _all_annotations(cls):
174			if value == "None":
175			value = None
176			_nillable_write(args, key, value)
177			return args
178
179
180			def _tuple_getter(index: int):
181			# TODO: __name__ and __qualname__
182			@property
183			def getter(self):
184			return tuple.__getitem__(self, index)
185
186			return getter
187
188
189			def _add_prewritten_methods(_cls: typing.Type[_T], _repr, eq, order, src):
190			_set_new_functions(_cls, src.__setattr__, src.__delattr__)
191			_set_new_functions(_cls, src.__bool__)
192
193			_add_methods(_cls, _repr, src.__repr__)
194
195			equality_methods_were_set = _add_methods(_cls, eq, src.__eq__, src.__ne__)
196
197			if equality_methods_were_set:
198			_cls.__hash__ = src.__hash__
199
200			if not order:
201			return
202
203			if not equality_methods_were_set:
204			raise ValueError(
205			"Can't add ordering methods if equality methods are provided."
206			)
207			collision = _set_new_functions(
208			_cls, src.__lt__, src.__le__, src.__gt__, src.__ge__
209			)
210			if collision:
211			raise TypeError(
212			"Cannot overwrite attribute {collision} in class "
213			"{name}. Consider using functools.total_ordering".format(
214			collision=collision, name=_cls.__name__
215			)
216			)
217
218
219			def _process_class(_cls: typing.Type[_T], _repr, eq, order) -> typing.Type[_T]:
220			if order and not eq:
221			raise ValueError("eq must be true if order is true")
222
223			subclass_order: typing.List[typing.Type[_T]] = []
224
225			for name, args in _sum_args_from_annotations(_cls).items():
226			make_constructor(_cls, name, args, subclass_order)
227
228			SUBCLASS_ORDER[_cls] = tuple(subclass_order)
229
230			_cls.__init_subclass__ = PrewrittenSumMethods.__init_subclass__ # type: ignore
231
232			_sum_new(_cls, frozenset(subclass_order))
233
234			_add_prewritten_methods(_cls, _repr, eq, order, PrewrittenSumMethods)
235
236			return _cls
237
238
239			class Sum:
240			"""Base class of classes with disjoint constructors.
241
242			Examines PEP 526 __annotations__ to determine subclasses.
243
244			If repr is true, a __repr__() method is added to the class.
245			If order is true, rich comparison dunder methods are added.
246
247			The Sum class examines the class to find Ctor annotations.
248			A Ctor annotation is the adt.Ctor class itself, or the result of indexing
249			the class, either with a single type hint, or a tuple of type hints.
250			All other annotations are ignored.
251
252			The subclass is not subclassable, but has subclasses at each of the
253			names that had Ctor annotations. Each subclass takes a fixed number of
254			arguments, corresponding to the type hints given to its annotation, if any.
255			"""
256
257			__slots__ = ()
258
259			def __init_subclass__(cls, , repr=True, eq=True, order=False, *kwargs):
260			super().__init_subclass__(**kwargs)
261			if not issubclass(cls, ADTConstructor):
262			_process_class(cls, repr, eq, order)
263
264
265			class Product(ADTConstructor, tuple):
266			"""Base class of classes with typed fields.
267
268			Examines PEP 526 __annotations__ to determine fields.
269
270			If repr is true, a __repr__() method is added to the class.
271			If order is true, rich comparison dunder methods are added.
272
273			The Product class examines the class to find annotations.
274			Annotations with a value of "None" are discarded.
275			Fields may have default values, and can be set to inspect.empty to
276			indicate "no default".
277
278			The subclass is subclassable. The implementation was designed with a focus
279			on flexibility over ideals of purity, and therefore provides various
280			optional facilities that conflict with, for example, Liskov
281			substitutability. For the purposes of matching, each class is considered
282			distinct.
283			"""
284
285			__slots__ = ()
286
287			def __new__(args, *kwargs):
288			cls, *args = args
289			values = cls.__defaults.copy()
290			fields_iter = iter(cls.__annotations)
291			for arg, field in zip(args, fields_iter):
292			values[field] = arg
293			for field in fields_iter:
294			if field in values and field not in kwargs:
295			continue
296			values[field] = kwargs.pop(field)
297			if kwargs:
298			raise TypeError(kwargs)
299			return super(Product, cls).__new__(
300			cls, [values[field] for field in cls.__annotations]
301			)
302
303			def __init_subclass__(cls, , repr=True, eq=True, order=False, *kwargs):
304			super().__init_subclass__(**kwargs)
305			if "__annotations__" not in vars(cls):
306			return
307			if order and not eq:
308			raise ValueError("eq must be true if order is true")
309
310			cls.__annotations = _product_args_from_annotations(cls)
311
312			cls.__defaults = {}
313			field_names = iter(reversed(tuple(cls.__annotations)))
314			for field in field_names:
315			default = getattr(cls, field, inspect.Parameter.empty)
316			if default is inspect.Parameter.empty:
317			break
318			cls.__defaults[field] = default
319			for field in field_names:
320			if (
321			getattr(cls, field, inspect.Parameter.empty)
322			is not inspect.Parameter.empty
323			):
324			raise TypeError
325
326			_product_new(cls, cls.__annotations, cls.__defaults)
327
328			for index, field in enumerate(cls.__annotations):
329			setattr(cls, field, _tuple_getter(index))
330
331			_add_prewritten_methods(cls, repr, eq, order, PrewrittenProductMethods)
332
333
334			__all__ = ["Ctor", "Product", "Sum"]
335

mwchase / python-structured-data

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