structured_data.enum._args() - Code Metrics - Inspection of "Move line up" - mwchase/python-structured-data - Measure and Improve Code Quality continuously with Scrutinizer

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by Max

created 2018-07-19 18:14 UTC

structured_data.enum._args() A

↳ Parent: structured_data.enum

Complexity

Conditions

Size

Total Lines	7
Code Lines	7

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	3
eloc	7
nop	2
dl	0
loc	7
rs	10
c	0
b	0
f	0

"""Class decorator for defining abstract data types."""

import ast
import sys
import typing
import weakref

import astor

from ._enum_constructor import make_constructor
from ._prewritten_methods import SUBCLASS_ORDER
from ._prewritten_methods import PrewrittenMethods

_CTOR_CACHE = {}


ARGS = weakref.WeakKeyDictionary()


class Ctor:
    """Marker class for enum constructors.

    To use, index with a sequence of types, and annotate a variable in an
    enum-decorated class with it.
    """

    def __new__(cls, args):
        if args == ():
            return cls
        self = object.__new__(cls)
        ARGS[self] = args
        return _CTOR_CACHE.setdefault(args, self)

    def __init_subclass__(cls, **kwargs):
        raise TypeError

    def __class_getitem__(cls, args):
        if not isinstance(args, tuple):
            args = (args,)
        return cls(args)


ARGS[Ctor] = ()


def _interpret_args_from_non_string(constructor):
    try:
        return ARGS.get(constructor)
    except TypeError:
        return None


def _parse_constructor(constructor):
    try:
        return ast.parse(constructor, mode='eval')
    except Exception:
        raise ValueError('parsing annotation failed')


def _get_args_from_index(index):
    if isinstance(index, ast.Tuple):
        return tuple(astor.to_source(elt) for elt in index.elts)
    return (astor.to_source(index),)


def _checked_eval(source, global_ns):
    try:
        return eval(source, global_ns)
    except Exception:
        return None


def _extract_tuple_ast(constructor, global_ns):
    ctor_ast = _parse_constructor(constructor)
    if (
            isinstance(ctor_ast.body, ast.Subscript)
            and isinstance(ctor_ast.body.slice, ast.Index)):
        index = ctor_ast.body.slice.value
        ctor_ast.body = ctor_ast.body.value
        value = _checked_eval(compile(ctor_ast, '<annotation>', 'eval'), global_ns)
        if value is Ctor:
            return _get_args_from_index(index)
        if value is None:
            return None
    return _interpret_args_from_non_string(_checked_eval(constructor, global_ns))


def _args(constructor, global_ns):
    if isinstance(constructor, str):
        try:
            return _extract_tuple_ast(constructor, global_ns)
        except ValueError:
            return None
    return _interpret_args_from_non_string(constructor)


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


def _set_new_functions(cls, *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:
        if _name(cls, function) in cls.__dict__:
            return _name(cls, function)
    for function in functions:
        setattr(cls, _name(cls, function), function)
    return None


def _enum_super(_cls):
    def base(cls, args):
        return super(_cls, cls).__new__(cls, args)
    return base


def _make_nested_new(_cls, subclasses, base__new__):
    @staticmethod
    def __new__(cls, args):
        if cls not in subclasses:
            raise TypeError
        return base__new__(cls, args)
    return __new__


def _nillable_write(dct, key, value):
    if value is None:
        dct.pop(key, None)
    else:
        dct[key] = value


def _process_class(_cls, _repr, eq, order):
    if order and not eq:
        raise ValueError('eq must be true if order is true')

    args = {}
    subclasses = set()
    subclass_order = []
    for cls in reversed(_cls.__mro__):
        for key, value in getattr(cls, '__annotations__', {}).items():
            _nillable_write(
                args, key, _args(value, vars(sys.modules[cls.__module__])))

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

    SUBCLASS_ORDER[_cls] = tuple(subclass_order)

    _cls.__init_subclass__ = PrewrittenMethods.__init_subclass__

    if _set_new_functions(_cls, _make_nested_new(_cls, subclasses, _enum_super(_cls))):
        _cls.__new__ = _make_nested_new(_cls, subclasses, _cls.__new__)

    _set_new_functions(
        _cls, PrewrittenMethods.__setattr__, PrewrittenMethods.__delattr__)
    _set_new_functions(_cls, PrewrittenMethods.__bool__)

    if _repr:
        _set_new_functions(_cls, PrewrittenMethods.__repr__)

    equality_methods_were_set = False

    if eq:
        equality_methods_were_set = not _set_new_functions(
            _cls, PrewrittenMethods.__eq__, PrewrittenMethods.__ne__)

    if equality_methods_were_set:
        _cls.__hash__ = PrewrittenMethods.__hash__

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

    return _cls


def enum(_cls=None, *, repr=True, eq=True, order=False):
    """Decorate a class to be an algebraic data type."""

    def wrap(cls):
        """Return the processed class."""
        return _process_class(cls, repr, eq, order)

    if _cls is None:
        return wrap

    return wrap(_cls)


__all__ = ['Ctor', 'enum']


1			"""Class decorator for defining abstract data types."""
2
3			import ast
4			import sys
5			import typing
6			import weakref
7
8			import astor
9
10			from ._enum_constructor import make_constructor
11			from ._prewritten_methods import SUBCLASS_ORDER
12			from ._prewritten_methods import PrewrittenMethods
13
14			_CTOR_CACHE = {}
15
16
17			ARGS = weakref.WeakKeyDictionary()
18
19
20			class Ctor:
21			"""Marker class for enum constructors.
22
23			To use, index with a sequence of types, and annotate a variable in an
24			enum-decorated class with it.
25			"""
26
27			def __new__(cls, args):
28			if args == ():
29			return cls
30			self = object.__new__(cls)
31			ARGS[self] = args
32			return _CTOR_CACHE.setdefault(args, self)
33
34			def __init_subclass__(cls, **kwargs):
35			raise TypeError
36
37			def __class_getitem__(cls, args):
38			if not isinstance(args, tuple):
39			args = (args,)
40			return cls(args)
41
42
43			ARGS[Ctor] = ()
44
45
46			def _interpret_args_from_non_string(constructor):
47			try:
48			return ARGS.get(constructor)
49			except TypeError:
50			return None
51
52
53			def _parse_constructor(constructor):
54			try:
55			return ast.parse(constructor, mode='eval')
56			except Exception:
57			raise ValueError('parsing annotation failed')
58
59
60			def _get_args_from_index(index):
61			if isinstance(index, ast.Tuple):
62			return tuple(astor.to_source(elt) for elt in index.elts)
63			return (astor.to_source(index),)
64
65
66			def _checked_eval(source, global_ns):
67			try:
68			return eval(source, global_ns)
69			except Exception:
70			return None
71
72
73			def _extract_tuple_ast(constructor, global_ns):
74			ctor_ast = _parse_constructor(constructor)
75			if (
76			isinstance(ctor_ast.body, ast.Subscript)
77			and isinstance(ctor_ast.body.slice, ast.Index)):
78			index = ctor_ast.body.slice.value
79			ctor_ast.body = ctor_ast.body.value
80			value = _checked_eval(compile(ctor_ast, '<annotation>', 'eval'), global_ns)
81			if value is Ctor:
82			return _get_args_from_index(index)
83			if value is None:
84			return None
85			return _interpret_args_from_non_string(_checked_eval(constructor, global_ns))
86
87
88			def _args(constructor, global_ns):
89			if isinstance(constructor, str):
90			try:
91			return _extract_tuple_ast(constructor, global_ns)
92			except ValueError:
93			return None
94			return _interpret_args_from_non_string(constructor)
95
96
97			def _name(cls, function) -> str:
98			"""Return the name of a function accessed through a descriptor."""
99			return function.__get__(None, cls).__name__
100
101
102			def _set_new_functions(cls, *functions) -> typing.Optional[str]:
103			"""Attempt to set the attributes corresponding to the functions on cls.
104
105			If any attributes are already defined, fail before setting any, and
106			return the already-defined name.
107			"""
108			for function in functions:
109			if _name(cls, function) in cls.__dict__:
110			return _name(cls, function)
111			for function in functions:
112			setattr(cls, _name(cls, function), function)
113			return None
114
115
116			def _enum_super(_cls):
117			def base(cls, args):
118			return super(_cls, cls).__new__(cls, args)
119			return base
120
121
122			def _make_nested_new(_cls, subclasses, base__new__):
123			@staticmethod
124			def __new__(cls, args):
125			if cls not in subclasses:
126			raise TypeError
127			return base__new__(cls, args)
128			return __new__
129
130
131			def _nillable_write(dct, key, value):
132			if value is None:
133			dct.pop(key, None)
134			else:
135			dct[key] = value
136
137
138			def _process_class(_cls, _repr, eq, order):
139			if order and not eq:
140			raise ValueError('eq must be true if order is true')
141
142			args = {}
143			subclasses = set()
144			subclass_order = []
145			for cls in reversed(_cls.__mro__):
146			for key, value in getattr(cls, '__annotations__', {}).items():
147			_nillable_write(
148			args, key, _args(value, vars(sys.modules[cls.__module__])))
149
150			for name, args_ in args.items():
151			make_constructor(_cls, name, args_, subclasses, subclass_order)
152
153			SUBCLASS_ORDER[_cls] = tuple(subclass_order)
154
155			_cls.__init_subclass__ = PrewrittenMethods.__init_subclass__
156
157			if _set_new_functions(_cls, _make_nested_new(_cls, subclasses, _enum_super(_cls))):
158			_cls.__new__ = _make_nested_new(_cls, subclasses, _cls.__new__)
159
160			_set_new_functions(
161			_cls, PrewrittenMethods.__setattr__, PrewrittenMethods.__delattr__)
162			_set_new_functions(_cls, PrewrittenMethods.__bool__)
163
164			if _repr:
165			_set_new_functions(_cls, PrewrittenMethods.__repr__)
166
167			equality_methods_were_set = False
168
169			if eq:
170			equality_methods_were_set = not _set_new_functions(
171			_cls, PrewrittenMethods.__eq__, PrewrittenMethods.__ne__)
172
173			if equality_methods_were_set:
174			_cls.__hash__ = PrewrittenMethods.__hash__
175
176			if order:
177			if not equality_methods_were_set:
178			raise ValueError(
179			"Can't add ordering methods if equality methods are provided.")
180			collision = _set_new_functions(
181			_cls,
182			PrewrittenMethods.__lt__,
183			PrewrittenMethods.__le__,
184			PrewrittenMethods.__gt__,
185			PrewrittenMethods.__ge__
186			)
187			if collision:
188			raise TypeError(
189			'Cannot overwrite attribute {collision} in class '
190			'{name}. Consider using functools.total_ordering'.format(
191			collision=collision, name=_cls.__name__))
192
193			return _cls
194
195
196			def enum(_cls=None, *, repr=True, eq=True, order=False):
197			"""Decorate a class to be an algebraic data type."""
198
199			def wrap(cls):
200			"""Return the processed class."""
201			return _process_class(cls, repr, eq, order)
202
203			if _cls is None:
204			return wrap
205
206			return wrap(_cls)
207
208
209			__all__ = ['Ctor', 'enum']
210

mwchase / python-structured-data

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