Namespace.__setitem__() - Code Metrics - Inspection of "It... passed..." - mwchase/class-namespaces - Measure and Improve Code Quality continuously with Scrutinizer

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Push — master ( 0243d6...2a9af7 )

by Max

created 2016-11-26 17:07 UTC

Namespace.setitem() B

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Complexity

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Size

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Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	9
CRAP Score	6.0359

Importance

Changes	4
Bugs	0	Features	0

Metric	Value
cc	6
c	4
b	0
f	0
dl	0
loc	12
ccs	9
cts	10
cp	0.9
crap	6.0359
rs	8

"""Class Namespaces (internal module).

All of the guts of the class namespace implementation.

"""


# See https://blog.ionelmc.ro/2015/02/09/understanding-python-metaclasses/

import collections.abc
import functools
import itertools
import weakref

from . import ops
from .descriptor_inspector import _DescriptorInspector
from .flags import ENABLE_SET_NAME
from .proxy import _Proxy
from .scope_proxy import _ScopeProxy


_PROXY_INFOS = weakref.WeakKeyDictionary()


def _mro_to_chained(mro, path):
    """Return a chained map of lookups for the given namespace and mro."""
    return collections.ChainMap(*[
        Namespace.get_namespace(cls, path) for cls in
        itertools.takewhile(
            functools.partial(Namespace.no_blocker, path),
            (cls for cls in mro if isinstance(cls, _Namespaceable))) if
        Namespace.namespace_exists(path, cls)])


def _instance_map(ns_proxy):
    """Return a map, possibly chained, of lookups for the given instance."""
    dct, instance, _ = _PROXY_INFOS[ns_proxy]
    if instance is not None:
        if isinstance(instance, _Namespaceable):
            return _mro_to_chained(instance.__mro__, dct.path)
        else:
            return Namespace.get_namespace(instance, dct.path)
    else:
        return {}


def _mro_map(ns_proxy):
    """Return a chained map of lookups for the given owner class."""
    dct, _, owner = _PROXY_INFOS[ns_proxy]
    mro = owner.__mro__
    parent_object = dct.parent_object
    index = mro.index(parent_object)
    mro = mro[index:]
    return _mro_to_chained(mro, dct.path)


def _retarget(ns_proxy):
    """Convert a class lookup to an instance lookup, if needed."""
    dct, instance, owner = _PROXY_INFOS[ns_proxy]
    if instance is None and isinstance(type(owner), _Namespaceable):
        instance, owner = owner, type(owner)
        dct = Namespace.get_namespace(owner, dct.path)
        ns_proxy = _NamespaceProxy(dct, instance, owner)
    return ns_proxy


class _NamespaceProxy(_Proxy):

    """Proxy object for manipulating and querying namespaces."""

    __slots__ = '__weakref__',

    def __init__(self, dct, instance, owner):
        _PROXY_INFOS[self] = dct, instance, owner

    def __dir__(self):
        return collections.ChainMap(_instance_map(self), _mro_map(self))

    def __getattribute__(self, name):
        self = _retarget(self)
        _, instance, owner = _PROXY_INFOS[self]
        instance_map = _instance_map(self)
        mro_map = _mro_map(self)
        instance_value = ops.get(instance_map, name)
        mro_value = ops.get(mro_map, name)
        if ops.is_data(mro_value):
            return mro_value.get(instance, owner)
        elif issubclass(owner, type) and ops.has_get(instance_value):
            return instance_value.get(None, instance)
        elif instance_value is not None:
            return instance_value.object
        elif ops.has_get(mro_value):
            return mro_value.get(instance, owner)
        elif mro_value is not None:
            return mro_value.object
        else:
            raise AttributeError(name)

    def __setattr__(self, name, value):
        self = _retarget(self)
        dct, instance, owner = _PROXY_INFOS[self]
        if instance is None:
            real_map = Namespace.get_namespace(owner, dct.path)
            real_map[name] = value
            return
        mro_map = _mro_map(self)
        target_value = ops.get_data(mro_map, name)
        if target_value is not None:
            # These lines will be called on a data descriptor.
            target_value.set(instance, value)
            return
        instance_map = Namespace.get_namespace(instance, dct.path)
        instance_map[name] = value

    def __delattr__(self, name):
        self = _retarget(self)
        dct, instance, owner = _PROXY_INFOS[self]
        real_map = Namespace.get_namespace(owner, dct.path)
        if instance is None:
            ops.delete(real_map, name)
            return
        value = ops.get_data(real_map, name)
        if value is not None:
            # These lines will be called on a data descriptor.
            value.delete(instance)
            return
        instance_map = Namespace.get_namespace(instance, dct.path)
        ops.delete(instance_map, name)


class Namespace(dict):

    """Namespace."""

    __slots__ = (
        'name', 'scope', 'parent', 'active', 'parent_object', 'needs_setup')

    __namespaces = {}

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        bad_values = tuple(
            value for value in self.values() if
            isinstance(value, (Namespace, _Proxy)))
        if bad_values:
            raise ValueError('Bad values: {}'.format(bad_values))
        self.name = None
        self.scope = None
        self.parent = None
        self.active = False
        self.parent_object = None
        self.needs_setup = False

    @classmethod
    def premake(cls, name, parent):
        """Return an empty namespace with the given name and parent."""
        self = cls()
        self.name = name
        self.parent = parent
        return self

    # Hold up. Do we need a symmetric addon to __delitem__?
    # I forget how this works.
    def __setitem__(self, key, value):
        if (
                self.scope is not None and
                isinstance(value, self.scope.scope_proxy)):
            value = self.scope.proxies[value]
        if isinstance(value, (_ScopeProxy, _NamespaceProxy)):
            raise ValueError('Cannot move scopes between classes.')
        if isinstance(value, Namespace):
            value.push(key, self.scope, self)
            if self.parent_object is not None:
                value.add(self.parent_object)
        super().__setitem__(key, value)

    def __enter__(self):
        self.needs_setup = True
        self.activate()
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        if self.name is None:
            raise RuntimeError('Namespace must be named.')
        self.deactivate()

    @property
    def path(self):
        """Return the full path of the namespace."""
        if self.name is None or self.parent is None:
            # This line can be hit by Namespace().path.
            raise ValueError
        if isinstance(self.parent, Namespace):
            parent_path = self.parent.path
        else:
            parent_path = ()
        return parent_path + (self.name,)

    @classmethod
    def __get_helper(cls, target, path):
        """Return the namespace for `target` at `path`, create if needed."""
        if isinstance(target, _Namespaceable):
            path_ = target, path
            namespaces = cls.__namespaces
        else:
            path_ = path
            try:
                namespaces = target.__namespaces
            except AttributeError:
                namespaces = {}
                target.__namespaces = namespaces
        return path_, namespaces

    @classmethod
    def namespace_exists(cls, path, target):
        """Return whether the given namespace exists."""
        path_, namespaces = cls.__get_helper(target, path)
        return path_ in namespaces

    @classmethod
    def get_namespace(cls, target, path):
        """Return a namespace with given target and path, create if needed."""
        path_, namespaces = cls.__get_helper(target, path)
        try:
            return namespaces[path_]
        except KeyError:
            if len(path) == 1:
                parent = {}
            else:
                parent = cls.get_namespace(target, path[:-1])
            return namespaces.setdefault(path_, cls.premake(path[-1], parent))

    @classmethod
    def no_blocker(cls, path, cls_):
        """Return False if there's a non-Namespace object in the path."""
        try:
            namespace = vars(cls_)
            for name in path:
                namespace = namespace[name]
                if not isinstance(namespace, cls):
                    return False
        except KeyError:
try:
    raises_exception()
except:  # Could be removed
    pass
            pass
        return True

    def add(self, target):
        """Add self as a namespace under target."""
        path, namespaces = self.__get_helper(target, self.path)
        res = namespaces.setdefault(path, self)
        if res is self:
            self.parent_object = target

    def set_if_none(self, name, value):
        """Set the attribute `name` to `value`, if it's initially None."""
        if getattr(self, name) is None:
            setattr(self, name, value)

    def validate_assignment(self, name, scope):
class SomeClass:
    def some_method(self):
        """Do x and return foo."""
        if name != self.name:
            raise ValueError('Cannot rename namespace')
        if scope is not self.scope:
            # It should be possible to hit this line by assigning a namespace
            # into another class. It may not be, however.
            raise ValueError('Cannot reuse namespace')

    def validate_parent(self, parent):
class SomeClass:
    def some_method(self):
        """Do x and return foo."""
        if parent is not self.parent:
            # This line can be hit by assigning a namespace into another
            # namespace.
            raise ValueError('Cannot reparent namespace')

    def push(self, name, scope, parent):
        """Bind self to the given name and scope, and activate."""
        self.set_if_none('name', name)
        self.set_if_none('scope', scope)
        self.set_if_none('parent', parent)
        self.validate_assignment(name, scope)
        self.validate_parent(parent)
        self.scope.namespaces.append(self)
        if self.needs_setup:
            self.activate()

    def activate(self):
        """Take over as the scope for the target."""
        if self.active:
            raise ValueError('Cannot double-activate.')
        if self.scope is not None:
            self.validate_parent(self.scope.dicts[0])
            self.active = True
            self.scope.dicts.insert(0, self)
            self.needs_setup = False

    def deactivate(self):
        """Stop being the scope for the target."""
        if self.scope is not None and self.active:
            self.active = False
            self.scope.dicts.pop(0)

    def __get__(self, instance, owner):
        return _NamespaceProxy(self, instance, owner)

    def __bool__(self):
class Foo:
    def some_method(self, x, y):
        return x + y;
        return True


class _NamespaceScope(collections.abc.MutableMapping):

    """The class creation namespace for _Namespaceables."""

    __slots__ = 'dicts', 'namespaces', 'proxies', 'scope_proxy'

    def __init__(self, dct):
        self.dicts = [dct]
        self.namespaces = []
        self.proxies = proxies = weakref.WeakKeyDictionary()

        class ScopeProxy(_ScopeProxy):

            """Local version of ScopeProxy for this scope."""

            __slots__ = ()

            def __init__(self, dct):
                super().__init__(dct, proxies)

        self.scope_proxy = ScopeProxy

    # Mapping methods need to know about the dot syntax.
    # Possibly namespaces themselves should know. Would simplify some things.

    def __getitem__(self, key):
        value = collections.ChainMap(*self.dicts)[key]
        if isinstance(value, Namespace):
            value = self.scope_proxy(value)
        return value

    def __setitem__(self, key, value):
        dct = self.dicts[0]
        # We just entered the context successfully.
        if value is dct:
            dct = self.dicts[1]
        if isinstance(value, Namespace):
            value.push(key, self, dct)
        if isinstance(value, self.scope_proxy):
            value = self.proxies[value]
            value.validate_parent(dct)
            value.validate_assignment(key, self)
        if isinstance(value, (_ScopeProxy, _NamespaceProxy)):
            raise ValueError('Cannot move scopes between classes.')
        dct[key] = value

    def __delitem__(self, key):
        del self.dicts[0][key]

    # These functions are incorrect and need to be rewritten.
    def __iter__(self):
        return iter(collections.ChainMap(*self.dicts))

    def __len__(self):
        return len(collections.ChainMap(*self.dicts))


_NAMESPACE_SCOPES = weakref.WeakKeyDictionary()


class _NamespaceBase:

    """Common base class for Namespaceable and its metaclass."""

    __slots__ = ()

    # Note: the dot format of invocation can "escape" self into other objects.
    # This is not intended behavior, and the result of using dots "too deeply"
    # should be considered undefined.
    # I would like it to be an error, if I can figure out how.

    @staticmethod
    def __is_proxy(value):
class SomeClass:
    def some_method(self):
        """Do x and return foo."""
        if not isinstance(value, _NamespaceProxy):
            # This line can be hit by doing what the error message says.
            raise ValueError('Given a dot attribute that went too deep.')
        return value

    def __getattribute__(self, name):
        parent, is_namespace, name_ = name.rpartition('.')
        if is_namespace:
            self_ = self
            for element in parent.split('.'):
                self_ = self.__is_proxy(getattr(self_, element))
            return getattr(getattr(self, parent), name_)
        return super(_NamespaceBase, type(self)).__getattribute__(self, name)

    def __setattr__(self, name, value):
        parent, is_namespace, name_ = name.rpartition('.')
        if is_namespace:
            setattr(self.__is_proxy(getattr(self, parent)), name_, value)
            return
        super(_NamespaceBase, type(self)).__setattr__(self, name, value)

    def __delattr__(self, name):
        parent, is_namespace, name_ = name.rpartition('.')
        if is_namespace:
            delattr(self.__is_proxy(getattr(self, parent)), name_)
            return
        # This line can be hit by deleting an attribute that isn't a namespace.
        super(_NamespaceBase, type(self)).__delattr__(self, name)


class _Namespaceable(_NamespaceBase, type):

    """Metaclass for classes that can contain namespaces.

    Using the metaclass directly is a bad idea. Use a base class instead.
    """

    @classmethod
    def __prepare__(mcs, name, bases, **kwargs):
        return _NamespaceScope(super().__prepare__(name, bases, **kwargs))

    def __new__(mcs, name, bases, dct, **kwargs):
        cls = super().__new__(mcs, name, bases, dct.dicts[0], **kwargs)
        if _DEFINED and not issubclass(cls, Namespaceable):
            # This line can be hit with class(metaclass=type(Namespaceable)):
            raise ValueError(
                'Cannot create a _Namespaceable that does not inherit from '
                'Namespaceable')
        _NAMESPACE_SCOPES[cls] = dct
        for namespace in dct.namespaces:
            namespace.add(cls)
            if ENABLE_SET_NAME:
                for name, value in namespace.items():
                    wrapped = _DescriptorInspector(value)
                    if wrapped.has_set_name:
                        wrapped.set_name(cls, name)
        return cls

    def __setattr__(cls, name, value):
        if (
                '.' not in name and isinstance(value, Namespace) and
                value.name != name):
            scope = _NAMESPACE_SCOPES[cls]
            value.push(name, scope, scope.dicts[-1])
            value.add(cls)
        super(_Namespaceable, type(cls)).__setattr__(cls, name, value)


_DEFINED = False


class Namespaceable(_NamespaceBase, metaclass=_Namespaceable):

    """Base class for classes that can contain namespaces.

    A note for people extending the functionality:
    The base class for Namespaceable and its metaclass uses a non-standard
    super() invocation in its definitions of several methods. This was the only
    way I could find to mitigate some bugs I encountered with a standard
    invocation. If you override any of methods defined on built-in types, I
    recommend this form for maximal reusability:

    super(class, type(self)).__method__(self, ...)

    This avoids confusing error messages in case self is a subclass of class,
    in addition to being an instance.

    If you're not delegating above Namespaceable, you can probably use the
    standard invocation, unless you bring about the above situation on your own
    types.
    """


_DEFINED = True


1		"""Class Namespaces (internal module).
2
3		All of the guts of the class namespace implementation.
4
5		"""
6
7
8		# See https://blog.ionelmc.ro/2015/02/09/understanding-python-metaclasses/
9
10	6	import collections.abc
11	6	import functools
12	6	import itertools
13	6	import weakref
14
15	6	from . import ops
16	6	from .descriptor_inspector import _DescriptorInspector
17	6	from .flags import ENABLE_SET_NAME
18	6	from .proxy import _Proxy
19	6	from .scope_proxy import _ScopeProxy
20
21
22	6	_PROXY_INFOS = weakref.WeakKeyDictionary()
23
24
25	6	def _mro_to_chained(mro, path):
26		"""Return a chained map of lookups for the given namespace and mro."""
27	6	return collections.ChainMap(*[
28		Namespace.get_namespace(cls, path) for cls in
29		itertools.takewhile(
30		functools.partial(Namespace.no_blocker, path),
31		(cls for cls in mro if isinstance(cls, _Namespaceable))) if
32		Namespace.namespace_exists(path, cls)])
33
34
35	6	def _instance_map(ns_proxy):
36		"""Return a map, possibly chained, of lookups for the given instance."""
37	6	dct, instance, _ = _PROXY_INFOS[ns_proxy]
38	6	if instance is not None:
39	6	if isinstance(instance, _Namespaceable):
40	6	return _mro_to_chained(instance.__mro__, dct.path)
41		else:
42	6	return Namespace.get_namespace(instance, dct.path)
43		else:
44	6	return {}
45
46
47	6	def _mro_map(ns_proxy):
48		"""Return a chained map of lookups for the given owner class."""
49	6	dct, _, owner = _PROXY_INFOS[ns_proxy]
50	6	mro = owner.__mro__
51	6	parent_object = dct.parent_object
52	6	index = mro.index(parent_object)
53	6	mro = mro[index:]
54	6	return _mro_to_chained(mro, dct.path)
55
56
57	6	def _retarget(ns_proxy):
58		"""Convert a class lookup to an instance lookup, if needed."""
59	6	dct, instance, owner = _PROXY_INFOS[ns_proxy]
60	6	if instance is None and isinstance(type(owner), _Namespaceable):
61	6	instance, owner = owner, type(owner)
62	6	dct = Namespace.get_namespace(owner, dct.path)
63	6	ns_proxy = _NamespaceProxy(dct, instance, owner)
64	6	return ns_proxy
65
66
67	6	class _NamespaceProxy(_Proxy):
68
69		"""Proxy object for manipulating and querying namespaces."""
70
71	6	__slots__ = '__weakref__',
72
73	6	def __init__(self, dct, instance, owner):
74	6	_PROXY_INFOS[self] = dct, instance, owner
75
76	6	def __dir__(self):
77	6	return collections.ChainMap(_instance_map(self), _mro_map(self))
78
79	6	def __getattribute__(self, name):
80	6	self = _retarget(self)
81	6	_, instance, owner = _PROXY_INFOS[self]
82	6	instance_map = _instance_map(self)
83	6	mro_map = _mro_map(self)
84	6	instance_value = ops.get(instance_map, name)
85	6	mro_value = ops.get(mro_map, name)
86	6	if ops.is_data(mro_value):
87	6	return mro_value.get(instance, owner)
88	6	elif issubclass(owner, type) and ops.has_get(instance_value):
89	6	return instance_value.get(None, instance)
90	6	elif instance_value is not None:
91	6	return instance_value.object
92	6	elif ops.has_get(mro_value):
93	6	return mro_value.get(instance, owner)
94	6	elif mro_value is not None:
95	6	return mro_value.object
96		else:
97	6	raise AttributeError(name)
98
99	6	def __setattr__(self, name, value):
100	6	self = _retarget(self)
101	6	dct, instance, owner = _PROXY_INFOS[self]
102	6	if instance is None:
103	6	real_map = Namespace.get_namespace(owner, dct.path)
104	6	real_map[name] = value
105	6	return
106	6	mro_map = _mro_map(self)
107	6	target_value = ops.get_data(mro_map, name)
108	6	if target_value is not None:
109		# These lines will be called on a data descriptor.
110	6	target_value.set(instance, value)
111	6	return
112	6	instance_map = Namespace.get_namespace(instance, dct.path)
113	6	instance_map[name] = value
114
115	6	def __delattr__(self, name):
116	6	self = _retarget(self)
117	6	dct, instance, owner = _PROXY_INFOS[self]
118	6	real_map = Namespace.get_namespace(owner, dct.path)
119	6	if instance is None:
120	6	ops.delete(real_map, name)
121	6	return
122	6	value = ops.get_data(real_map, name)
123	6	if value is not None:
124		# These lines will be called on a data descriptor.
125	6	value.delete(instance)
126	6	return
127	6	instance_map = Namespace.get_namespace(instance, dct.path)
128	6	ops.delete(instance_map, name)
129
130
131	6	class Namespace(dict):
132
133		"""Namespace."""
134
135	6	__slots__ = (
136		'name', 'scope', 'parent', 'active', 'parent_object', 'needs_setup')
137
138	6	__namespaces = {}
139
140	6	def __init__(self, args, *kwargs):
141	6	super().__init__(args, *kwargs)
142	6	bad_values = tuple(
143		value for value in self.values() if
144		isinstance(value, (Namespace, _Proxy)))
145	6	if bad_values:
146	6	raise ValueError('Bad values: {}'.format(bad_values))
147	6	self.name = None
148	6	self.scope = None
149	6	self.parent = None
150	6	self.active = False
151	6	self.parent_object = None
152	6	self.needs_setup = False
153
154	6	@classmethod
155		def premake(cls, name, parent):
156		"""Return an empty namespace with the given name and parent."""
157	6	self = cls()
158	6	self.name = name
159	6	self.parent = parent
160	6	return self
161
162		# Hold up. Do we need a symmetric addon to __delitem__?
163		# I forget how this works.
164	6	def __setitem__(self, key, value):
165	6	if (
166		self.scope is not None and
167		isinstance(value, self.scope.scope_proxy)):
168	6	value = self.scope.proxies[value]
169	6	if isinstance(value, (_ScopeProxy, _NamespaceProxy)):
170		raise ValueError('Cannot move scopes between classes.')
171	6	if isinstance(value, Namespace):
172	6	value.push(key, self.scope, self)
173	6	if self.parent_object is not None:
174	6	value.add(self.parent_object)
175	6	super().__setitem__(key, value)
176
177	6	def __enter__(self):
178	6	self.needs_setup = True
179	6	self.activate()
180	6	return self
181
182	6	def __exit__(self, exc_type, exc_value, traceback):
183	6	if self.name is None:
184	6	raise RuntimeError('Namespace must be named.')
185	6	self.deactivate()
186
187	6	@property
188		def path(self):
189		"""Return the full path of the namespace."""
190	6	if self.name is None or self.parent is None:
191		# This line can be hit by Namespace().path.
192	6	raise ValueError
193	6	if isinstance(self.parent, Namespace):
194	6	parent_path = self.parent.path
195		else:
196	6	parent_path = ()
197	6	return parent_path + (self.name,)
198
199	6	@classmethod
200		def __get_helper(cls, target, path):
201		"""Return the namespace for `target` at `path`, create if needed."""
202	6	if isinstance(target, _Namespaceable):
203	6	path_ = target, path
204	6	namespaces = cls.__namespaces
205		else:
206	6	path_ = path
207	6	try:
208	6	namespaces = target.__namespaces
209	6	except AttributeError:
210	6	namespaces = {}
211	6	target.__namespaces = namespaces
212	6	return path_, namespaces
213
214	6	@classmethod
215		def namespace_exists(cls, path, target):
216		"""Return whether the given namespace exists."""
217	6	path_, namespaces = cls.__get_helper(target, path)
218	6	return path_ in namespaces
219
220	6	@classmethod
221		def get_namespace(cls, target, path):
222		"""Return a namespace with given target and path, create if needed."""
223	6	path_, namespaces = cls.__get_helper(target, path)
224	6	try:
225	6	return namespaces[path_]
226	6	except KeyError:
227	6	if len(path) == 1:
228	6	parent = {}
229		else:
230	6	parent = cls.get_namespace(target, path[:-1])
231	6	return namespaces.setdefault(path_, cls.premake(path[-1], parent))
232
233	6	@classmethod
234		def no_blocker(cls, path, cls_):
235		"""Return False if there's a non-Namespace object in the path."""
236	6	try:
237	6	namespace = vars(cls_)
238	6	for name in path:
239	6	namespace = namespace[name]
240	6	if not isinstance(namespace, cls):
241	6	return False
242	6	except KeyError:
		1 ignored issue – show Unused Code introduced 2016-11-20 03:53 UTC by Report Bug Copy Issue Report This except handler seems to be unused and could be removed. Except handlers which only contain `pass` and do not have an `else` clause can usually simply be removed: try: raises_exception() except: # Could be removed pass Loading history...
243	6	pass
244	6	return True
245
246	6	def add(self, target):
247		"""Add self as a namespace under target."""
248	6	path, namespaces = self.__get_helper(target, self.path)
249	6	res = namespaces.setdefault(path, self)
250	6	if res is self:
251	6	self.parent_object = target
252
253	6	def set_if_none(self, name, value):
254		"""Set the attribute `name` to `value`, if it's initially None."""
255	6	if getattr(self, name) is None:
256	6	setattr(self, name, value)
257
258	6	def validate_assignment(self, name, scope):
		0 ignored issues – show Coding Style introduced 2016-11-26 17:09 UTC by Report Bug Copy Issue Report This method should have a docstring. The coding style of this project requires that you add a docstring to this code element. Below, you find an example for methods: class SomeClass: def some_method(self): """Do x and return foo.""" If you would like to know more about docstrings, we recommend to read PEP-257: Docstring Conventions. Loading history...
259	6	if name != self.name:
260	6	raise ValueError('Cannot rename namespace')
261	6	if scope is not self.scope:
262		# It should be possible to hit this line by assigning a namespace
263		# into another class. It may not be, however.
264		raise ValueError('Cannot reuse namespace')
265
266	6	def validate_parent(self, parent):
		0 ignored issues – show Coding Style introduced 2016-11-26 17:09 UTC by Report Bug Copy Issue Report This method should have a docstring. The coding style of this project requires that you add a docstring to this code element. Below, you find an example for methods: class SomeClass: def some_method(self): """Do x and return foo.""" If you would like to know more about docstrings, we recommend to read PEP-257: Docstring Conventions. Loading history...
267	6	if parent is not self.parent:
268		# This line can be hit by assigning a namespace into another
269		# namespace.
270	6	raise ValueError('Cannot reparent namespace')
271
272	6	def push(self, name, scope, parent):
273		"""Bind self to the given name and scope, and activate."""
274	6	self.set_if_none('name', name)
275	6	self.set_if_none('scope', scope)
276	6	self.set_if_none('parent', parent)
277	6	self.validate_assignment(name, scope)
278	6	self.validate_parent(parent)
279	6	self.scope.namespaces.append(self)
280	6	if self.needs_setup:
281	6	self.activate()
282
283	6	def activate(self):
284		"""Take over as the scope for the target."""
285	6	if self.active:
286	6	raise ValueError('Cannot double-activate.')
287	6	if self.scope is not None:
288	6	self.validate_parent(self.scope.dicts[0])
289	6	self.active = True
290	6	self.scope.dicts.insert(0, self)
291	6	self.needs_setup = False
292
293	6	def deactivate(self):
294		"""Stop being the scope for the target."""
295	6	if self.scope is not None and self.active:
296	6	self.active = False
297	6	self.scope.dicts.pop(0)
298
299	6	def __get__(self, instance, owner):
300	6	return _NamespaceProxy(self, instance, owner)
301
302	6	def __bool__(self):
		0 ignored issues – show Coding Style introduced 2016-11-26 17:09 UTC by Report Bug Copy Issue Report This method could be written as a function/class method. If a method does not access any attributes of the class, it could also be implemented as a function or static method. This can help improve readability. For example class Foo: def some_method(self, x, y): return x + y; could be written as class Foo: @classmethod def some_method(cls, x, y): return x + y; Loading history...
303		return True
304
305
306	6	class _NamespaceScope(collections.abc.MutableMapping):
307
308		"""The class creation namespace for _Namespaceables."""
309
310	6	__slots__ = 'dicts', 'namespaces', 'proxies', 'scope_proxy'
311
312	6	def __init__(self, dct):
313	6	self.dicts = [dct]
314	6	self.namespaces = []
315	6	self.proxies = proxies = weakref.WeakKeyDictionary()
316
317	6	class ScopeProxy(_ScopeProxy):
318
319		"""Local version of ScopeProxy for this scope."""
320
321	6	__slots__ = ()
322
323	6	def __init__(self, dct):
324	6	super().__init__(dct, proxies)
325
326	6	self.scope_proxy = ScopeProxy
327
328		# Mapping methods need to know about the dot syntax.
329		# Possibly namespaces themselves should know. Would simplify some things.
330
331	6	def __getitem__(self, key):
332	6	value = collections.ChainMap(*self.dicts)[key]
333	6	if isinstance(value, Namespace):
334	6	value = self.scope_proxy(value)
335	6	return value
336
337	6	def __setitem__(self, key, value):
338	6	dct = self.dicts[0]
339		# We just entered the context successfully.
340	6	if value is dct:
341	6	dct = self.dicts[1]
342	6	if isinstance(value, Namespace):
343	6	value.push(key, self, dct)
344	6	if isinstance(value, self.scope_proxy):
345	6	value = self.proxies[value]
346	6	value.validate_parent(dct)
347	6	value.validate_assignment(key, self)
348	6	if isinstance(value, (_ScopeProxy, _NamespaceProxy)):
349	6	raise ValueError('Cannot move scopes between classes.')
350	6	dct[key] = value
351
352	6	def __delitem__(self, key):
353	6	del self.dicts[0][key]
354
355		# These functions are incorrect and need to be rewritten.
356	6	def __iter__(self):
357		return iter(collections.ChainMap(*self.dicts))
358
359	6	def __len__(self):
360		return len(collections.ChainMap(*self.dicts))
361
362
363	6	_NAMESPACE_SCOPES = weakref.WeakKeyDictionary()
364
365
366	6	class _NamespaceBase:
367
368		"""Common base class for Namespaceable and its metaclass."""
369
370	6	__slots__ = ()
371
372		# Note: the dot format of invocation can "escape" self into other objects.
373		# This is not intended behavior, and the result of using dots "too deeply"
374		# should be considered undefined.
375		# I would like it to be an error, if I can figure out how.
376
377	6	@staticmethod
378		def __is_proxy(value):
		0 ignored issues – show Coding Style introduced 2016-11-25 16:00 UTC by Report Bug Copy Issue Report This method should have a docstring. The coding style of this project requires that you add a docstring to this code element. Below, you find an example for methods: class SomeClass: def some_method(self): """Do x and return foo.""" If you would like to know more about docstrings, we recommend to read PEP-257: Docstring Conventions. Loading history...
379	6	if not isinstance(value, _NamespaceProxy):
380		# This line can be hit by doing what the error message says.
381	6	raise ValueError('Given a dot attribute that went too deep.')
382	6	return value
383
384	6	def __getattribute__(self, name):
385	6	parent, is_namespace, name_ = name.rpartition('.')
386	6	if is_namespace:
387	6	self_ = self
388	6	for element in parent.split('.'):
389	6	self_ = self.__is_proxy(getattr(self_, element))
390	6	return getattr(getattr(self, parent), name_)
391	6	return super(_NamespaceBase, type(self)).__getattribute__(self, name)
392
393	6	def __setattr__(self, name, value):
394	6	parent, is_namespace, name_ = name.rpartition('.')
395	6	if is_namespace:
396	6	setattr(self.__is_proxy(getattr(self, parent)), name_, value)
397	6	return
398	6	super(_NamespaceBase, type(self)).__setattr__(self, name, value)
399
400	6	def __delattr__(self, name):
401	6	parent, is_namespace, name_ = name.rpartition('.')
402	6	if is_namespace:
403	6	delattr(self.__is_proxy(getattr(self, parent)), name_)
404	6	return
405		# This line can be hit by deleting an attribute that isn't a namespace.
406	6	super(_NamespaceBase, type(self)).__delattr__(self, name)
407
408
409	6	class _Namespaceable(_NamespaceBase, type):
410
411		"""Metaclass for classes that can contain namespaces.
412
413		Using the metaclass directly is a bad idea. Use a base class instead.
414		"""
415
416	6	@classmethod
417		def __prepare__(mcs, name, bases, **kwargs):
418	6	return _NamespaceScope(super().__prepare__(name, bases, **kwargs))
419
420	6	def __new__(mcs, name, bases, dct, **kwargs):
421	6	cls = super().__new__(mcs, name, bases, dct.dicts[0], **kwargs)
422	6	if _DEFINED and not issubclass(cls, Namespaceable):
423		# This line can be hit with class(metaclass=type(Namespaceable)):
424	6	raise ValueError(
425		'Cannot create a _Namespaceable that does not inherit from '
426		'Namespaceable')
427	6	_NAMESPACE_SCOPES[cls] = dct
428	6	for namespace in dct.namespaces:
429	6	namespace.add(cls)
430	6	if ENABLE_SET_NAME:
431	2	for name, value in namespace.items():
432	2	wrapped = _DescriptorInspector(value)
433	2	if wrapped.has_set_name:
434	2	wrapped.set_name(cls, name)
435	6	return cls
436
437	6	def __setattr__(cls, name, value):
438	6	if (
439		'.' not in name and isinstance(value, Namespace) and
440		value.name != name):
441	6	scope = _NAMESPACE_SCOPES[cls]
442	6	value.push(name, scope, scope.dicts[-1])
443	6	value.add(cls)
444	6	super(_Namespaceable, type(cls)).__setattr__(cls, name, value)
445
446
447	6	_DEFINED = False
448
449
450	6	class Namespaceable(_NamespaceBase, metaclass=_Namespaceable):
451
452		"""Base class for classes that can contain namespaces.
453
454		A note for people extending the functionality:
455		The base class for Namespaceable and its metaclass uses a non-standard
456		super() invocation in its definitions of several methods. This was the only
457		way I could find to mitigate some bugs I encountered with a standard
458		invocation. If you override any of methods defined on built-in types, I
459		recommend this form for maximal reusability:
460
461		super(class, type(self)).__method__(self, ...)
462
463		This avoids confusing error messages in case self is a subclass of class,
464		in addition to being an instance.
465
466		If you're not delegating above Namespaceable, you can probably use the
467		standard invocation, unless you bring about the above situation on your own
468		types.
469		"""
470
471
472		_DEFINED = True
473

mwchase / class-namespaces

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