_Namespaceable.__prepare__() - Code Metrics - Inspection of "Updated readme." - mwchase/class-namespaces - Measure and Improve Code Quality continuously with Scrutinizer

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by Max

created 2016-11-21 21:48 UTC

_Namespaceable.prepare() A

↳ Parent: _Namespaceable

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


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:
            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:
            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'

    __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

    @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

    def __setitem__(self, key, value):
        if (
                self.parent_object is not None and
                isinstance(value, Namespace) and value.name != key):
            value.push(key, self.scope)
            value.add(self.parent_object)
        super().__setitem__(key, value)

    def __enter__(self):
        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:
            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, dct, cls_):
        """Return False if there's a non-Namespace object in the path."""
        try:
            namespace = vars(cls_)
            for name in dct.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 push(self, name, scope):
        """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', scope.dicts[0])
        if name != self.name:
            raise ValueError('Cannot rename namespace')
        if scope is not self.scope:
            raise ValueError('Cannot reuse namespace')
        if scope.dicts[0] is not self.parent:
            raise ValueError('Cannot reparent namespace')
        self.scope.namespaces.append(self)
        self.activate()

    def activate(self):
        """Take over as the scope for the target."""
        if self.scope is not None and not self.active:
            if self.scope.dicts[0] is not self.parent:
                raise ValueError('Cannot reparent namespace')
            self.active = True
            self.scope.dicts.insert(0, self)

    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)


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

    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]
        if isinstance(value, self.scope_proxy):
            value = self.proxies[value]
        if isinstance(value, Namespace) and value.name != key:
            value.push(key, self)
        dct[key] = value

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

    def __iter__(self):
        return iter(collections.ChainMap(*self.dicts))

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


_NAMESPACE_SCOPES = weakref.WeakKeyDictionary()


class _Namespaceable(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)
        _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 isinstance(value, Namespace) and value.name != name:
            value.push(name, _NAMESPACE_SCOPES[cls])
            value.add(cls)
        if issubclass(cls, _Namespaceable):
            super().__setattr__(cls, name, value)
        else:
            super().__setattr__(name, value)


class Namespaceable(metaclass=_Namespaceable):

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


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, dct):
26		"""Return a chained map of lookups for the given namespace and mro."""
27	6	return collections.ChainMap(*[
28		Namespace.get_namespace(cls, dct.path) for cls in
29		itertools.takewhile(
30		functools.partial(Namespace.no_blocker, dct),
31		(cls for cls in mro if isinstance(cls, _Namespaceable))) if
32		Namespace.namespace_exists(dct.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)
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	mro = mro[mro.index(dct.parent_object):]
52	6	return _mro_to_chained(mro, dct)
53
54
55	6	def _retarget(ns_proxy):
56		"""Convert a class lookup to an instance lookup, if needed."""
57	6	dct, instance, owner = _PROXY_INFOS[ns_proxy]
58	6	if instance is None and isinstance(type(owner), _Namespaceable):
59	6	instance, owner = owner, type(owner)
60	6	dct = Namespace.get_namespace(owner, dct.path)
61	6	ns_proxy = _NamespaceProxy(dct, instance, owner)
62	6	return ns_proxy
63
64
65	6	class _NamespaceProxy(_Proxy):
66
67		"""Proxy object for manipulating and querying namespaces."""
68
69	6	__slots__ = '__weakref__',
70
71	6	def __init__(self, dct, instance, owner):
72	6	_PROXY_INFOS[self] = dct, instance, owner
73
74	6	def __dir__(self):
75	6	return collections.ChainMap(_instance_map(self), _mro_map(self))
76
77	6	def __getattribute__(self, name):
78	6	self = _retarget(self)
79	6	_, instance, owner = _PROXY_INFOS[self]
80	6	instance_map = _instance_map(self)
81	6	mro_map = _mro_map(self)
82	6	instance_value = ops.get(instance_map, name)
83	6	mro_value = ops.get(mro_map, name)
84	6	if ops.is_data(mro_value):
85	6	return mro_value.get(instance, owner)
86	6	elif issubclass(owner, type) and ops.has_get(instance_value):
87	6	return instance_value.get(None, instance)
88	6	elif instance_value is not None:
89	6	return instance_value.object
90	6	elif ops.has_get(mro_value):
91	6	return mro_value.get(instance, owner)
92	6	elif mro_value is not None:
93	6	return mro_value.object
94		else:
95	6	raise AttributeError(name)
96
97	6	def __setattr__(self, name, value):
98	6	self = _retarget(self)
99	6	dct, instance, owner = _PROXY_INFOS[self]
100	6	if instance is None:
101	6	real_map = Namespace.get_namespace(owner, dct.path)
102	6	real_map[name] = value
103	6	return
104	6	mro_map = _mro_map(self)
105	6	target_value = ops.get_data(mro_map, name)
106	6	if target_value is not None:
107		target_value.set(instance, value)
108		return
109	6	instance_map = Namespace.get_namespace(instance, dct.path)
110	6	instance_map[name] = value
111
112	6	def __delattr__(self, name):
113	6	self = _retarget(self)
114	6	dct, instance, owner = _PROXY_INFOS[self]
115	6	real_map = Namespace.get_namespace(owner, dct.path)
116	6	if instance is None:
117	6	ops.delete(real_map, name)
118	6	return
119	6	value = ops.get_data(real_map, name)
120	6	if value is not None:
121		value.delete(instance)
122		return
123	6	instance_map = Namespace.get_namespace(instance, dct.path)
124	6	ops.delete(instance_map, name)
125
126
127	6	class Namespace(dict):
128
129		"""Namespace."""
130
131	6	__slots__ = 'name', 'scope', 'parent', 'active', 'parent_object'
132
133	6	__namespaces = {}
134
135	6	def __init__(self, args, *kwargs):
136	6	super().__init__(args, *kwargs)
137	6	bad_values = tuple(
138		value for value in self.values() if
139		isinstance(value, (Namespace, _Proxy)))
140	6	if bad_values:
141	6	raise ValueError('Bad values: {}'.format(bad_values))
142	6	self.name = None
143	6	self.scope = None
144	6	self.parent = None
145	6	self.active = False
146	6	self.parent_object = None
147
148	6	@classmethod
149		def premake(cls, name, parent):
150		"""Return an empty namespace with the given name and parent."""
151	6	self = cls()
152	6	self.name = name
153	6	self.parent = parent
154	6	return self
155
156	6	def __setitem__(self, key, value):
157	6	if (
158		self.parent_object is not None and
159		isinstance(value, Namespace) and value.name != key):
160	6	value.push(key, self.scope)
161	6	value.add(self.parent_object)
162	6	super().__setitem__(key, value)
163
164	6	def __enter__(self):
165	6	self.activate()
166	6	return self
167
168	6	def __exit__(self, exc_type, exc_value, traceback):
169	6	if self.name is None:
170	6	raise RuntimeError('Namespace must be named.')
171	6	self.deactivate()
172
173	6	@property
174		def path(self):
175		"""Return the full path of the namespace."""
176	6	if self.name is None or self.parent is None:
177		raise ValueError
178	6	if isinstance(self.parent, Namespace):
179	6	parent_path = self.parent.path
180		else:
181	6	parent_path = ()
182	6	return parent_path + (self.name,)
183
184	6	@classmethod
185		def __get_helper(cls, target, path):
186		"""Return the namespace for `target` at `path`, create if needed."""
187	6	if isinstance(target, _Namespaceable):
188	6	path_ = target, path
189	6	namespaces = cls.__namespaces
190		else:
191	6	path_ = path
192	6	try:
193	6	namespaces = target.__namespaces
194	6	except AttributeError:
195	6	namespaces = {}
196	6	target.__namespaces = namespaces
197	6	return path_, namespaces
198
199	6	@classmethod
200		def namespace_exists(cls, path, target):
201		"""Return whether the given namespace exists."""
202	6	path_, namespaces = cls.__get_helper(target, path)
203	6	return path_ in namespaces
204
205	6	@classmethod
206		def get_namespace(cls, target, path):
207		"""Return a namespace with given target and path, create if needed."""
208	6	path_, namespaces = cls.__get_helper(target, path)
209	6	try:
210	6	return namespaces[path_]
211	6	except KeyError:
212	6	if len(path) == 1:
213	6	parent = {}
214		else:
215	6	parent = cls.get_namespace(target, path[:-1])
216	6	return namespaces.setdefault(path_, cls.premake(path[-1], parent))
217
218	6	@classmethod
219		def no_blocker(cls, dct, cls_):
220		"""Return False if there's a non-Namespace object in the path."""
221	6	try:
222	6	namespace = vars(cls_)
223	6	for name in dct.path:
224	6	namespace = namespace[name]
225	6	if not isinstance(namespace, cls):
226	6	return False
227	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...
228	6	pass
229	6	return True
230
231	6	def add(self, target):
232		"""Add self as a namespace under target."""
233	6	path, namespaces = self.__get_helper(target, self.path)
234	6	res = namespaces.setdefault(path, self)
235	6	if res is self:
236	6	self.parent_object = target
237
238	6	def set_if_none(self, name, value):
239		"""Set the attribute `name` to `value`, if it's initially None."""
240	6	if getattr(self, name) is None:
241	6	setattr(self, name, value)
242
243	6	def push(self, name, scope):
244		"""Bind self to the given name and scope, and activate."""
245	6	self.set_if_none('name', name)
246	6	self.set_if_none('scope', scope)
247	6	self.set_if_none('parent', scope.dicts[0])
248	6	if name != self.name:
249	6	raise ValueError('Cannot rename namespace')
250	6	if scope is not self.scope:
251		raise ValueError('Cannot reuse namespace')
252	6	if scope.dicts[0] is not self.parent:
253		raise ValueError('Cannot reparent namespace')
254	6	self.scope.namespaces.append(self)
255	6	self.activate()
256
257	6	def activate(self):
258		"""Take over as the scope for the target."""
259	6	if self.scope is not None and not self.active:
260	6	if self.scope.dicts[0] is not self.parent:
261		raise ValueError('Cannot reparent namespace')
262	6	self.active = True
263	6	self.scope.dicts.insert(0, self)
264
265	6	def deactivate(self):
266		"""Stop being the scope for the target."""
267	6	if self.scope is not None and self.active:
268	6	self.active = False
269	6	self.scope.dicts.pop(0)
270
271	6	def __get__(self, instance, owner):
272	6	return _NamespaceProxy(self, instance, owner)
273
274
275	6	class _NamespaceScope(collections.abc.MutableMapping):
276
277		"""The class creation namespace for _Namespaceables."""
278
279	6	__slots__ = 'dicts', 'namespaces', 'proxies', 'scope_proxy'
280
281	6	def __init__(self, dct):
282	6	self.dicts = [dct]
283	6	self.namespaces = []
284	6	self.proxies = proxies = weakref.WeakKeyDictionary()
285
286	6	class ScopeProxy(_ScopeProxy):
287
288		"""Local version of ScopeProxy for this scope."""
289
290	6	__slots__ = ()
291
292	6	def __init__(self, dct):
293	6	super().__init__(dct, proxies)
294
295	6	self.scope_proxy = ScopeProxy
296
297	6	def __getitem__(self, key):
298	6	value = collections.ChainMap(*self.dicts)[key]
299	6	if isinstance(value, Namespace):
300	6	value = self.scope_proxy(value)
301	6	return value
302
303	6	def __setitem__(self, key, value):
304	6	dct = self.dicts[0]
305	6	if isinstance(value, self.scope_proxy):
306	6	value = self.proxies[value]
307	6	if isinstance(value, Namespace) and value.name != key:
308	6	value.push(key, self)
309	6	dct[key] = value
310
311	6	def __delitem__(self, key):
312	6	del self.dicts[0][key]
313
314	6	def __iter__(self):
315		return iter(collections.ChainMap(*self.dicts))
316
317	6	def __len__(self):
318		return len(collections.ChainMap(*self.dicts))
319
320
321	6	_NAMESPACE_SCOPES = weakref.WeakKeyDictionary()
322
323
324	6	class _Namespaceable(type):
325
326		"""Metaclass for classes that can contain namespaces.
327
328		Using the metaclass directly is a bad idea. Use a base class instead.
329		"""
330
331	6	@classmethod
332		def __prepare__(mcs, name, bases, **kwargs):
333	6	return _NamespaceScope(super().__prepare__(name, bases, **kwargs))
334
335	6	def __new__(mcs, name, bases, dct, **kwargs):
336	6	cls = super().__new__(mcs, name, bases, dct.dicts[0], **kwargs)
337	6	_NAMESPACE_SCOPES[cls] = dct
338	6	for namespace in dct.namespaces:
339	6	namespace.add(cls)
340	6	if ENABLE_SET_NAME:
341	2	for name, value in namespace.items():
342	2	wrapped = _DescriptorInspector(value)
343	2	if wrapped.has_set_name:
344	2	wrapped.set_name(cls, name)
345	6	return cls
346
347	6	def __setattr__(cls, name, value):
348	6	if isinstance(value, Namespace) and value.name != name:
349	6	value.push(name, _NAMESPACE_SCOPES[cls])
350	6	value.add(cls)
351	6	if issubclass(cls, _Namespaceable):
352	6	super().__setattr__(cls, name, value)
353		else:
354	6	super().__setattr__(name, value)
355
356
357	6	class Namespaceable(metaclass=_Namespaceable):
358
359		"""Base class for classes that can contain namespaces."""
360

mwchase / class-namespaces

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