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1##############################################################################
2# Copyright (c) 2003 Zope Foundation and Contributors.
3# All Rights Reserved.
4#
5# This software is subject to the provisions of the Zope Public License,
6# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
7# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
8# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
9# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
10# FOR A PARTICULAR PURPOSE.
11##############################################################################
12"""Implementation of interface declarations
14There are three flavors of declarations:
16 - Declarations are used to simply name declared interfaces.
18 - ImplementsDeclarations are used to express the interfaces that a
19 class implements (that instances of the class provides).
21 Implements specifications support inheriting interfaces.
23 - ProvidesDeclarations are used to express interfaces directly
24 provided by objects.
26"""
27__docformat__ = 'restructuredtext'
29import sys
30from types import FunctionType
31from types import MethodType
32from types import ModuleType
33import weakref
35from zope.interface.advice import addClassAdvisor
36from zope.interface.interface import Interface
37from zope.interface.interface import InterfaceClass
38from zope.interface.interface import SpecificationBase
39from zope.interface.interface import Specification
40from zope.interface.interface import NameAndModuleComparisonMixin
41from zope.interface._compat import CLASS_TYPES as DescriptorAwareMetaClasses
42from zope.interface._compat import PYTHON3
43from zope.interface._compat import _use_c_impl
45__all__ = [
46 # None. The public APIs of this module are
47 # re-exported from zope.interface directly.
48]
50# pylint:disable=too-many-lines
52# Registry of class-implementation specifications
53BuiltinImplementationSpecifications = {}
55_ADVICE_ERROR = ('Class advice impossible in Python3. '
56 'Use the @%s class decorator instead.')
58_ADVICE_WARNING = ('The %s API is deprecated, and will not work in Python3 '
59 'Use the @%s class decorator instead.')
61def _next_super_class(ob):
62 # When ``ob`` is an instance of ``super``, return
63 # the next class in the MRO that we should actually be
64 # looking at. Watch out for diamond inheritance!
65 self_class = ob.__self_class__
66 class_that_invoked_super = ob.__thisclass__
67 complete_mro = self_class.__mro__
68 next_class = complete_mro[complete_mro.index(class_that_invoked_super) + 1]
69 return next_class
71class named(object):
73 def __init__(self, name):
74 self.name = name
76 def __call__(self, ob):
77 ob.__component_name__ = self.name
78 return ob
81class Declaration(Specification):
82 """Interface declarations"""
84 __slots__ = ()
86 def __init__(self, *bases):
87 Specification.__init__(self, _normalizeargs(bases))
89 def __contains__(self, interface):
90 """Test whether an interface is in the specification
91 """
93 return self.extends(interface) and interface in self.interfaces()
95 def __iter__(self):
96 """Return an iterator for the interfaces in the specification
97 """
98 return self.interfaces()
100 def flattened(self):
101 """Return an iterator of all included and extended interfaces
102 """
103 return iter(self.__iro__)
105 def __sub__(self, other):
106 """Remove interfaces from a specification
107 """
108 return Declaration(*[
109 i for i in self.interfaces()
110 if not [
111 j
112 for j in other.interfaces()
113 if i.extends(j, 0) # non-strict extends
114 ]
115 ])
117 def __add__(self, other):
118 """
119 Add two specifications or a specification and an interface
120 and produce a new declaration.
122 .. versionchanged:: 5.4.0
123 Now tries to preserve a consistent resolution order. Interfaces
124 being added to this object are added to the front of the resulting resolution
125 order if they already extend an interface in this object. Previously,
126 they were always added to the end of the order, which easily resulted in
127 invalid orders.
128 """
129 before = []
130 result = list(self.interfaces())
131 seen = set(result)
132 for i in other.interfaces():
133 if i in seen:
134 continue
135 seen.add(i)
136 if any(i.extends(x) for x in result):
137 # It already extends us, e.g., is a subclass,
138 # so it needs to go at the front of the RO.
139 before.append(i)
140 else:
141 result.append(i)
142 return Declaration(*(before + result))
144 # XXX: Is __radd__ needed? No tests break if it's removed.
145 # If it is needed, does it need to handle the C3 ordering differently?
146 # I (JAM) don't *think* it does.
147 __radd__ = __add__
149 @staticmethod
150 def _add_interfaces_to_cls(interfaces, cls):
151 # Strip redundant interfaces already provided
152 # by the cls so we don't produce invalid
153 # resolution orders.
154 implemented_by_cls = implementedBy(cls)
155 interfaces = tuple([
156 iface
157 for iface in interfaces
158 if not implemented_by_cls.isOrExtends(iface)
159 ])
160 return interfaces + (implemented_by_cls,)
162 @staticmethod
163 def _argument_names_for_repr(interfaces):
164 # These don't actually have to be interfaces, they could be other
165 # Specification objects like Implements. Also, the first
166 # one is typically/nominally the cls.
167 ordered_names = []
168 names = set()
169 for iface in interfaces:
170 duplicate_transform = repr
171 if isinstance(iface, InterfaceClass):
172 # Special case to get 'foo.bar.IFace'
173 # instead of '<InterfaceClass foo.bar.IFace>'
174 this_name = iface.__name__
175 duplicate_transform = str
176 elif isinstance(iface, type):
177 # Likewise for types. (Ignoring legacy old-style
178 # classes.)
179 this_name = iface.__name__
180 duplicate_transform = _implements_name
181 elif (isinstance(iface, Implements)
182 and not iface.declared
183 and iface.inherit in interfaces):
184 # If nothing is declared, there's no need to even print this;
185 # it would just show as ``classImplements(Class)``, and the
186 # ``Class`` has typically already.
187 continue
188 else:
189 this_name = repr(iface)
191 already_seen = this_name in names
192 names.add(this_name)
193 if already_seen:
194 this_name = duplicate_transform(iface)
196 ordered_names.append(this_name)
197 return ', '.join(ordered_names)
200class _ImmutableDeclaration(Declaration):
201 # A Declaration that is immutable. Used as a singleton to
202 # return empty answers for things like ``implementedBy``.
203 # We have to define the actual singleton after normalizeargs
204 # is defined, and that in turn is defined after InterfaceClass and
205 # Implements.
207 __slots__ = ()
209 __instance = None
211 def __new__(cls):
212 if _ImmutableDeclaration.__instance is None:
213 _ImmutableDeclaration.__instance = object.__new__(cls)
214 return _ImmutableDeclaration.__instance
216 def __reduce__(self):
217 return "_empty"
219 @property
220 def __bases__(self):
221 return ()
223 @__bases__.setter
224 def __bases__(self, new_bases):
225 # We expect the superclass constructor to set ``self.__bases__ = ()``.
226 # Rather than attempt to special case that in the constructor and allow
227 # setting __bases__ only at that time, it's easier to just allow setting
228 # the empty tuple at any time. That makes ``x.__bases__ = x.__bases__`` a nice
229 # no-op too. (Skipping the superclass constructor altogether is a recipe
230 # for maintenance headaches.)
231 if new_bases != ():
232 raise TypeError("Cannot set non-empty bases on shared empty Declaration.")
234 # As the immutable empty declaration, we cannot be changed.
235 # This means there's no logical reason for us to have dependents
236 # or subscriptions: we'll never notify them. So there's no need for
237 # us to keep track of any of that.
238 @property
239 def dependents(self):
240 return {}
242 changed = subscribe = unsubscribe = lambda self, _ignored: None
244 def interfaces(self):
245 # An empty iterator
246 return iter(())
248 def extends(self, interface, strict=True):
249 return interface is self._ROOT
251 def get(self, name, default=None):
252 return default
254 def weakref(self, callback=None):
255 # We're a singleton, we never go away. So there's no need to return
256 # distinct weakref objects here; their callbacks will never
257 # be called. Instead, we only need to return a callable that
258 # returns ourself. The easiest one is to return _ImmutableDeclaration
259 # itself; testing on Python 3.8 shows that's faster than a function that
260 # returns _empty. (Remember, one goal is to avoid allocating any
261 # object, and that includes a method.)
262 return _ImmutableDeclaration
264 @property
265 def _v_attrs(self):
266 # _v_attrs is not a public, documented property, but some client
267 # code uses it anyway as a convenient place to cache things. To keep
268 # the empty declaration truly immutable, we must ignore that. That includes
269 # ignoring assignments as well.
270 return {}
272 @_v_attrs.setter
273 def _v_attrs(self, new_attrs):
274 pass
277##############################################################################
278#
279# Implementation specifications
280#
281# These specify interfaces implemented by instances of classes
283class Implements(NameAndModuleComparisonMixin,
284 Declaration):
285 # Inherit from NameAndModuleComparisonMixin to be
286 # mutually comparable with InterfaceClass objects.
287 # (The two must be mutually comparable to be able to work in e.g., BTrees.)
288 # Instances of this class generally don't have a __module__ other than
289 # `zope.interface.declarations`, whereas they *do* have a __name__ that is the
290 # fully qualified name of the object they are representing.
292 # Note, though, that equality and hashing are still identity based. This
293 # accounts for things like nested objects that have the same name (typically
294 # only in tests) and is consistent with pickling. As far as comparisons to InterfaceClass
295 # goes, we'll never have equal name and module to those, so we're still consistent there.
296 # Instances of this class are essentially intended to be unique and are
297 # heavily cached (note how our __reduce__ handles this) so having identity
298 # based hash and eq should also work.
300 # We want equality and hashing to be based on identity. However, we can't actually
301 # implement __eq__/__ne__ to do this because sometimes we get wrapped in a proxy.
302 # We need to let the proxy types implement these methods so they can handle unwrapping
303 # and then rely on: (1) the interpreter automatically changing `implements == proxy` into
304 # `proxy == implements` (which will call proxy.__eq__ to do the unwrapping) and then
305 # (2) the default equality and hashing semantics being identity based.
307 # class whose specification should be used as additional base
308 inherit = None
310 # interfaces actually declared for a class
311 declared = ()
313 # Weak cache of {class: <implements>} for super objects.
314 # Created on demand. These are rare, as of 5.0 anyway. Using a class
315 # level default doesn't take space in instances. Using _v_attrs would be
316 # another place to store this without taking space unless needed.
317 _super_cache = None
319 __name__ = '?'
321 @classmethod
322 def named(cls, name, *bases):
323 # Implementation method: Produce an Implements interface with
324 # a fully fleshed out __name__ before calling the constructor, which
325 # sets bases to the given interfaces and which may pass this object to
326 # other objects (e.g., to adjust dependents). If they're sorting or comparing
327 # by name, this needs to be set.
328 inst = cls.__new__(cls)
329 inst.__name__ = name
330 inst.__init__(*bases)
331 return inst
333 def changed(self, originally_changed):
334 try:
335 del self._super_cache
336 except AttributeError:
337 pass
338 return super(Implements, self).changed(originally_changed)
340 def __repr__(self):
341 if self.inherit:
342 name = getattr(self.inherit, '__name__', None) or _implements_name(self.inherit)
343 else:
344 name = self.__name__
345 declared_names = self._argument_names_for_repr(self.declared)
346 if declared_names:
347 declared_names = ', ' + declared_names
348 return 'classImplements(%s%s)' % (name, declared_names)
350 def __reduce__(self):
351 return implementedBy, (self.inherit, )
354def _implements_name(ob):
355 # Return the __name__ attribute to be used by its __implemented__
356 # property.
357 # This must be stable for the "same" object across processes
358 # because it is used for sorting. It needn't be unique, though, in cases
359 # like nested classes named Foo created by different functions, because
360 # equality and hashing is still based on identity.
361 # It might be nice to use __qualname__ on Python 3, but that would produce
362 # different values between Py2 and Py3.
363 return (getattr(ob, '__module__', '?') or '?') + \
364 '.' + (getattr(ob, '__name__', '?') or '?')
367def _implementedBy_super(sup):
368 # TODO: This is now simple enough we could probably implement
369 # in C if needed.
371 # If the class MRO is strictly linear, we could just
372 # follow the normal algorithm for the next class in the
373 # search order (e.g., just return
374 # ``implemented_by_next``). But when diamond inheritance
375 # or mixins + interface declarations are present, we have
376 # to consider the whole MRO and compute a new Implements
377 # that excludes the classes being skipped over but
378 # includes everything else.
379 implemented_by_self = implementedBy(sup.__self_class__)
380 cache = implemented_by_self._super_cache # pylint:disable=protected-access
381 if cache is None:
382 cache = implemented_by_self._super_cache = weakref.WeakKeyDictionary()
384 key = sup.__thisclass__
385 try:
386 return cache[key]
387 except KeyError:
388 pass
390 next_cls = _next_super_class(sup)
391 # For ``implementedBy(cls)``:
392 # .__bases__ is .declared + [implementedBy(b) for b in cls.__bases__]
393 # .inherit is cls
395 implemented_by_next = implementedBy(next_cls)
396 mro = sup.__self_class__.__mro__
397 ix_next_cls = mro.index(next_cls)
398 classes_to_keep = mro[ix_next_cls:]
399 new_bases = [implementedBy(c) for c in classes_to_keep]
401 new = Implements.named(
402 implemented_by_self.__name__ + ':' + implemented_by_next.__name__,
403 *new_bases
404 )
405 new.inherit = implemented_by_next.inherit
406 new.declared = implemented_by_next.declared
407 # I don't *think* that new needs to subscribe to ``implemented_by_self``;
408 # it auto-subscribed to its bases, and that should be good enough.
409 cache[key] = new
411 return new
414@_use_c_impl
415def implementedBy(cls): # pylint:disable=too-many-return-statements,too-many-branches
416 """Return the interfaces implemented for a class' instances
418 The value returned is an `~zope.interface.interfaces.IDeclaration`.
419 """
420 try:
421 if isinstance(cls, super):
422 # Yes, this needs to be inside the try: block. Some objects
423 # like security proxies even break isinstance.
424 return _implementedBy_super(cls)
426 spec = cls.__dict__.get('__implemented__')
427 except AttributeError:
429 # we can't get the class dict. This is probably due to a
430 # security proxy. If this is the case, then probably no
431 # descriptor was installed for the class.
433 # We don't want to depend directly on zope.security in
434 # zope.interface, but we'll try to make reasonable
435 # accommodations in an indirect way.
437 # We'll check to see if there's an implements:
439 spec = getattr(cls, '__implemented__', None)
440 if spec is None:
441 # There's no spec stred in the class. Maybe its a builtin:
442 spec = BuiltinImplementationSpecifications.get(cls)
443 if spec is not None:
444 return spec
445 return _empty
447 if spec.__class__ == Implements:
448 # we defaulted to _empty or there was a spec. Good enough.
449 # Return it.
450 return spec
452 # TODO: need old style __implements__ compatibility?
453 # Hm, there's an __implemented__, but it's not a spec. Must be
454 # an old-style declaration. Just compute a spec for it
455 return Declaration(*_normalizeargs((spec, )))
457 if isinstance(spec, Implements):
458 return spec
460 if spec is None:
461 spec = BuiltinImplementationSpecifications.get(cls)
462 if spec is not None:
463 return spec
465 # TODO: need old style __implements__ compatibility?
466 spec_name = _implements_name(cls)
467 if spec is not None:
468 # old-style __implemented__ = foo declaration
469 spec = (spec, ) # tuplefy, as it might be just an int
470 spec = Implements.named(spec_name, *_normalizeargs(spec))
471 spec.inherit = None # old-style implies no inherit
472 del cls.__implemented__ # get rid of the old-style declaration
473 else:
474 try:
475 bases = cls.__bases__
476 except AttributeError:
477 if not callable(cls):
478 raise TypeError("ImplementedBy called for non-factory", cls)
479 bases = ()
481 spec = Implements.named(spec_name, *[implementedBy(c) for c in bases])
482 spec.inherit = cls
484 try:
485 cls.__implemented__ = spec
486 if not hasattr(cls, '__providedBy__'):
487 cls.__providedBy__ = objectSpecificationDescriptor
489 if (isinstance(cls, DescriptorAwareMetaClasses)
490 and '__provides__' not in cls.__dict__):
491 # Make sure we get a __provides__ descriptor
492 cls.__provides__ = ClassProvides(
493 cls,
494 getattr(cls, '__class__', type(cls)),
495 )
497 except TypeError:
498 if not isinstance(cls, type):
499 raise TypeError("ImplementedBy called for non-type", cls)
500 BuiltinImplementationSpecifications[cls] = spec
502 return spec
505def classImplementsOnly(cls, *interfaces):
506 """
507 Declare the only interfaces implemented by instances of a class
509 The arguments after the class are one or more interfaces or interface
510 specifications (`~zope.interface.interfaces.IDeclaration` objects).
512 The interfaces given (including the interfaces in the specifications)
513 replace any previous declarations, *including* inherited definitions. If you
514 wish to preserve inherited declarations, you can pass ``implementedBy(cls)``
515 in *interfaces*. This can be used to alter the interface resolution order.
516 """
517 spec = implementedBy(cls)
518 # Clear out everything inherited. It's important to
519 # also clear the bases right now so that we don't improperly discard
520 # interfaces that are already implemented by *old* bases that we're
521 # about to get rid of.
522 spec.declared = ()
523 spec.inherit = None
524 spec.__bases__ = ()
525 _classImplements_ordered(spec, interfaces, ())
528def classImplements(cls, *interfaces):
529 """
530 Declare additional interfaces implemented for instances of a class
532 The arguments after the class are one or more interfaces or
533 interface specifications (`~zope.interface.interfaces.IDeclaration` objects).
535 The interfaces given (including the interfaces in the specifications)
536 are added to any interfaces previously declared. An effort is made to
537 keep a consistent C3 resolution order, but this cannot be guaranteed.
539 .. versionchanged:: 5.0.0
540 Each individual interface in *interfaces* may be added to either the
541 beginning or end of the list of interfaces declared for *cls*,
542 based on inheritance, in order to try to maintain a consistent
543 resolution order. Previously, all interfaces were added to the end.
544 .. versionchanged:: 5.1.0
545 If *cls* is already declared to implement an interface (or derived interface)
546 in *interfaces* through inheritance, the interface is ignored. Previously, it
547 would redundantly be made direct base of *cls*, which often produced inconsistent
548 interface resolution orders. Now, the order will be consistent, but may change.
549 Also, if the ``__bases__`` of the *cls* are later changed, the *cls* will no
550 longer be considered to implement such an interface (changing the ``__bases__`` of *cls*
551 has never been supported).
552 """
553 spec = implementedBy(cls)
554 interfaces = tuple(_normalizeargs(interfaces))
556 before = []
557 after = []
559 # Take steps to try to avoid producing an invalid resolution
560 # order, while still allowing for BWC (in the past, we always
561 # appended)
562 for iface in interfaces:
563 for b in spec.declared:
564 if iface.extends(b):
565 before.append(iface)
566 break
567 else:
568 after.append(iface)
569 _classImplements_ordered(spec, tuple(before), tuple(after))
572def classImplementsFirst(cls, iface):
573 """
574 Declare that instances of *cls* additionally provide *iface*.
576 The second argument is an interface or interface specification.
577 It is added as the highest priority (first in the IRO) interface;
578 no attempt is made to keep a consistent resolution order.
580 .. versionadded:: 5.0.0
581 """
582 spec = implementedBy(cls)
583 _classImplements_ordered(spec, (iface,), ())
586def _classImplements_ordered(spec, before=(), after=()):
587 # Elide everything already inherited.
588 # Except, if it is the root, and we don't already declare anything else
589 # that would imply it, allow the root through. (TODO: When we disallow non-strict
590 # IRO, this part of the check can be removed because it's not possible to re-declare
591 # like that.)
592 before = [
593 x
594 for x in before
595 if not spec.isOrExtends(x) or (x is Interface and not spec.declared)
596 ]
597 after = [
598 x
599 for x in after
600 if not spec.isOrExtends(x) or (x is Interface and not spec.declared)
601 ]
603 # eliminate duplicates
604 new_declared = []
605 seen = set()
606 for l in before, spec.declared, after:
607 for b in l:
608 if b not in seen:
609 new_declared.append(b)
610 seen.add(b)
612 spec.declared = tuple(new_declared)
614 # compute the bases
615 bases = new_declared # guaranteed no dupes
617 if spec.inherit is not None:
618 for c in spec.inherit.__bases__:
619 b = implementedBy(c)
620 if b not in seen:
621 seen.add(b)
622 bases.append(b)
624 spec.__bases__ = tuple(bases)
627def _implements_advice(cls):
628 interfaces, do_classImplements = cls.__dict__['__implements_advice_data__']
629 del cls.__implements_advice_data__
630 do_classImplements(cls, *interfaces)
631 return cls
634class implementer(object):
635 """
636 Declare the interfaces implemented by instances of a class.
638 This function is called as a class decorator.
640 The arguments are one or more interfaces or interface
641 specifications (`~zope.interface.interfaces.IDeclaration`
642 objects).
644 The interfaces given (including the interfaces in the
645 specifications) are added to any interfaces previously declared,
646 unless the interface is already implemented.
648 Previous declarations include declarations for base classes unless
649 implementsOnly was used.
651 This function is provided for convenience. It provides a more
652 convenient way to call `classImplements`. For example::
654 @implementer(I1)
655 class C(object):
656 pass
658 is equivalent to calling::
660 classImplements(C, I1)
662 after the class has been created.
664 .. seealso:: `classImplements`
665 The change history provided there applies to this function too.
666 """
667 __slots__ = ('interfaces',)
669 def __init__(self, *interfaces):
670 self.interfaces = interfaces
672 def __call__(self, ob):
673 if isinstance(ob, DescriptorAwareMetaClasses):
674 # This is the common branch for new-style (object) and
675 # on Python 2 old-style classes.
676 classImplements(ob, *self.interfaces)
677 return ob
679 spec_name = _implements_name(ob)
680 spec = Implements.named(spec_name, *self.interfaces)
681 try:
682 ob.__implemented__ = spec
683 except AttributeError:
684 raise TypeError("Can't declare implements", ob)
685 return ob
687class implementer_only(object):
688 """Declare the only interfaces implemented by instances of a class
690 This function is called as a class decorator.
692 The arguments are one or more interfaces or interface
693 specifications (`~zope.interface.interfaces.IDeclaration` objects).
695 Previous declarations including declarations for base classes
696 are overridden.
698 This function is provided for convenience. It provides a more
699 convenient way to call `classImplementsOnly`. For example::
701 @implementer_only(I1)
702 class C(object): pass
704 is equivalent to calling::
706 classImplementsOnly(I1)
708 after the class has been created.
709 """
711 def __init__(self, *interfaces):
712 self.interfaces = interfaces
714 def __call__(self, ob):
715 if isinstance(ob, (FunctionType, MethodType)):
716 # XXX Does this decorator make sense for anything but classes?
717 # I don't think so. There can be no inheritance of interfaces
718 # on a method or function....
719 raise ValueError('The implementer_only decorator is not '
720 'supported for methods or functions.')
722 # Assume it's a class:
723 classImplementsOnly(ob, *self.interfaces)
724 return ob
726def _implements(name, interfaces, do_classImplements):
727 # This entire approach is invalid under Py3K. Don't even try to fix
728 # the coverage for this block there. :(
729 frame = sys._getframe(2) # pylint:disable=protected-access
730 locals = frame.f_locals # pylint:disable=redefined-builtin
732 # Try to make sure we were called from a class def. In 2.2.0 we can't
733 # check for __module__ since it doesn't seem to be added to the locals
734 # until later on.
735 if locals is frame.f_globals or '__module__' not in locals:
736 raise TypeError(name+" can be used only from a class definition.")
738 if '__implements_advice_data__' in locals:
739 raise TypeError(name+" can be used only once in a class definition.")
741 locals['__implements_advice_data__'] = interfaces, do_classImplements
742 addClassAdvisor(_implements_advice, depth=3)
744def implements(*interfaces):
745 """
746 Declare interfaces implemented by instances of a class.
748 .. deprecated:: 5.0
749 This only works for Python 2. The `implementer` decorator
750 is preferred for all versions.
752 This function is called in a class definition.
754 The arguments are one or more interfaces or interface
755 specifications (`~zope.interface.interfaces.IDeclaration`
756 objects).
758 The interfaces given (including the interfaces in the
759 specifications) are added to any interfaces previously declared.
761 Previous declarations include declarations for base classes unless
762 `implementsOnly` was used.
764 This function is provided for convenience. It provides a more
765 convenient way to call `classImplements`. For example::
767 implements(I1)
769 is equivalent to calling::
771 classImplements(C, I1)
773 after the class has been created.
774 """
775 # This entire approach is invalid under Py3K. Don't even try to fix
776 # the coverage for this block there. :(
777 if PYTHON3:
778 raise TypeError(_ADVICE_ERROR % 'implementer')
779 _implements("implements", interfaces, classImplements)
781def implementsOnly(*interfaces):
782 """Declare the only interfaces implemented by instances of a class
784 This function is called in a class definition.
786 The arguments are one or more interfaces or interface
787 specifications (`~zope.interface.interfaces.IDeclaration` objects).
789 Previous declarations including declarations for base classes
790 are overridden.
792 This function is provided for convenience. It provides a more
793 convenient way to call `classImplementsOnly`. For example::
795 implementsOnly(I1)
797 is equivalent to calling::
799 classImplementsOnly(I1)
801 after the class has been created.
802 """
803 # This entire approach is invalid under Py3K. Don't even try to fix
804 # the coverage for this block there. :(
805 if PYTHON3:
806 raise TypeError(_ADVICE_ERROR % 'implementer_only')
807 _implements("implementsOnly", interfaces, classImplementsOnly)
809##############################################################################
810#
811# Instance declarations
813class Provides(Declaration): # Really named ProvidesClass
814 """Implement ``__provides__``, the instance-specific specification
816 When an object is pickled, we pickle the interfaces that it implements.
817 """
819 def __init__(self, cls, *interfaces):
820 self.__args = (cls, ) + interfaces
821 self._cls = cls
822 Declaration.__init__(self, *self._add_interfaces_to_cls(interfaces, cls))
824 # Added to by ``moduleProvides``, et al
825 _v_module_names = ()
827 def __repr__(self):
828 # The typical way to create instances of this
829 # object is via calling ``directlyProvides(...)`` or ``alsoProvides()``,
830 # but that's not the only way. Proxies, for example,
831 # directly use the ``Provides(...)`` function (which is the
832 # more generic method, and what we pickle as). We're after the most
833 # readable, useful repr in the common case, so we use the most
834 # common name.
835 #
836 # We also cooperate with ``moduleProvides`` to attempt to do the
837 # right thing for that API. See it for details.
838 function_name = 'directlyProvides'
839 if self._cls is ModuleType and self._v_module_names:
840 # See notes in ``moduleProvides``/``directlyProvides``
841 providing_on_module = True
842 interfaces = self.__args[1:]
843 else:
844 providing_on_module = False
845 interfaces = (self._cls,) + self.__bases__
846 ordered_names = self._argument_names_for_repr(interfaces)
847 if providing_on_module:
848 mod_names = self._v_module_names
849 if len(mod_names) == 1:
850 mod_names = "sys.modules[%r]" % mod_names[0]
851 ordered_names = (
852 '%s, ' % (mod_names,)
853 ) + ordered_names
854 return "%s(%s)" % (
855 function_name,
856 ordered_names,
857 )
859 def __reduce__(self):
860 # This reduces to the Provides *function*, not
861 # this class.
862 return Provides, self.__args
864 __module__ = 'zope.interface'
866 def __get__(self, inst, cls):
867 """Make sure that a class __provides__ doesn't leak to an instance
868 """
869 if inst is None and cls is self._cls:
870 # We were accessed through a class, so we are the class'
871 # provides spec. Just return this object, but only if we are
872 # being called on the same class that we were defined for:
873 return self
875 raise AttributeError('__provides__')
877ProvidesClass = Provides
879# Registry of instance declarations
880# This is a memory optimization to allow objects to share specifications.
881InstanceDeclarations = weakref.WeakValueDictionary()
883def Provides(*interfaces): # pylint:disable=function-redefined
884 """Cache instance declarations
886 Instance declarations are shared among instances that have the same
887 declaration. The declarations are cached in a weak value dictionary.
888 """
889 spec = InstanceDeclarations.get(interfaces)
890 if spec is None:
891 spec = ProvidesClass(*interfaces)
892 InstanceDeclarations[interfaces] = spec
894 return spec
896Provides.__safe_for_unpickling__ = True
899def directlyProvides(object, *interfaces): # pylint:disable=redefined-builtin
900 """Declare interfaces declared directly for an object
902 The arguments after the object are one or more interfaces or interface
903 specifications (`~zope.interface.interfaces.IDeclaration` objects).
905 The interfaces given (including the interfaces in the specifications)
906 replace interfaces previously declared for the object.
907 """
908 cls = getattr(object, '__class__', None)
909 if cls is not None and getattr(cls, '__class__', None) is cls:
910 # It's a meta class (well, at least it it could be an extension class)
911 # Note that we can't get here from Py3k tests: there is no normal
912 # class which isn't descriptor aware.
913 if not isinstance(object,
914 DescriptorAwareMetaClasses):
915 raise TypeError("Attempt to make an interface declaration on a "
916 "non-descriptor-aware class")
918 interfaces = _normalizeargs(interfaces)
919 if cls is None:
920 cls = type(object)
922 issub = False
923 for damc in DescriptorAwareMetaClasses:
924 if issubclass(cls, damc):
925 issub = True
926 break
927 if issub:
928 # we have a class or type. We'll use a special descriptor
929 # that provides some extra caching
930 object.__provides__ = ClassProvides(object, cls, *interfaces)
931 else:
932 provides = object.__provides__ = Provides(cls, *interfaces)
933 # See notes in ``moduleProvides``.
934 if issubclass(cls, ModuleType) and hasattr(object, '__name__'):
935 provides._v_module_names += (object.__name__,)
939def alsoProvides(object, *interfaces): # pylint:disable=redefined-builtin
940 """Declare interfaces declared directly for an object
942 The arguments after the object are one or more interfaces or interface
943 specifications (`~zope.interface.interfaces.IDeclaration` objects).
945 The interfaces given (including the interfaces in the specifications) are
946 added to the interfaces previously declared for the object.
947 """
948 directlyProvides(object, directlyProvidedBy(object), *interfaces)
951def noLongerProvides(object, interface): # pylint:disable=redefined-builtin
952 """ Removes a directly provided interface from an object.
953 """
954 directlyProvides(object, directlyProvidedBy(object) - interface)
955 if interface.providedBy(object):
956 raise ValueError("Can only remove directly provided interfaces.")
959@_use_c_impl
960class ClassProvidesBase(SpecificationBase):
962 __slots__ = (
963 '_cls',
964 '_implements',
965 )
967 def __get__(self, inst, cls):
968 # member slots are set by subclass
969 # pylint:disable=no-member
970 if cls is self._cls:
971 # We only work if called on the class we were defined for
973 if inst is None:
974 # We were accessed through a class, so we are the class'
975 # provides spec. Just return this object as is:
976 return self
978 return self._implements
980 raise AttributeError('__provides__')
983class ClassProvides(Declaration, ClassProvidesBase):
984 """Special descriptor for class ``__provides__``
986 The descriptor caches the implementedBy info, so that
987 we can get declarations for objects without instance-specific
988 interfaces a bit quicker.
989 """
991 __slots__ = (
992 '__args',
993 )
995 def __init__(self, cls, metacls, *interfaces):
996 self._cls = cls
997 self._implements = implementedBy(cls)
998 self.__args = (cls, metacls, ) + interfaces
999 Declaration.__init__(self, *self._add_interfaces_to_cls(interfaces, metacls))
1001 def __repr__(self):
1002 # There are two common ways to get instances of this object:
1003 # The most interesting way is calling ``@provider(..)`` as a decorator
1004 # of a class; this is the same as calling ``directlyProvides(cls, ...)``.
1005 #
1006 # The other way is by default: anything that invokes ``implementedBy(x)``
1007 # will wind up putting an instance in ``type(x).__provides__``; this includes
1008 # the ``@implementer(...)`` decorator. Those instances won't have any
1009 # interfaces.
1010 #
1011 # Thus, as our repr, we go with the ``directlyProvides()`` syntax.
1012 interfaces = (self._cls, ) + self.__args[2:]
1013 ordered_names = self._argument_names_for_repr(interfaces)
1014 return "directlyProvides(%s)" % (ordered_names,)
1016 def __reduce__(self):
1017 return self.__class__, self.__args
1019 # Copy base-class method for speed
1020 __get__ = ClassProvidesBase.__get__
1023def directlyProvidedBy(object): # pylint:disable=redefined-builtin
1024 """Return the interfaces directly provided by the given object
1026 The value returned is an `~zope.interface.interfaces.IDeclaration`.
1027 """
1028 provides = getattr(object, "__provides__", None)
1029 if (
1030 provides is None # no spec
1031 # We might have gotten the implements spec, as an
1032 # optimization. If so, it's like having only one base, that we
1033 # lop off to exclude class-supplied declarations:
1034 or isinstance(provides, Implements)
1035 ):
1036 return _empty
1038 # Strip off the class part of the spec:
1039 return Declaration(provides.__bases__[:-1])
1042def classProvides(*interfaces):
1043 """Declare interfaces provided directly by a class
1045 This function is called in a class definition.
1047 The arguments are one or more interfaces or interface specifications
1048 (`~zope.interface.interfaces.IDeclaration` objects).
1050 The given interfaces (including the interfaces in the specifications)
1051 are used to create the class's direct-object interface specification.
1052 An error will be raised if the module class has an direct interface
1053 specification. In other words, it is an error to call this function more
1054 than once in a class definition.
1056 Note that the given interfaces have nothing to do with the interfaces
1057 implemented by instances of the class.
1059 This function is provided for convenience. It provides a more convenient
1060 way to call `directlyProvides` for a class. For example::
1062 classProvides(I1)
1064 is equivalent to calling::
1066 directlyProvides(theclass, I1)
1068 after the class has been created.
1069 """
1070 # This entire approach is invalid under Py3K. Don't even try to fix
1071 # the coverage for this block there. :(
1073 if PYTHON3:
1074 raise TypeError(_ADVICE_ERROR % 'provider')
1076 frame = sys._getframe(1) # pylint:disable=protected-access
1077 locals = frame.f_locals # pylint:disable=redefined-builtin
1079 # Try to make sure we were called from a class def
1080 if (locals is frame.f_globals) or ('__module__' not in locals):
1081 raise TypeError("classProvides can be used only from a "
1082 "class definition.")
1084 if '__provides__' in locals:
1085 raise TypeError(
1086 "classProvides can only be used once in a class definition.")
1088 locals["__provides__"] = _normalizeargs(interfaces)
1090 addClassAdvisor(_classProvides_advice, depth=2)
1092def _classProvides_advice(cls):
1093 # This entire approach is invalid under Py3K. Don't even try to fix
1094 # the coverage for this block there. :(
1095 interfaces = cls.__dict__['__provides__']
1096 del cls.__provides__
1097 directlyProvides(cls, *interfaces)
1098 return cls
1101class provider(object):
1102 """Class decorator version of classProvides"""
1104 def __init__(self, *interfaces):
1105 self.interfaces = interfaces
1107 def __call__(self, ob):
1108 directlyProvides(ob, *self.interfaces)
1109 return ob
1112def moduleProvides(*interfaces):
1113 """Declare interfaces provided by a module
1115 This function is used in a module definition.
1117 The arguments are one or more interfaces or interface specifications
1118 (`~zope.interface.interfaces.IDeclaration` objects).
1120 The given interfaces (including the interfaces in the specifications) are
1121 used to create the module's direct-object interface specification. An
1122 error will be raised if the module already has an interface specification.
1123 In other words, it is an error to call this function more than once in a
1124 module definition.
1126 This function is provided for convenience. It provides a more convenient
1127 way to call directlyProvides. For example::
1129 moduleProvides(I1)
1131 is equivalent to::
1133 directlyProvides(sys.modules[__name__], I1)
1134 """
1135 frame = sys._getframe(1) # pylint:disable=protected-access
1136 locals = frame.f_locals # pylint:disable=redefined-builtin
1138 # Try to make sure we were called from a module body
1139 if (locals is not frame.f_globals) or ('__name__' not in locals):
1140 raise TypeError(
1141 "moduleProvides can only be used from a module definition.")
1143 if '__provides__' in locals:
1144 raise TypeError(
1145 "moduleProvides can only be used once in a module definition.")
1147 # Note: This is cached based on the key ``(ModuleType, *interfaces)``;
1148 # One consequence is that any module that provides the same interfaces
1149 # gets the same ``__repr__``, meaning that you can't tell what module
1150 # such a declaration came from. Adding the module name to ``_v_module_names``
1151 # attempts to correct for this; it works in some common situations, but fails
1152 # (1) after pickling (the data is lost) and (2) if declarations are
1153 # actually shared and (3) if the alternate spelling of ``directlyProvides()``
1154 # is used. Problem (3) is fixed by cooperating with ``directlyProvides``
1155 # to maintain this information, and problem (2) is worked around by
1156 # printing all the names, but (1) is unsolvable without introducing
1157 # new classes or changing the stored data...but it doesn't actually matter,
1158 # because ``ModuleType`` can't be pickled!
1159 p = locals["__provides__"] = Provides(ModuleType,
1160 *_normalizeargs(interfaces))
1161 p._v_module_names += (locals['__name__'],)
1164##############################################################################
1165#
1166# Declaration querying support
1168# XXX: is this a fossil? Nobody calls it, no unit tests exercise it, no
1169# doctests import it, and the package __init__ doesn't import it.
1170# (Answer: Versions of zope.container prior to 4.4.0 called this,
1171# and zope.proxy.decorator up through at least 4.3.5 called this.)
1172def ObjectSpecification(direct, cls):
1173 """Provide object specifications
1175 These combine information for the object and for it's classes.
1176 """
1177 return Provides(cls, direct) # pragma: no cover fossil
1179@_use_c_impl
1180def getObjectSpecification(ob):
1181 try:
1182 provides = ob.__provides__
1183 except AttributeError:
1184 provides = None
1186 if provides is not None:
1187 if isinstance(provides, SpecificationBase):
1188 return provides
1190 try:
1191 cls = ob.__class__
1192 except AttributeError:
1193 # We can't get the class, so just consider provides
1194 return _empty
1195 return implementedBy(cls)
1198@_use_c_impl
1199def providedBy(ob):
1200 """
1201 Return the interfaces provided by *ob*.
1203 If *ob* is a :class:`super` object, then only interfaces implemented
1204 by the remainder of the classes in the method resolution order are
1205 considered. Interfaces directly provided by the object underlying *ob*
1206 are not.
1207 """
1208 # Here we have either a special object, an old-style declaration
1209 # or a descriptor
1211 # Try to get __providedBy__
1212 try:
1213 if isinstance(ob, super): # Some objects raise errors on isinstance()
1214 return implementedBy(ob)
1216 r = ob.__providedBy__
1217 except AttributeError:
1218 # Not set yet. Fall back to lower-level thing that computes it
1219 return getObjectSpecification(ob)
1221 try:
1222 # We might have gotten a descriptor from an instance of a
1223 # class (like an ExtensionClass) that doesn't support
1224 # descriptors. We'll make sure we got one by trying to get
1225 # the only attribute, which all specs have.
1226 r.extends
1227 except AttributeError:
1229 # The object's class doesn't understand descriptors.
1230 # Sigh. We need to get an object descriptor, but we have to be
1231 # careful. We want to use the instance's __provides__, if
1232 # there is one, but only if it didn't come from the class.
1234 try:
1235 r = ob.__provides__
1236 except AttributeError:
1237 # No __provides__, so just fall back to implementedBy
1238 return implementedBy(ob.__class__)
1240 # We need to make sure we got the __provides__ from the
1241 # instance. We'll do this by making sure we don't get the same
1242 # thing from the class:
1244 try:
1245 cp = ob.__class__.__provides__
1246 except AttributeError:
1247 # The ob doesn't have a class or the class has no
1248 # provides, assume we're done:
1249 return r
1251 if r is cp:
1252 # Oops, we got the provides from the class. This means
1253 # the object doesn't have it's own. We should use implementedBy
1254 return implementedBy(ob.__class__)
1256 return r
1259@_use_c_impl
1260class ObjectSpecificationDescriptor(object):
1261 """Implement the ``__providedBy__`` attribute
1263 The ``__providedBy__`` attribute computes the interfaces provided by
1264 an object. If an object has an ``__provides__`` attribute, that is returned.
1265 Otherwise, `implementedBy` the *cls* is returned.
1267 .. versionchanged:: 5.4.0
1268 Both the default (C) implementation and the Python implementation
1269 now let exceptions raised by accessing ``__provides__`` propagate.
1270 Previously, the C version ignored all exceptions.
1271 .. versionchanged:: 5.4.0
1272 The Python implementation now matches the C implementation and lets
1273 a ``__provides__`` of ``None`` override what the class is declared to
1274 implement.
1275 """
1277 def __get__(self, inst, cls):
1278 """Get an object specification for an object
1279 """
1280 if inst is None:
1281 return getObjectSpecification(cls)
1283 try:
1284 return inst.__provides__
1285 except AttributeError:
1286 return implementedBy(cls)
1289##############################################################################
1291def _normalizeargs(sequence, output=None):
1292 """Normalize declaration arguments
1294 Normalization arguments might contain Declarions, tuples, or single
1295 interfaces.
1297 Anything but individial interfaces or implements specs will be expanded.
1298 """
1299 if output is None:
1300 output = []
1302 cls = sequence.__class__
1303 if InterfaceClass in cls.__mro__ or Implements in cls.__mro__:
1304 output.append(sequence)
1305 else:
1306 for v in sequence:
1307 _normalizeargs(v, output)
1309 return output
1311_empty = _ImmutableDeclaration()
1313objectSpecificationDescriptor = ObjectSpecificationDescriptor()