Current File : //lib/python3/dist-packages/zope/interface/verify.py
##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Verify interface implementations
"""
from __future__ import print_function
import inspect
import sys
from types import FunctionType
from types import MethodType
from zope.interface._compat import PYPY2
from zope.interface.exceptions import BrokenImplementation
from zope.interface.exceptions import BrokenMethodImplementation
from zope.interface.exceptions import DoesNotImplement
from zope.interface.exceptions import Invalid
from zope.interface.exceptions import MultipleInvalid
from zope.interface.interface import fromMethod, fromFunction, Method
__all__ = [
'verifyObject',
'verifyClass',
]
# This will be monkey-patched when running under Zope 2, so leave this
# here:
MethodTypes = (MethodType, )
def _verify(iface, candidate, tentative=False, vtype=None):
"""
Verify that *candidate* might correctly provide *iface*.
This involves:
- Making sure the candidate claims that it provides the
interface using ``iface.providedBy`` (unless *tentative* is `True`,
in which case this step is skipped). This means that the candidate's class
declares that it `implements <zope.interface.implementer>` the interface,
or the candidate itself declares that it `provides <zope.interface.provider>`
the interface
- Making sure the candidate defines all the necessary methods
- Making sure the methods have the correct signature (to the
extent possible)
- Making sure the candidate defines all the necessary attributes
:return bool: Returns a true value if everything that could be
checked passed.
:raises zope.interface.Invalid: If any of the previous
conditions does not hold.
.. versionchanged:: 5.0
If multiple methods or attributes are invalid, all such errors
are collected and reported. Previously, only the first error was reported.
As a special case, if only one such error is present, it is raised
alone, like before.
"""
if vtype == 'c':
tester = iface.implementedBy
else:
tester = iface.providedBy
excs = []
if not tentative and not tester(candidate):
excs.append(DoesNotImplement(iface, candidate))
for name, desc in iface.namesAndDescriptions(all=True):
try:
_verify_element(iface, name, desc, candidate, vtype)
except Invalid as e:
excs.append(e)
if excs:
if len(excs) == 1:
raise excs[0]
raise MultipleInvalid(iface, candidate, excs)
return True
def _verify_element(iface, name, desc, candidate, vtype):
# Here the `desc` is either an `Attribute` or `Method` instance
try:
attr = getattr(candidate, name)
except AttributeError:
if (not isinstance(desc, Method)) and vtype == 'c':
# We can't verify non-methods on classes, since the
# class may provide attrs in it's __init__.
return
# TODO: On Python 3, this should use ``raise...from``
raise BrokenImplementation(iface, desc, candidate)
if not isinstance(desc, Method):
# If it's not a method, there's nothing else we can test
return
if inspect.ismethoddescriptor(attr) or inspect.isbuiltin(attr):
# The first case is what you get for things like ``dict.pop``
# on CPython (e.g., ``verifyClass(IFullMapping, dict))``). The
# second case is what you get for things like ``dict().pop`` on
# CPython (e.g., ``verifyObject(IFullMapping, dict()))``.
# In neither case can we get a signature, so there's nothing
# to verify. Even the inspect module gives up and raises
# ValueError: no signature found. The ``__text_signature__`` attribute
# isn't typically populated either.
#
# Note that on PyPy 2 or 3 (up through 7.3 at least), these are
# not true for things like ``dict.pop`` (but might be true for C extensions?)
return
if isinstance(attr, FunctionType):
if sys.version_info[0] >= 3 and isinstance(candidate, type) and vtype == 'c':
# This is an "unbound method" in Python 3.
# Only unwrap this if we're verifying implementedBy;
# otherwise we can unwrap @staticmethod on classes that directly
# provide an interface.
meth = fromFunction(attr, iface, name=name,
imlevel=1)
else:
# Nope, just a normal function
meth = fromFunction(attr, iface, name=name)
elif (isinstance(attr, MethodTypes)
and type(attr.__func__) is FunctionType):
meth = fromMethod(attr, iface, name)
elif isinstance(attr, property) and vtype == 'c':
# Without an instance we cannot be sure it's not a
# callable.
# TODO: This should probably check inspect.isdatadescriptor(),
# a more general form than ``property``
return
else:
if not callable(attr):
raise BrokenMethodImplementation(desc, "implementation is not a method",
attr, iface, candidate)
# sigh, it's callable, but we don't know how to introspect it, so
# we have to give it a pass.
return
# Make sure that the required and implemented method signatures are
# the same.
mess = _incompat(desc.getSignatureInfo(), meth.getSignatureInfo())
if mess:
if PYPY2 and _pypy2_false_positive(mess, candidate, vtype):
return
raise BrokenMethodImplementation(desc, mess, attr, iface, candidate)
def verifyClass(iface, candidate, tentative=False):
"""
Verify that the *candidate* might correctly provide *iface*.
"""
return _verify(iface, candidate, tentative, vtype='c')
def verifyObject(iface, candidate, tentative=False):
return _verify(iface, candidate, tentative, vtype='o')
verifyObject.__doc__ = _verify.__doc__
_MSG_TOO_MANY = 'implementation requires too many arguments'
_KNOWN_PYPY2_FALSE_POSITIVES = frozenset((
_MSG_TOO_MANY,
))
def _pypy2_false_positive(msg, candidate, vtype):
# On PyPy2, builtin methods and functions like
# ``dict.pop`` that take pseudo-optional arguments
# (those with no default, something you can't express in Python 2
# syntax; CPython uses special internal APIs to implement these methods)
# return false failures because PyPy2 doesn't expose any way
# to detect this pseudo-optional status. PyPy3 doesn't have this problem
# because of __defaults_count__, and CPython never gets here because it
# returns true for ``ismethoddescriptor`` or ``isbuiltin``.
#
# We can't catch all such cases, but we can handle the common ones.
#
if msg not in _KNOWN_PYPY2_FALSE_POSITIVES:
return False
known_builtin_types = vars(__builtins__).values()
candidate_type = candidate if vtype == 'c' else type(candidate)
if candidate_type in known_builtin_types:
return True
return False
def _incompat(required, implemented):
#if (required['positional'] !=
# implemented['positional'][:len(required['positional'])]
# and implemented['kwargs'] is None):
# return 'imlementation has different argument names'
if len(implemented['required']) > len(required['required']):
return _MSG_TOO_MANY
if ((len(implemented['positional']) < len(required['positional']))
and not implemented['varargs']):
return "implementation doesn't allow enough arguments"
if required['kwargs'] and not implemented['kwargs']:
return "implementation doesn't support keyword arguments"
if required['varargs'] and not implemented['varargs']:
return "implementation doesn't support variable arguments"
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