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Edit File: 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"