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##############################################################################
#
# Copyright (c) 2003 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.
#
##############################################################################
"""Class advice.
This module was adapted from 'protocols.advice', part of the Python
Enterprise Application Kit (PEAK). Please notify the PEAK authors
(pje@telecommunity.com and tsarna@sarna.org) if bugs are found or
Zope-specific changes are required, so that the PEAK version of this module
can be kept in sync.
PEAK is a Python application framework that interoperates with (but does
not require) Zope 3 and Twisted. It provides tools for manipulating UML
models, object-relational persistence, aspect-oriented programming, and more.
Visit the PEAK home page at http://peak.telecommunity.com for more information.
"""
from types import FunctionType
__all__ = [
'determineMetaclass',
'getFrameInfo',
'isClassAdvisor',
'minimalBases',
]
import sys
def getFrameInfo(frame):
"""Return (kind,module,locals,globals) for a frame
'kind' is one of "exec", "module", "class", "function call", or "unknown".
"""
f_locals = frame.f_locals
f_globals = frame.f_globals
sameNamespace = f_locals is f_globals
hasModule = '__module__' in f_locals
hasName = '__name__' in f_globals
sameName = hasModule and hasName
sameName = sameName and f_globals['__name__'] == f_locals['__module__']
module = hasName and sys.modules.get(f_globals['__name__']) or None
namespaceIsModule = module and module.__dict__ is f_globals
if not namespaceIsModule:
# some kind of funky exec
kind = "exec"
elif sameNamespace and not hasModule:
kind = "module"
elif sameName and not sameNamespace:
kind = "class"
elif not sameNamespace:
kind = "function call"
else: # pragma: no cover
# How can you have f_locals is f_globals, and have '__module__'
# set? # This is probably module-level code, but with a
# '__module__' variable.
kind = "unknown"
return kind, module, f_locals, f_globals
def isClassAdvisor(ob):
"""True if 'ob' is a class advisor function"""
return isinstance(ob, FunctionType) and hasattr(ob, 'previousMetaclass')
def determineMetaclass(bases, explicit_mc=None):
"""Determine metaclass from 1+ bases and optional explicit __metaclass__"""
meta = [getattr(b, '__class__', type(b)) for b in bases]
if explicit_mc is not None:
# The explicit metaclass needs to be verified for compatibility
# as well, and allowed to resolve the incompatible bases, if any
meta.append(explicit_mc)
if len(meta) == 1:
# easy case
return meta[0]
candidates = minimalBases(meta) # minimal set of metaclasses
if len(candidates) > 1:
# We could auto-combine, but for now we won't...
raise TypeError("Incompatible metatypes", bases)
# Just one, return it
return candidates[0]
def minimalBases(classes):
"""Reduce a list of base classes to its ordered minimum equivalent"""
candidates = []
for m in classes:
for n in classes:
if issubclass(n, m) and m is not n:
break
else:
# m has no subclasses in 'classes'
if m in candidates:
candidates.remove(m) # ensure that we're later in the list
candidates.append(m)
return candidates
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