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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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