##############################################################################
#
# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (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
#
##############################################################################
from types import StringType,UnicodeType,InstanceType
nasty_exception_str = Exception.__str__.im_func
def ustr(v):
"""Convert any object to a plain string or unicode string,
minimising the chance of raising a UnicodeError. This
even works with uncooperative objects like Exceptions
"""
string_types = (StringType,UnicodeType)
if type(v) in string_types:
return v
else:
fn = getattr(v,'__str__',None)
if fn is not None:
# An object that wants to present its own string representation,
# but we dont know what type of string. We cant use any built-in
# function like str() or unicode() to retrieve it because
# they all constrain the type which potentially raises an exception.
# To avoid exceptions we have to call __str__ direct.
if getattr(fn,'im_func',None)==nasty_exception_str:
# Exception objects have been optimised into C, and their
# __str__ function fails when given a unicode object.
# Unfortunately this scenario is all too common when
# migrating to unicode, because of code which does:
# raise ValueError(something_I_wasnt_expecting_to_be_unicode)
return _exception_str(v)
else:
# Trust the object to do this right
v = fn()
if type(v) in string_types:
return v
else:
raise ValueError('__str__ returned wrong type')
# Drop through for non-instance types, and instances that
# do not define a special __str__
return str(v)
def _exception_str(exc):
if hasattr(exc, 'args'):
if not exc.args:
return ''
elif len(exc.args) == 1:
return ustr(exc.args[0])
else:
return str(exc.args)
return str(exc)
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