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#!/usr/bin/env python
# -*- coding: utf8 -*-
# :Id: $Id$
# :Copyright: © 2011 Günter Milde.
# :License: Released under the terms of the `2-Clause BSD license`_, in short:
#
# Copying and distribution of this file, with or without modification,
# are permitted in any medium without royalty provided the copyright
# notice and this notice are preserved.
# This file is offered as-is, without any warranty.
#
# .. _2-Clause BSD license: http://www.spdx.org/licenses/BSD-2-Clause
"""
Error reporting should be safe from encoding/decoding errors.
However, implicit conversions of strings and exceptions like
>>> u'%s world: %s' % ('H\xe4llo', Exception(u'H\xe4llo')
fail in some Python versions:
* In Python <= 2.6, ``unicode(<exception instance>)`` uses
`__str__` and fails with non-ASCII chars in`unicode` arguments.
(work around http://bugs.python.org/issue2517):
* In Python 2, unicode(<exception instance>) fails, with non-ASCII
chars in arguments. (Use case: in some locales, the errstr
argument of IOError contains non-ASCII chars.)
* In Python 2, str(<exception instance>) fails, with non-ASCII chars
in `unicode` arguments.
The `SafeString`, `ErrorString` and `ErrorOutput` classes handle
common exceptions.
"""
import sys, codecs
# Guess the locale's encoding.
# If no valid guess can be made, locale_encoding is set to `None`:
try:
import locale # module missing in Jython
except ImportError:
locale_encoding = None
else:
locale_encoding = locale.getlocale()[1] or locale.getdefaultlocale()[1]
# locale.getpreferredencoding([do_setlocale=True|False])
# has side-effects | might return a wrong guess.
# (cf. Update 1 in http://stackoverflow.com/questions/4082645/using-python-2-xs-locale-module-to-format-numbers-and-currency)
try:
codecs.lookup(locale_encoding or '') # None -> ''
except LookupError:
locale_encoding = None
class SafeString(object):
"""
A wrapper providing robust conversion to `str` and `unicode`.
"""
def __init__(self, data, encoding=None, encoding_errors='backslashreplace',
decoding_errors='replace'):
self.data = data
self.encoding = (encoding or getattr(data, 'encoding', None) or
locale_encoding or 'ascii')
self.encoding_errors = encoding_errors
self.decoding_errors = decoding_errors
def __str__(self):
try:
return str(self.data)
except UnicodeEncodeError, err:
if isinstance(self.data, Exception):
args = [str(SafeString(arg, self.encoding,
self.encoding_errors))
for arg in self.data.args]
return ', '.join(args)
if isinstance(self.data, unicode):
if sys.version_info > (3,0):
return self.data
else:
return self.data.encode(self.encoding,
self.encoding_errors)
raise
def __unicode__(self):
"""
Return unicode representation of `self.data`.
Try ``unicode(self.data)``, catch `UnicodeError` and
* if `self.data` is an Exception instance, work around
http://bugs.python.org/issue2517 with an emulation of
Exception.__unicode__,
* else decode with `self.encoding` and `self.decoding_errors`.
"""
try:
u = unicode(self.data)
if isinstance(self.data, EnvironmentError):
u = u.replace(": u'", ": '") # normalize filename quoting
return u
except UnicodeError, error: # catch ..Encode.. and ..Decode.. errors
if isinstance(self.data, EnvironmentError):
return u"[Errno %s] %s: '%s'" % (self.data.errno,
SafeString(self.data.strerror, self.encoding,
self.decoding_errors),
SafeString(self.data.filename, self.encoding,
self.decoding_errors))
if isinstance(self.data, Exception):
args = [unicode(SafeString(arg, self.encoding,
decoding_errors=self.decoding_errors))
for arg in self.data.args]
return u', '.join(args)
if isinstance(error, UnicodeDecodeError):
return unicode(self.data, self.encoding, self.decoding_errors)
raise
class ErrorString(SafeString):
"""
Safely report exception type and message.
"""
def __str__(self):
return '%s: %s' % (self.data.__class__.__name__,
super(ErrorString, self).__str__())
def __unicode__(self):
return u'%s: %s' % (self.data.__class__.__name__,
super(ErrorString, self).__unicode__())
class ErrorOutput(object):
"""
Wrapper class for file-like error streams with
failsave de- and encoding of `str`, `bytes`, `unicode` and
`Exception` instances.
"""
def __init__(self, stream=None, encoding=None,
encoding_errors='backslashreplace',
decoding_errors='replace'):
"""
:Parameters:
- `stream`: a file-like object,
a string (path to a file),
`None` (write to `sys.stderr`, default), or
evaluating to `False` (write() requests are ignored).
- `encoding`: `stream` text encoding. Guessed if None.
- `encoding_errors`: how to treat encoding errors.
"""
if stream is None:
stream = sys.stderr
elif not(stream):
stream = False
# if `stream` is a file name, open it
elif isinstance(stream, str):
stream = open(stream, 'w')
elif isinstance(stream, unicode):
stream = open(stream.encode(sys.getfilesystemencoding()), 'w')
self.stream = stream
"""Where warning output is sent."""
self.encoding = (encoding or getattr(stream, 'encoding', None) or
locale_encoding or 'ascii')
"""The output character encoding."""
self.encoding_errors = encoding_errors
"""Encoding error handler."""
self.decoding_errors = decoding_errors
"""Decoding error handler."""
def write(self, data):
"""
Write `data` to self.stream. Ignore, if self.stream is False.
`data` can be a `string`, `unicode`, or `Exception` instance.
"""
if self.stream is False:
return
if isinstance(data, Exception):
data = unicode(SafeString(data, self.encoding,
self.encoding_errors, self.decoding_errors))
try:
self.stream.write(data)
except UnicodeEncodeError:
self.stream.write(data.encode(self.encoding, self.encoding_errors))
except TypeError: # in Python 3, stderr expects unicode
if self.stream in (sys.stderr, sys.stdout):
self.stream.buffer.write(data) # write bytes to raw stream
else:
self.stream.write(unicode(data, self.encoding,
self.decoding_errors))
def close(self):
"""
Close the error-output stream.
Ignored if the stream is` sys.stderr` or `sys.stdout` or has no
close() method.
"""
if self.stream in (sys.stdout, sys.stderr):
return
try:
self.stream.close()
except AttributeError:
pass
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