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From: Jordan Moldow <jmoldow@box.com>
Date: Wed, 23 Mar 2016 01:42:37 -0700
Subject: [PATCH] Prevent crashing from UnicodeDecodeError
On Python 2, `sys.stdout` and `print` can normally handle any
combination of `str` and `unicode` objects. However,
`StringIO.StringIO` can only safely handle one or the other. If
the program writes both a `unicode` string, and a non-ASCII
`str` string, then the `getvalue()` method will fail with
`UnicodeDecodeError` [1].
In nose, that causes the script to suddenly abort, with the
cryptic `UnicodeDecodeError`.
This fix catches `UnicodeError` when trying to get the captured
output, and will replace the captured output with a warning
message.
Fixes #816
[1] <https://github.com/python/cpython/blob/2.7/Lib/StringIO.py#L258>
Patch-Source: https://github.com/nose-devs/nose/pull/988
diff --git a/nose/plugins/capture.py b/nose/plugins/capture.py
index c81f21ec..e7bbdd55 100644
--- a/nose/plugins/capture.py
+++ b/nose/plugins/capture.py
@@ -12,6 +12,7 @@
import logging
import os
import sys
+import traceback
from nose.plugins.base import Plugin
from nose.pyversion import exc_to_unicode, force_unicode
from nose.util import ln
@@ -71,26 +72,56 @@ def beforeTest(self, test):
def formatError(self, test, err):
"""Add captured output to error report.
"""
- test.capturedOutput = output = self.buffer
+ test.capturedOutput = output = ''
+ output_exc_info = None
+ try:
+ test.capturedOutput = output = self.buffer
+ except UnicodeError:
+ # python2's StringIO.StringIO [1] class has this warning:
+ #
+ # The StringIO object can accept either Unicode or 8-bit strings,
+ # but mixing the two may take some care. If both are used, 8-bit
+ # strings that cannot be interpreted as 7-bit ASCII (that use the
+ # 8th bit) will cause a UnicodeError to be raised when getvalue()
+ # is called.
+ #
+ # This exception handler is a protection against issue #816 [2].
+ # Capturing the exception info allows us to display it back to the
+ # user.
+ #
+ # [1] <https://github.com/python/cpython/blob/2.7/Lib/StringIO.py#L258>
+ # [2] <https://github.com/nose-devs/nose/issues/816>
+ output_exc_info = sys.exc_info()
self._buf = None
- if not output:
+ if (not output) and (not output_exc_info):
# Don't return None as that will prevent other
# formatters from formatting and remove earlier formatters
# formats, instead return the err we got
return err
ec, ev, tb = err
- return (ec, self.addCaptureToErr(ev, output), tb)
+ return (ec, self.addCaptureToErr(ev, output, output_exc_info=output_exc_info), tb)
def formatFailure(self, test, err):
"""Add captured output to failure report.
"""
return self.formatError(test, err)
- def addCaptureToErr(self, ev, output):
+ def addCaptureToErr(self, ev, output, output_exc_info=None):
+ # If given, output_exc_info should be a 3-tuple from sys.exc_info(),
+ # from an exception raised while trying to get the captured output.
ev = exc_to_unicode(ev)
output = force_unicode(output)
- return u'\n'.join([ev, ln(u'>> begin captured stdout <<'),
- output, ln(u'>> end captured stdout <<')])
+ error_text = [ev, ln(u'>> begin captured stdout <<'),
+ output, ln(u'>> end captured stdout <<')]
+ if output_exc_info:
+ error_text.extend([u'OUTPUT ERROR: Could not get captured output.',
+ # <https://github.com/python/cpython/blob/2.7/Lib/StringIO.py#L258>
+ # <https://github.com/nose-devs/nose/issues/816>
+ u"The test might've printed both 'unicode' strings and non-ASCII 8-bit 'str' strings.",
+ ln(u'>> begin captured stdout exception traceback <<'),
+ u''.join(traceback.format_exception(*output_exc_info)),
+ ln(u'>> end captured stdout exception traceback <<')])
+ return u'\n'.join(error_text)
def start(self):
self.stdout.append(sys.stdout)
diff --git a/unit_tests/test_capture_plugin.py b/unit_tests/test_capture_plugin.py
index edab7de0..90125d3e 100644
--- a/unit_tests/test_capture_plugin.py
+++ b/unit_tests/test_capture_plugin.py
@@ -4,6 +4,12 @@
from optparse import OptionParser
from nose.config import Config
from nose.plugins.capture import Capture
+from nose.pyversion import force_unicode
+
+if sys.version_info[0] == 2:
+ py2 = True
+else:
+ py2 = False
class TestCapturePlugin(unittest.TestCase):
@@ -62,6 +68,35 @@ def test_captures_nonascii_stdout(self):
c.end()
self.assertEqual(c.buffer, "test 日本\n")
+ def test_does_not_crash_with_mixed_unicode_and_nonascii_str(self):
+ class Dummy:
+ pass
+ d = Dummy()
+ c = Capture()
+ c.start()
+ printed_nonascii_str = force_unicode("test 日本").encode('utf-8')
+ printed_unicode = force_unicode("Hello")
+ print printed_nonascii_str
+ print printed_unicode
+ try:
+ raise Exception("boom")
+ except:
+ err = sys.exc_info()
+ formatted = c.formatError(d, err)
+ _, fev, _ = formatted
+
+ if py2:
+ for string in [force_unicode(printed_nonascii_str, encoding='utf-8'), printed_unicode]:
+ assert string not in fev, "Output unexpectedly found in error message"
+ assert d.capturedOutput == '', "capturedOutput unexpectedly non-empty"
+ assert "OUTPUT ERROR" in fev
+ assert "captured stdout exception traceback" in fev
+ assert "UnicodeDecodeError" in fev
+ else:
+ for string in [repr(printed_nonascii_str), printed_unicode]:
+ assert string in fev, "Output not found in error message"
+ assert string in d.capturedOutput, "Output not attached to test"
+
def test_format_error(self):
class Dummy:
pass
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