unittest: use ascii() instead of repr() to display values on error

[vstinner]

BPO	10161
Nosy	@vstinner, @voidspace
Files	unittest_ascii.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2010-10-24.21:05:33.001>
created_at = <Date 2010-10-21.00:14:03.526>
labels = ['library', 'expert-unicode']
title = 'unittest: use ascii() instead of repr() to display values on error'
updated_at = <Date 2010-10-25.01:11:34.284>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2010-10-25.01:11:34.284>
actor = 'michael.foord'
assignee = 'none'
closed = True
closed_date = <Date 2010-10-24.21:05:33.001>
closer = 'vstinner'
components = ['Library (Lib)', 'Unicode']
creation = <Date 2010-10-21.00:14:03.526>
creator = 'vstinner'
dependencies = []
files = ['19311']
hgrepos = []
issue_num = 10161
keywords = ['patch']
message_count = 3.0
messages = ['119248', '119531', '119532']
nosy_count = 2.0
nosy_names = ['vstinner', 'michael.foord']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue10161'
versions = ['Python 3.2']

[vstinner]

On a failure, unittest does its best to display values. But sometimes, the output doesn't help me. Example:

FAIL: test_listdir (test.test_pep277.UnicodeFileTests)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/Users/db3l/buildarea/3.x.bolen-tiger/build/Lib/test/test_pep277.py", line 157, in test_listdir
    self.assertEqual(sf0, sf2)
AssertionError: Items in the first set but not the second:
'@test_18608_tmp/ ̈�Υ�Ϋ'
'@test_18608_tmp/ẛ῁῍᾿�῏῝῾�῟῭'
Items in the second set but not the first:
'@test_18608_tmp/ ̈�ΥΥ�̈'
'@test_18608_tmp/ẛ῁῍᾿�᾿῾῾῾῁̀�͂̀'
'@test_18608_tmp/¨�ϒϒ�̈'

This is a test on unicode filenames. I would prefer to see non-ASCII characters as \xHH or \uXXXX than strange characters or boxes.

Do you think that it is a good idea to replace calls to repr() by ascii() in the unittest library?

In Python2, repr(unicode) escapes all non-ASCII characters. But in Python3, only control characters and surrogates are escaped. So the output depends on the terminal encoding.

Write non-ASCII characters in a backtrace may also raise a new error if the terminal is unable to a character. Raise an error while printing an error is just horrible :-)

--

Attached patch is a try to replace repr() by ascii() in the unittest module. But I don't know this library, so don't trust the patch :-)

[vstinner]

Closed with r85829: patch test_pep277 instead of unittest.

[voidspace]

Although this is still a real issue for other users of unittest. If I get time to think about it properly I may reopen.