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Title: 80 failures if COLUMNS env var set to a value other than 80
Type: behavior Stage: patch review
Components: Tests Versions: Python 3.2
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: bethard Nosy List: benjamin.peterson, bethard, brian.curtin, denversc, eric.araujo, eric.smith, janssen, pitrou, r.david.murray
Priority: normal Keywords: patch

Created on 2010-08-10 02:03 by denversc, last changed 2022-04-11 14:57 by admin. This issue is now closed.

File name Uploaded Description Edit denversc, 2010-08-10 02:56 Suggested Patch review denversc, 2010-08-11 03:18 Suggested Patch (update #1) review denversc, 2010-08-11 23:32 Suggested Patch (update #2) review
Messages (11)
msg113504 - (view) Author: Denver Coneybeare (denversc) * Date: 2010-08-10 02:03
If the COLUMNS environment variable is set to a value other than 80 then yields 80 failures.  The value of the COLUMNS environment variable affects line wrapping of the help output and the test cases assume line wraps at 80 columns.  So setting COLUMNS=160, for example, then running the tests will reproduce the failures.  The fix is to invoke: os.environ["COLUMNS"] = "80".

A proposed patch for py3k/Lib/test/ is attached (
msg113506 - (view) Author: Brian Curtin (brian.curtin) * (Python committer) Date: 2010-08-10 02:56
Shouldn't the tests calculate line wrapping based on what is set, rather than brute forcing it to be 80?
msg113515 - (view) Author: Steven Bethard (bethard) * (Python committer) Date: 2010-08-10 09:44
The best solution would be to make sure that a few different column widths are tested. However, in the meantime, the tests do assume 80 columns, so I think it's correct to specify that using os.environ as suggested.

One problem with the proposed patch is that it makes the change globally, and we should be restoring the original setting after the end of the argparse tests.
msg113526 - (view) Author: R. David Murray (r.david.murray) * (Python committer) Date: 2010-08-10 11:53
There's a handy utility for this in EnvironmentVarGuard.
msg113564 - (view) Author: Eric V. Smith (eric.smith) * (Python committer) Date: 2010-08-10 22:17
I agree with Steven: for the current tests we should specify (and restore) 80 columns. We might want to add additional tests at different column widths.
msg113583 - (view) Author: Denver Coneybeare (denversc) * Date: 2010-08-11 03:18
That is a very good point, bethard, that setting os.environ["COLUMNS"] in my suggested patch ( is global and should be test-local.  I've attached an updated patch ( which uses setUp() and tearDown() to prepare and restore the COLUMNS environment variable.  The one difference from my previous patch is that instead of setting the COLUMNS environment variable to 80 I just unset it.

I also considered EnvironmentVarGuard, as suggested by r.david.murray, but I'm not sure it's designed for global setting of environment variables.  EnvironmentVarGuard appears to have been designed to be used as a context manager for an individual test, but the COLUMNS environment variable needs to be adjusted for *every* test.
msg113600 - (view) Author: R. David Murray (r.david.murray) * (Python committer) Date: 2010-08-11 15:06
Your code is fine (though to my tastes a bit verbose...if it were me I'd just put the code in the setUp and tearDown methods and hardcode 'COLUMNS' (it isn't like the name COLUMNS is going to change)...but that's just personal style).

The EnviormentVarGuard version would look like this (untested):

   def setUp(self):
       self.guard = EnvironmentVarGuard()
       self.environ = self.guard.__enter__()
       # Current tests expect 80 column terminal width.
       self.environ['COLUMNS'] = 80

   def tearDown(self):
       self.guard.__exit__(None, None, None)

You could of course delete COLUMNS as you did, but I thought setting it to 80 would be more explicit.

Another comment about the patch: by inspection it appears that adding setUp and tearDown to TestCase isn't enough, since subclasses and mixins define those without calling the superclass versions.
msg113642 - (view) Author: Denver Coneybeare (denversc) * Date: 2010-08-11 23:32
Thanks for the input, r.david.murray.  I've updated my patch and attached it to take into consideration your comments:  The updated patch uses EnviormentVarGuard as suggested, except that it slightly tweaks EnviormentVarGuard so the context manager protocol methods don't have to be invoked directly.

It was also pointed out that "adding setUp and tearDown to TestCase isn't enough, since subclasses and mixins define those without calling the superclass versions", which is true.  However, the tests that override setUp() happen to be those that don't depend on the COLUMNS environment variable.
msg113697 - (view) Author: R. David Murray (r.david.murray) * (Python committer) Date: 2010-08-12 18:26
I don't think it is worthwhile to jump through hoops to avoid calling the special methods.  Your patch also creates an unnecessary dependency on the internal implementation of EnvironmentVarGuard (ie: the fact that currently __enter__ happens to return self...this is *not* part of EnvironmentVarGuard's interface contract).
msg119934 - (view) Author: Antoine Pitrou (pitrou) * (Python committer) Date: 2010-10-29 19:54
As noted in issue10235, this is responsible for buildbot failures:
msg120129 - (view) Author: Steven Bethard (bethard) * (Python committer) Date: 2010-11-01 14:22
Fixed with a variant of Denver's last patch in r86080 for 3.X and r86083 for 2.7.
Date User Action Args
2022-04-11 14:57:05adminsetgithub: 53762
2010-11-01 14:22:38bethardsetstatus: open -> closed
assignee: bethard
resolution: fixed
messages: + msg120129
2010-10-29 19:54:03pitrousetnosy: + pitrou, janssen
messages: + msg119934
2010-10-29 19:53:36pitroulinkissue10235 superseder
2010-08-12 18:26:49r.david.murraysetmessages: + msg113697
stage: test needed -> patch review
2010-08-11 23:32:12denverscsetfiles: +

messages: + msg113642
2010-08-11 15:06:12r.david.murraysetmessages: + msg113600
2010-08-11 03:18:23denverscsetfiles: +

messages: + msg113583
2010-08-10 22:17:33eric.smithsetmessages: + msg113564
2010-08-10 22:15:48eric.araujosetnosy: + eric.araujo
2010-08-10 11:53:39r.david.murraysetnosy: + r.david.murray
messages: + msg113526
2010-08-10 09:44:37bethardsetmessages: + msg113515
2010-08-10 02:57:00brian.curtinsetversions: + Python 3.2, - Python 3.3
nosy: + brian.curtin

messages: + msg113506

stage: test needed
2010-08-10 02:56:04denverscsetfiles: +
2010-08-10 02:55:52denverscsetfiles: -
2010-08-10 02:53:51denverscsettype: behavior
2010-08-10 02:03:20denversccreate