[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Roundup Robot]

Roundup Robot added the comment:

New changeset 5e8ef1493843 by Victor Stinner in branch '3.6':
Implement rich comparison for _sre.SRE_Pattern
https://hg.python.org/cpython/rev/5e8ef1493843

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[STINNER Victor]

STINNER Victor added the comment:

Note: My issue #26742 has been marked as a duplicate of this one.

I confirm that "./python -Wd -m test -j0 test_warnings" doesn't complain "1 
test altered the execution environment: test_warnings" anymore. Thanks for the 
fix.

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Martin Panter added the comment:

I eliminated initial_len from my final version.

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Roundup Robot]

Roundup Robot added the comment:

New changeset f57f4e33ba5e by Martin Panter in branch '3.5':
Issue #18383: Avoid adding duplicate filters when warnings is reloaded
https://hg.python.org/cpython/rev/f57f4e33ba5e

New changeset 90bb91be6f3b by Martin Panter in branch 'default':
Issue #18383: Merge warnings fix from 3.5
https://hg.python.org/cpython/rev/90bb91be6f3b

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

LGTM, except that initial_len is now always 0.

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Martin Panter added the comment:

New patch with common _add_filters() function, and added resetwarnings() calls 
to avoid the conflict with pre-defined filters.

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

$ ./python -We::UserWarning -m test.regrtest test_warnings
Run tests sequentially
0:00:00 [1/1] test_warnings
/home/serhiy/py/cpython/Lib/test/test_warnings/__init__.py:108: UserWarning: 
FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
/home/serhiy/py/cpython/Lib/test/test_warnings/__init__.py:108: UserWarning: 
FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
test test_warnings failed -- multiple errors occurred; run in verbose mode for 
details
test_warnings failed
1 test failed:
test_warnings
Total duration: 0:00:02

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Berker Peksag]

Berker Peksag added the comment:

LGTM

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Martin Panter added the comment:

Forgot to refresh my patch

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Changes by Martin Panter :


Removed file: http://bugs.python.org/file42937/issue18383_avoid_dups_3.diff

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Martin Panter added the comment:

I am inclined to go with Alex’s patch. I am uploading a new version of it, 
issue18383_avoid_dups_3.diff, which resolves conflicts with recent changes.

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[STINNER Victor]

STINNER Victor added the comment:

> Revision c1396d28c440 looks like it may help. Possibly with the 3.5+ 
> assertWarns() half of the problem; I’ll have to have a closer look later.

Oh, I wasn't aware of this issue. Good to know that I contributed to it :-)

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Martin Panter added the comment:

Okay so I take back my first proposal of restoring the filters in the test 
suite, which would bring us back to 
.

Also, my second proposal of setting a flag doesn’t look so easy either. The 
“_warnings” C module caches the filters list in a static variable between 
module reloads, so it is not so easy to keep a flag recording whether the 
“warnings” Python module needs to initialize it. I started on a patch, but 
discovered I would have to make uncomfortable changes to the C module.

So unless anyone has any better ideas, I think Alex’s patch is as good and 
practical enough. And yes Victor’s change does fix the other half of the 
problem.

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[issue18383] test_warnings modifies warnings.filters when running with "-W default"

[Martin Panter]

Martin Panter added the comment:

Revision c1396d28c440 looks like it may help. Possibly with the 3.5+ 
assertWarns() half of the problem; I’ll have to have a closer look later.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Martin Panter]

Martin Panter added the comment:

Florent’s manual reproducer is fixed by issue18383_34_2.diff, as is 
test___all__. And I think the new logic for changing the priority of the filter 
entries might be sound now. But it does seem like we are adding unnecessary 
complexity to the implementation just to avoid a quirk of the test suite. Maybe 
it would be better to save and restore the original filters in the test suite, 
with a comment explaining why. Or perhaps set a _warnings._options_processed 
flag to prevent the double initialization?

FTR Alex already hinted at this, but I only now realize 
issue18383_assert_warns_and_dups_v2.patch contains extra fixes for 
assertWarns() that are only applicable to 3.5+. They are basically a followup 
of Issue 16382 and Issue 23027, rather than the original issue here, although 
the symptom is almost the same.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

This is updated patch that doesn't alter warn_explicit behavior.

So the following:
simplefilter(ignore)
simplefilter(error, append=True)
simplefilter(ignore, append=True)

will ignore all warnings with this patch and no duplicates are inserted to 
warnings.filters. Also added a test for that case.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

@rbcollins that is exactly what was trying to say in previous comment. We can 
make a change to current patch that won't affect behavior. In old API in this 
sequence of filters last filter was never used:

simplefilter(ignore)
simplefilter(error, append=True)
simplefilter(ignore, append=True)  # never used

So I suggest that new patch should work like this:


simplefilter(error)
simplefilter(ignore, append=True)  # appends new filter to the end

simplefilter(ignore)
simplefilter(error, append=True)
simplefilter(ignore, append=True)  # does nothing since same filter is 
present.

This way filtering will work in the same way it worked before patch and we 
won't have duplicates.

I'll update the patch as soon as I will get to my computer.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Robert Collins]

Robert Collins added the comment:

@ashkop so append=True could be clearer as 'atend=True' - both forms of call 
are expected to add the filter, but one adds to the front, one to the end.

Looking at warn_explicit, its takes the first matching filter, and then acts on 
its action.

So the following:
simplefilter(ignore)
simplefilter(error, append=True)
simplefilter(ignore, append=True)

will ignore all warnings today.

With this patch it will error on all warnings.

So at *best* I think this is a breaking API change.

Old:
 from warnings import simplefilter, warn
 simplefilter(ignore)
 simplefilter(error, append=True)
 simplefilter(ignore, append=True)
 warn(boo)
 

With this patch:
 from warnings import simplefilter, warn
 simplefilter(ignore)
 simplefilter(error, append=True)
 simplefilter(ignore, append=True)
 warn(boo)
Traceback (most recent call last):
  File stdin, line 1, in module
UserWarning: boo
 

Now, perhaps its desirable to make this change. I haven't decided yet about the 
tastefulness of the new API, but if we do we're going to need docstring 
updates, and API doc changes to match it.

Since the goal here is to fix module reloads, I think the right way to do that 
is to only change the module initialisation code.

e.g. add an optional 'no_duplicate' parameter to simplefilter and use that from 
the module initialisation. Thats backwards compatible and opt-in. If we don't 
think it should be public, make it a _ prefixed parameter. I think it would be 
fine to be public though.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

Looking at this patch again, I'm wondering if it is correct to remove duplicate 
filter if append=True. Perhaps in this case it is more correct to leave the 
filter in place and do not append new one?

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Berker Peksag]

Berker Peksag added the comment:

Here is an updated patch (against 3.4 branch). I've just made some small 
cosmetic changes and split the test into two parts (filterwarnings and 
simplefilter). Patch looks reasonable to me, but it would be nice to get a 
second opinion.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Martin Panter]

Martin Panter added the comment:

FWIW there is a new message currently being triggered by test___all__. The 
patch here also stops this message.

$ hg update 4335d898be59
$ ./python -bWall -m test test___all__
[1/1] test___all__
Warning -- warnings.filters was modified by test___all__
1 test altered the execution environment:
test___all__

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

Please, review the patch.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

*ping*

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

Removed unnecessary assertWarns() contexts and fixed spelling errors.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Martin Panter]

Martin Panter added the comment:

issue18383_assert_warns_and_dups.patch fixes all my new test suite complaints, 
and removes the message about altering warnings.filters.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Martin Panter]

Martin Panter added the comment:

I tried issue18383_remove_dups_and_test.patch, but it doesn’t seem to fix the 
problem, and causes new test failures and warnings. Let me know if you want 
more info. Existing messages that I thought this was meant to fix:

[372/393/5] test_warnings
/media/disk/home/proj/python/cpython/Lib/test/test_warnings.py:100: 
UserWarning: FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
/media/disk/home/proj/python/cpython/Lib/test/test_warnings.py:100: 
UserWarning: FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
Warning -- warnings.filters was modified by test_warnings
[. . .]
1 test altered the execution environment:
test_warnings

Three new failures:

[ 12/393/1] test___all__
test test___all__ failed -- Traceback (most recent call last):
  File /media/disk/home/proj/python/cpython/Lib/test/test___all__.py, line 
105, in test_all
self.check_all(modname)
  File /media/disk/home/proj/python/cpython/Lib/test/test___all__.py, line 
28, in check_all
raise FailedImport(modname)
  File /media/disk/home/proj/python/cpython/Lib/contextlib.py, line 66, in 
__exit__
next(self.gen)
  File /media/disk/home/proj/python/cpython/Lib/test/support/__init__.py, 
line 1124, in _filterwarnings
raise AssertionError(unhandled warning %s % reraise[0])
AssertionError: unhandled warning {message : 
DeprecationWarning('stat_float_times() is deprecated',), category : 
'DeprecationWarning', filename : 
'/media/disk/home/proj/python/cpython/Lib/test/test_os.py', lineno : 75, line : 
None}
[. . .]
[147/393/3] test_global
test test_global failed -- multiple errors occurred; run in verbose mode for 
details
[. . .]
[240/393/5] test_pkgutil
test test_pkgutil failed -- Traceback (most recent call last):
  File /media/disk/home/proj/python/cpython/Lib/test/test_pkgutil.py, line 
327, in test_importer_deprecated
x = pkgutil.ImpImporter()
  File /media/disk/home/proj/python/cpython/Lib/contextlib.py, line 66, in 
__exit__
next(self.gen)
  File /media/disk/home/proj/python/cpython/Lib/test/support/__init__.py, 
line 1124, in _filterwarnings
raise AssertionError(unhandled warning %s % reraise[0])
AssertionError: unhandled warning {message : PendingDeprecationWarning(the imp 
module is deprecated in favour of importlib; see the module's documentation for 
alternative uses,), category : 'PendingDeprecationWarning', filename : 
'/media/disk/home/proj/python/cpython/Lib/importlib/_bootstrap.py', lineno : 
321, line : None}
[. . .]
5 tests failed:
test___all__ test_distutils test_gdb test_global test_pkgutil

(Ignore distutils and GDB; they normally fail for me.) New warnings, though I 
suspect they may be a side effect and not entirely the fault of the patch:

[ 18/393/1] test_unittest
[163/393/4] test_imp
[169/393/4] test_importlib
[205/393/4] test_modulefinder
[220/393/4] test_os
[241/393/5] test_platform
[329/393/5] test_threaded_import
[354/393/5] test_unicode

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

So, there are actually two issues, both of them causing the original warning. 

First issue was pointed out by Florent Xicluna. warnings.filterwarnings() 
method can create duplicates in warnings.filters.

Second issue is that assertWarns() works incorrectly in test_warnings.py due to 
use of import_fresh_module(). This produced original warning even without -Wd 
flag.

I attached a patch that fixes both issues for review. It includes a fix of 
previous patch, so no new warnings are produced. But perhaps we should separate 
these issues and create two patches.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

When caller adds duplicate filter maybe we should promote his filter to the 
beginning of filters list? This feels more correct to me. So if user adds 
duplicate filter everything will work as if we added it.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Berker Peksag]

Berker Peksag added the comment:

issue18383_remove_dups.patch looks good to me. A test would be nice.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Serhiy Storchaka]

Changes by Serhiy Storchaka storch...@gmail.com:


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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Martin Panter]

Changes by Martin Panter vadmium...@gmail.com:


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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Alex Shkop]

Alex Shkop added the comment:

The issue occurs only if C implementation of _warnings is available. It is 
caused by re-use of global filters variable from _warnings when warnings is 
being re-imported.
So warnings modifies _warnings.filters on first import. Then, when you import 
warnings again it uses already modified version of _warnings.filters and adds 
same filter for the second time.

I attach a simple patch that prevents duplicates in filters. I'm not sure if 
this is a best way to fix the problem, but it works. It certainly affects 
performance of filterwarnings(), but there shouldn't be a lot of filters anyway.

Making filters a set() will solve the problem also, but will require API 
changes. Although I didn't find anywhere in documentation that warnings.filters 
should be a list, someone might rely on its .append() method.

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Added file: http://bugs.python.org/file38301/issue18383_remove_dups.patch

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

The patch fixes symptoms. It would be better to fix the cause of the issue -- 
warnings.filters shouldn't duplicate after module reloading.

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versions: +Python 3.5 -Python 3.3

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Ezio Melotti]

Ezio Melotti added the comment:

LGTM

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Terry J. Reedy]

Changes by Terry J. Reedy tjre...@udel.edu:


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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Florent Xicluna]

New submission from Florent Xicluna:

Running the test suite with -Wd, we got the warning:

[247/375] test_warnings
Warning -- warnings.filters was modified by test_warnings



This is how to reproduce:

./python -Wd

import warnings
from test import support

saved = warnings.filters.copy()

c_warnings = support.import_fresh_module('warnings', fresh=['_warnings'])

saved == warnings.filters
# -- False

--
components: Tests
messages: 192441
nosy: flox
priority: low
severity: normal
stage: needs patch
status: open
title: test_warnings modifies warnings.filters when running with -W default
type: behavior
versions: Python 3.3, Python 3.4

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Florent Xicluna]

Florent Xicluna added the comment:

Much simpler:

$ ./python -Wd

import warnings
import sys
saved = warnings.filters.copy()

del sys.modules['warnings']
import warnings

assert warnings.filters != saved
assert warnings.filters.pop(0) = warnings.filters[0]
assert warnings.filters == saved

Explanation: the default filter is duplicated on each reload of the warnings 
module.

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[issue18383] test_warnings modifies warnings.filters when running with -W default

[Florent Xicluna]

Florent Xicluna added the comment:

This patch fixes the issue.

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keywords: +patch
stage: needs patch - patch review
Added file: 
http://bugs.python.org/file30817/issue18383_test_warnings_filters.diff

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