[Python-Dev] test___all__ polluting sys.modules?

Nick Coghlan ncoghlan at gmail.com
Sun Dec 30 02:34:23 CET 2012

On Sun, Dec 30, 2012 at 10:46 AM, Benjamin Peterson <benjamin at python.org> wrote:
> 2012/12/29 Eli Bendersky <eliben at gmail.com>:
>> Hi,
>> This came up while investigating some test-order-dependency failures in
>> issue 16076.
>> test___all__ goes over modules that have `__all__` in them and does 'from
>> <module> import *' on them. This leaves a lot of modules in sys.modules,
>> which may interfere with some tests that do fancy things with sys,modules.
>> In particular, the ElementTree tests have trouble with it because they
>> carefully set up the imports to get the C or the Python version of etree
>> (see issues 15083 and 15075).
>> Would it make sense to save the sys.modules state and restore it in
>> test___all__ so that sys.modules isn't affected by this test?
> Sounds reasonable to me.

I've tried this as an inherent property of regrtest before (to resolve
some problems with test_pydoc), and it didn't work - we have too many
modules with non-local side effects (IIRC, mostly related to the copy
and pickle registries).

Given that it checks the whole standard library, test___all__ is
likely to run into the same problem.

Hence test.support.import_fresh_module - it can ensure you get the
module you want, regardless of the preexisting contents of
sys.modules. (http://docs.python.org/dev/library/test#test.support.import_fresh_module)


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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