#17758: Do not depend on dict order in test suite
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Reporter: lrekucki | Owner: nobody
Type: Bug | Status: new
Component: Core (Other) | Version: 1.3
Severity: Release blocker | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by lrekucki):
OK, I found 2 major bugs so far:
1) {{{django.test.simple.dependency_order()}}}
There are two problems here:
a) The result of this functions depends on the order of aliases for given
DB signature (which in turn depends on the order in settings.DATABASES
dict) - i.e. if you have a DB with aliases {{{["A", "B"]}}} and "A"
depends on "B" then it will raise an error. If the alias list is ["B",
"A"] it will pass (I think it should always fail, right?).
b) The way setup_databases() in the runner treat databases with no
{{{NAME}}} - they get the same signature. There's a special case later to
fix this, but it messes up dependency_order(). In particular, the Django
test suite has two DBs: "default" and "other". If they're assigned the
same test_signature, they're treated as aliases (which isn't correct). As
documented, the "other" database has an implicit dependency on "default"
because we gave no explicit {{{TEST_DEPENDENCIES}}}. And that's how we
arrive at a).
So right now, you have about 50% chance of even running the test suite ;)
I don't have a patch for a general case yet. ATM, I modified the backend
code to return NaN instead of empty string for databases with no
{{{NAME}}}, which prevents them from being aliases. This should also be
the case for SQLite databases where {{{NAME == ":memory:"}}}. And of
course, {{{dependency_order()}}} needs fixing.
2) An ORM bug
{{{
FAIL: test_tickets_8921_9188 (regressiontests.queries.tests.Queries6Tests)
----------------------------------------------------------------------
Traceback (most recent call last):
File
"/home/lrekucki/django/django_lqc/tests/regressiontests/queries/tests.py",
line 1443, in test_tickets_8921_9188
['<Tag: t1>', '<Tag: t4>', '<Tag: t5>']
File "/home/lrekucki/django/django_lqc/django/test/testcases.py", line
774, in assertQuerysetEqual
return self.assertEqual(map(transform, qs), values)
AssertionError: Lists differ: ['<Tag: t4>', '<Tag: t5>'] != ['<Tag: t1>',
'<Tag: t4>', '<T...
}}}
I tracked the problem down to {{{QuerySet.alias_refcount}}} and
{{{QuerySet.split_exclude}}} which assumes a specific order on the former.
The order can be preserved using SortedDict, but there are a few places
that relabel aliases and ruin the order, like
{{{QuerySet.change_aliases()}}}. (this iterates through {{{change_map}}}
argument which is a dictionary, so the new aliases are inserted in random
order). I fixed this, by using {{{change_map = SortedDict()}}} in
{{{QuerySet.split_exclude}}}. This should probably apply to all
{{{change_map}}}s when working with aliases.
--
Ticket URL: <https://code.djangoproject.com/ticket/17758#comment:2>
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