Commit 0c8ac097 authored by Luke Plant's avatar Luke Plant
Browse files

Made negative indexing on QuerySet instances raise an assertion error (previously 

it just returned incorrect results).


git-svn-id: http://code.djangoproject.com/svn/django/trunk@2992 bcc190cf-cafb-0310-a4f2-bffc1f526a37
parent b63157c6

django/db/models/query.py

+3 −0
Original line number Diff line number Diff line
@@ -95,6 +95,9 @@ class QuerySet(object): 


    def __getitem__(self, k):

        "Retrieve an item or slice from the set of results."

        assert (not isinstance(k, slice) and (k >= 0)) \

            or (isinstance(k, slice) and (k.start is None or k.start >= 0) and (k.stop is None or k.stop >= 0)), \

            "Negative indexing is not supported."

        if self._result_cache is None:

            if isinstance(k, slice):

                # Offset:

tests/modeltests/basic/models.py

+10 −0
Original line number Diff line number Diff line
@@ -283,6 +283,16 @@ Traceback (most recent call last): 
    ...

AssertionError: Cannot combine queries once a slice has been taken.



# Negative slices are not supported, due to database constraints.

# (hint: inverting your ordering might do what you need).

>>> Article.objects.all()[-1]

Traceback (most recent call last):

    ...

AssertionError: Negative indexing is not supported.

>>> Article.objects.all()[0:-5]

Traceback (most recent call last):

    ...

AssertionError: Negative indexing is not supported.



# An Article instance doesn't have access to the "objects" attribute.

# That's only available on the class.