Queryset gets corrupted when using nested Prefetch

[Marcin]

When queryset objects contains nested Prefetch objects, after first evaluation it gets corrupted.

Im attaching simple example, to reproduce a bug you need to run these commands:

1. Install requirements file
2. python mange.py migrate
3. python manage runserver

Open your browser on:

​http://127.0.0.1:8000/

And refresh twice. First time its gonna work, next time you should get an error:

AttributeError at /
Cannot find 'author' on UserProfile object, 'author__profile__university' is an invalid parameter to prefetch_related()

From my limited investigation it looks like after first evaluation prefetch_to parameter is prepended with previous prefetch_to param, which is in this case not correct.

Temporarly, its enough to create this object (queryset) again every time it gets used.

[Marcin]

Sample project

[Baptiste Mispelon]

Hi,

I can reproduce the issue you're reporting in the 1.8 version but not in 1.9.

I used git bisect and found that 74261bc593bcf9411e7e25a4731dd9471499819e (associated with #24873) is the commit that fixed it.

I'm therefore marking this as a duplicate.

Thanks.