QuerySet first() method gives Cannot filter a query once a slice has been taken.

[makinacorpus]

QuerySet first() method gives Cannot filter a query once a slice has been taken.

[Gagaro]

0.4.2 has been released with the fix.

[Gagaro]

Thanks for the report, I fixed it in master but I don't have the time to do a release right now. It will be for next week now.

[AndreasBackx]

@ewen we are aware of the issue and it'll get fixed in #77 as well.

[elmehalawi]

This is happening to me as well, but it's happening for pretty much most of my queries. I'm not sure if it's conflicting with some other library, but even something as simple as:

Item.objects.all()

results in an AssertionError: Cannot filter a query once a slice has been taken. I'm not sure what could be causing this.

[Gagaro]

Does it work with the PR #77 ?

[ciarancourtney]

@Gagaro I was getting this error for only some models in Django 1.11, error disappeared when I used PR #77

[AndreasBackx]

@ciarancourtney we're just waiting for a reply from @glemmaPaul and a follow-up commit and squash so it can be merged.

[ciarancourtney]

Actually I'm still getting this error with the latest PR for many of my test cases, mostly any test that gets an a instance like:

MyModel.objects.all()[0]

will give a stacktrace:

  File "/opt/master/venv/lib/python3.6/site-packages/django/db/models/query.py", line 289, in __getitem__
    return list(qs)[0]
  File "/opt/master/venv/lib/python3.6/site-packages/django/db/models/query.py", line 250, in __iter__
    self._fetch_all()
  File "/opt/master/venv/lib/python3.6/site-packages/safedelete/queryset.py", line 125, in decorator
    self._filter_visibility()
  File "/opt/master/venv/lib/python3.6/site-packages/safedelete/queryset.py", line 100, in _filter_visibility
    "Cannot filter a query once a slice has been taken."
AssertionError: Cannot filter a query once a slice has been taken.

The admin changelist pages that were failing before are fine with the latest PR though

[ciarancourtney]

Replacing all .all()[0] querysets with .first() resolved my test failures. My codebase was originally written in Django 1.3, so I guess before first() was introduced in Django 1.6, it was acceptable to iterate querysets by index?

[AndreasBackx]

@ciarancourtney I was just thinking of that edge case. We should add tests for those as well.

[ewen]

I get this error using the Django REST Framework JSON API Pagination alongside safedelete, I guess it takes a slice at the pagination page size. Tested it against PR #77 but still fails.

I think it performs the slice here https://github.com/django/django/blob/master/django/core/paginator.py#L57 as it looks to be using the django.core.paginator.

[glemmaPaul]

@AndreasBackx this might be something we can solve by adding our functionality on the iterator() func, this is getting called when these slices happen.

[AndreasBackx]

@glemmaPaul would adding 'iterator' to the evaluation_methods not do the job then?

[elmehalawi]

Any news on this? I'm still experiencing this bug.

[AndreasBackx]

@dublinus See #77

[elmehalawi]

@AndreasBackx I swear I tried this before and it didn't work. But it does now, thanks.

Is this PR going to be merged?

[elmehalawi]

Love this library, thanks guys.

[lanterno]

I'm getting the same error with earliest, and latest queries. Can someone reopen -needs permission-this issue, or should I create a new one?

• I'm using version 0.4.3 and tested with django 1.11 and 2.0

@glemmaPaul @Gagaro

[glemmaPaul]

Thanks @Gagaro for the catch up on this, appreciate it a lot!

[Gagaro]

0.4.4 has been released