AttributeError when calling first()/last() on an unordered queryset performing aggregation and grouping by an annotation

[Jacob Walls]

02eed4f37879b2077496f86bb1378a076b981233 (#36648) assumed all members of a GROUP BY were Cols. That introduced an AttributeError for cases involving a function output like Lower, shown here:

from django.db import models
from django.db.models.functions import Lower

class Person(models.Model):
    name = models.CharField(max_length=100)

def run():
    # Should raise informative TypeError:
    # Cannot use QuerySet.first() on an unordered queryset performing aggregation.
    # Add an ordering with order_by().
    first = (
        Person.objects
        .values("name")
        .annotate(lower=Lower("name"), count=models.Count("id"))
        .first()
    )

  File "/usr/local/lib/python3.12/site-packages/django/db/models/query.py", line 1187, in first
    self._check_ordering_first_last_queryset_aggregation(method="first")
  File "/usr/local/lib/python3.12/site-packages/django/db/models/query.py", line 2330, in _check_ordering_first_last_queryset_aggregation
    {col.target for col in self.query.group_by}
     ^^^^^^^^^^
AttributeError: 'Ref' object has no attribute 'target'

It's introduced in 5.2, but we could consider backporting to 6.1 as a "crashing bug".

[Adhithya Pandiri]

Pull request created: ​https://github.com/django/django/pull/22136

[Jacob Walls]

Please leave the Django Sprints tickets for sprints or other contribution events. Those are reserved for mentorship opportunities within the community. When re-assigning a ticket to yourself that's assigned to someone else, it should be unmodified for the last 6 months. If it's sooner than that, it can be acceptable to comment, politely asking if they are still working on the issue. Do not reassign it to yourself though until they respond.