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Fixed #28096 -- Allowed prefetch calls with ModelIterable subclasses

Regression in 7ec330eeb9.
Thanks Tim Graham for the review.
This commit is contained in:
Claude Paroz 2017-04-19 10:24:22 +02:00
parent dff559ff83
commit 43b4a1618e
4 changed files with 21 additions and 3 deletions

View File

@ -1260,7 +1260,7 @@ class Prefetch:
self.prefetch_through = lookup
# `prefetch_to` is the path to the attribute that stores the result.
self.prefetch_to = lookup
if queryset is not None and queryset._iterable_class is not ModelIterable:
if queryset is not None and not issubclass(queryset._iterable_class, ModelIterable):
raise ValueError('Prefetch querysets cannot use values().')
if to_attr:
self.prefetch_to = LOOKUP_SEP.join(lookup.split(LOOKUP_SEP)[:-1] + [to_attr])

View File

@ -33,3 +33,6 @@ Bugfixes
* Fixed layout of ``ReadOnlyPasswordHashWidget`` (used in the admin's user
change page) (:ticket:`28097`).
* Allowed prefetch calls on managers with custom ``ModelIterable`` subclasses
(:ticket:`28096`).

View File

@ -5,6 +5,7 @@ from django.contrib.contenttypes.fields import (
)
from django.contrib.contenttypes.models import ContentType
from django.db import models
from django.db.models.query import ModelIterable, QuerySet
from django.utils.functional import cached_property
@ -95,6 +96,16 @@ class Qualification(models.Model):
ordering = ['id']
class ModelIterableSubclass(ModelIterable):
pass
class TeacherQuerySet(QuerySet):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self._iterable_class = ModelIterableSubclass
class TeacherManager(models.Manager):
def get_queryset(self):
return super().get_queryset().prefetch_related('qualifications')
@ -105,6 +116,7 @@ class Teacher(models.Model):
qualifications = models.ManyToManyField(Qualification)
objects = TeacherManager()
objects_custom = TeacherQuerySet.as_manager()
def __str__(self):
return "%s (%s)" % (self.name, ", ".join(q.name for q in self.qualifications.all()))

View File

@ -9,8 +9,8 @@ from django.test.utils import CaptureQueriesContext
from .models import (
Author, Author2, AuthorAddress, AuthorWithAge, Bio, Book, Bookmark,
BookReview, BookWithYear, Comment, Department, Employee, FavoriteAuthors,
House, LessonEntry, Person, Qualification, Reader, Room, TaggedItem,
Teacher, WordEntry,
House, LessonEntry, ModelIterableSubclass, Person, Qualification, Reader,
Room, TaggedItem, Teacher, WordEntry,
)
@ -708,6 +708,9 @@ class CustomPrefetchTests(TestCase):
def test_values_queryset(self):
with self.assertRaisesMessage(ValueError, 'Prefetch querysets cannot use values().'):
Prefetch('houses', House.objects.values('pk'))
# That error doesn't affect managers with custom ModelIterable subclasses
self.assertIs(Teacher.objects_custom.all()._iterable_class, ModelIterableSubclass)
Prefetch('teachers', Teacher.objects_custom.all())
def test_to_attr_doesnt_cache_through_attr_as_list(self):
house = House.objects.prefetch_related(