Fixed prepare_objects being called before prefetch.

Patch queryset.fetch_all instead of queryset._iterable_class.

Author: iurisilvio

django_qserializer/serialization.py

@@ -1,7 +1,6 @@
 import types
 
 from django.db import models
-from django.db.models.query import ModelIterable
 from django.db.models.manager import BaseManager
 
 
@@ -96,24 +95,19 @@ def serialize(self, objs):
         yield from map(self._serialize_object, objs)
 
 
-class _SerializableModelIterable(ModelIterable):
-    def __iter__(self):
-        data = list(super().__iter__())
-        self.queryset.serializer._prepare_objects(data)
-        yield from data
-
-
 class SerializableQuerySet(models.QuerySet):
     @property
     def serializer(self):
         return getattr(self, '_serializer', None)
 
     def to_serialize(self, serializer=None):
         self._serializer = _resolve_serializer(serializer)
-        # https://github.com/django/django/blob/981a3426cf2f54f5282e79fb7f47726998c87cb2/django/db/models/query.py#L353
-        self._iterable_class = _SerializableModelIterable
         return self._serializer._prepare_queryset(self)
 
+    def _fetch_all(self):
+        super()._fetch_all()
+        self._serializer._prepare_objects(self._result_cache)
+
     def _clone(self):
         c = super()._clone()
         c._serializer = self.serializer

django_qserializer/tests/test_serializer.py

@@ -1,7 +1,7 @@
 import pytest
 
 from django_qserializer import BaseSerializer, serialize
-from django_qserializer.tests.testapp.models import Bus, Company
+from django_qserializer.tests.testapp.models import Bus, Company, Travel
 
 
 @pytest.fixture
@@ -10,7 +10,12 @@ def bus_fixture(db):
     return Bus.objects.create(company=company, plate='BUSER')
 
 
-def test_magic_serialize_method(bus_fixture, db, django_assert_num_queries):
+@pytest.fixture
+def travel_fixture(db, bus_fixture):
+    return Travel.objects.create(bus=bus_fixture)
+
+
+def test_magic_serialize_method(bus_fixture, django_assert_num_queries):
     class S(BaseSerializer):
         select_related = ['company']
 
@@ -24,7 +29,7 @@ def serialize_object(self, bus):
         assert {'company': 'Hurricane Cart'} == bus.serialize()
 
 
-def test_global_serialize(bus_fixture, db, django_assert_num_queries):
+def test_global_serialize(bus_fixture, django_assert_num_queries):
     class S(BaseSerializer):
         select_related = ['company']
 
@@ -42,13 +47,13 @@ def test_global_serialize_empty():
     assert [] == serialize([])
 
 
-def test_serialize_object_not_implemented(bus_fixture, db):
+def test_serialize_object_not_implemented(bus_fixture):
     bus = Bus.objects.to_serialize().first()
     with pytest.raises(NotImplementedError):
         bus.serialize()
 
 
-def test_extras(bus_fixture, db, django_assert_num_queries):
+def test_extras(bus_fixture, django_assert_num_queries):
     class Attr(BaseSerializer):
         select_related = ['company']
 
@@ -91,7 +96,7 @@ def serialize_object(self, obj):
         assert expected == next(serialize([bus]))
 
 
-def test_extras_recursive(bus_fixture, db, django_assert_num_queries):
+def test_extras_recursive(bus_fixture, django_assert_num_queries):
     def city(obj):
         return {
             'city': 'SJK',
@@ -131,3 +136,23 @@ def serialize_object(self, obj):
 
     with django_assert_num_queries(0):
         assert expected == bus.serialize()
+
+
+def test_prepare_objects_after_prefetch(travel_fixture):
+    """
+    Regression test. Prior implementation ran prepare_objects before prefetchs.
+    """
+
+    class S(BaseSerializer):
+        prefetch_related = ['travels']
+
+        def prepare_objects(self, objs):
+            for obj in objs:
+                assert obj._prefetched_objects_cache
+
+        def serialize_object(self, obj):
+            return {
+                'plate': obj.plate,
+            }
+
+    Bus.objects.to_serialize(S).first()

django_qserializer/tests/testapp/models.py

@@ -11,3 +11,7 @@ class Bus(models.Model):
     plate = models.CharField(max_length=10)
     company = models.ForeignKey(Company, on_delete=models.SET_NULL)
     objects = SerializableManager()
+
+
+class Travel(models.Model):
+    bus = models.ForeignKey(Bus, related_name='travels', on_delete=models.SET_NULL)

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = django_qserializer
-version = 0.2.4
+version = 0.2.5
 url = https://github.com/buserbrasil/django-qserializer
 license = MIT
 author = Iuri de Silvio