Refs #18586 -- Split up tests.defer.DeferTests.test_defer

tests/defer/tests.py

@@ -6,155 +6,203 @@ from django.test import TestCase
 from .models import Secondary, Primary, Child, BigChild, ChildProxy, RefreshPrimaryProxy
 
 
-class DeferTests(TestCase):
+class AssertionMixin(object):
     def assert_delayed(self, obj, num):
+        """
+        Instances with deferred fields look the same as normal instances when
+        we examine attribute values. Therefore, this method returns the number
+        of deferred fields on returned instances.
+        """
         count = 0
         for field in obj._meta.fields:
-            if isinstance(obj.__class__.__dict__.get(field.attname),
-                    DeferredAttribute):
+            if isinstance(obj.__class__.__dict__.get(field.attname), DeferredAttribute):
                 count += 1
         self.assertEqual(count, num)
 
-    def test_defer(self):
-        # To all outward appearances, instances with deferred fields look the
-        # same as normal instances when we examine attribute values. Therefore
-        # we test for the number of deferred fields on returned instances (by
-        # poking at the internals), as a way to observe what is going on.
 
-        s1 = Secondary.objects.create(first="x1", second="y1")
-        p1 = Primary.objects.create(name="p1", value="xx", related=s1)
+class DeferTests(AssertionMixin, TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.s1 = Secondary.objects.create(first="x1", second="y1")
+        cls.p1 = Primary.objects.create(name="p1", value="xx", related=cls.s1)
 
+    def test_defer(self):
         qs = Primary.objects.all()
-
         self.assert_delayed(qs.defer("name")[0], 1)
-        self.assert_delayed(qs.only("name")[0], 2)
+        self.assert_delayed(qs.defer("name").get(pk=self.p1.pk), 1)
         self.assert_delayed(qs.defer("related__first")[0], 0)
+        self.assert_delayed(qs.defer("name").defer("value")[0], 2)
 
+    def test_only(self):
+        qs = Primary.objects.all()
+        self.assert_delayed(qs.only("name")[0], 2)
+        self.assert_delayed(qs.only("name").get(pk=self.p1.pk), 2)
+        self.assert_delayed(qs.only("name").only("value")[0], 2)
+        self.assert_delayed(qs.only("related__first")[0], 2)
         # Using 'pk' with only() should result in 3 deferred fields, namely all
         # of them except the model's primary key see #15494
         self.assert_delayed(qs.only("pk")[0], 3)
-
-        obj = qs.select_related().only("related__first")[0]
-        self.assert_delayed(obj, 2)
-
-        self.assertEqual(obj.related_id, s1.pk)
-
         # You can use 'pk' with reverse foreign key lookups.
-        self.assert_delayed(s1.primary_set.all().only('pk')[0], 3)
+        self.assert_delayed(self.s1.primary_set.all().only('pk')[0], 3)
 
-        self.assert_delayed(qs.defer("name").extra(select={"a": 1})[0], 1)
-        self.assert_delayed(qs.extra(select={"a": 1}).defer("name")[0], 1)
-        self.assert_delayed(qs.defer("name").defer("value")[0], 2)
-        self.assert_delayed(qs.only("name").only("value")[0], 2)
-        self.assert_delayed(qs.only("name").defer("value")[0], 2)
-        self.assert_delayed(qs.only("name", "value").defer("value")[0], 2)
+    def test_defer_only_chaining(self):
+        qs = Primary.objects.all()
+        self.assert_delayed(qs.only("name", "value").defer("name")[0], 2)
+        self.assert_delayed(qs.defer("name").only("value", "name")[0], 2)
         self.assert_delayed(qs.defer("name").only("value")[0], 2)
+        self.assert_delayed(qs.only("name").defer("value")[0], 2)
+
+    def test_defer_on_an_already_deferred_field(self):
+        qs = Primary.objects.all()
+        self.assert_delayed(qs.defer("name")[0], 1)
+        self.assert_delayed(qs.defer("name").defer("name")[0], 1)
 
-        obj = qs.only()[0]
+    def test_defer_none_to_clear_deferred_set(self):
+        qs = Primary.objects.all()
+        self.assert_delayed(qs.defer("name", "value")[0], 2)
         self.assert_delayed(qs.defer(None)[0], 0)
         self.assert_delayed(qs.only("name").defer(None)[0], 0)
 
+    def test_only_none_raises_error(self):
+        msg = 'Cannot pass None as an argument to only().'
+        with self.assertRaisesMessage(TypeError, msg):
+            Primary.objects.only(None)
+
+    def test_defer_extra(self):
+        qs = Primary.objects.all()
+        self.assert_delayed(qs.defer("name").extra(select={"a": 1})[0], 1)
+        self.assert_delayed(qs.extra(select={"a": 1}).defer("name")[0], 1)
+
+    def test_defer_values_does_not_defer(self):
         # User values() won't defer anything (you get the full list of
         # dictionaries back), but it still works.
-        self.assertEqual(qs.defer("name").values()[0], {
-            "id": p1.id,
+        self.assertEqual(Primary.objects.defer("name").values()[0], {
+            "id": self.p1.id,
             "name": "p1",
             "value": "xx",
-            "related_id": s1.id,
+            "related_id": self.s1.id,
         })
-        self.assertEqual(qs.only("name").values()[0], {
-            "id": p1.id,
+
+    def test_only_values_does_not_defer(self):
+        self.assertEqual(Primary.objects.only("name").values()[0], {
+            "id": self.p1.id,
             "name": "p1",
             "value": "xx",
-            "related_id": s1.id,
+            "related_id": self.s1.id,
         })
 
+    def test_get(self):
         # Using defer() and only() with get() is also valid.
-        self.assert_delayed(qs.defer("name").get(pk=p1.pk), 1)
-        self.assert_delayed(qs.only("name").get(pk=p1.pk), 2)
+        qs = Primary.objects.all()
+        self.assert_delayed(qs.defer("name").get(pk=self.p1.pk), 1)
+        self.assert_delayed(qs.only("name").get(pk=self.p1.pk), 2)
 
+    def test_defer_with_select_related(self):
+        obj = Primary.objects.select_related().defer("related__first", "related__second")[0]
+        self.assert_delayed(obj.related, 2)
+        self.assert_delayed(obj, 0)
+
+    def test_only_with_select_related(self):
+        obj = Primary.objects.select_related().only("related__first")[0]
+        self.assert_delayed(obj, 2)
+        self.assert_delayed(obj.related, 1)
+        self.assertEqual(obj.related_id, self.s1.pk)
+        self.assertEqual(obj.name, "p1")
+
+    def test_defer_selected_related_raises_invalid_query(self):
         # When we defer a field and also select_related it, the query is
         # invalid and raises an exception.
         with self.assertRaises(InvalidQuery):
-            qs.only("name").select_related("related")[0]
+            Primary.objects.defer("related").select_related("related")[0]
+
+    def test_only_selected_related_raises_invalid_query(self):
         with self.assertRaises(InvalidQuery):
-            qs.defer("related").select_related("related")[0]
+            Primary.objects.only("name").select_related("related")[0]
 
+    def test_defer_foreign_keys_are_deferred_and_not_traversed(self):
         # With a depth-based select_related, all deferred ForeignKeys are
         # deferred instead of traversed.
         with self.assertNumQueries(3):
-            obj = qs.defer("related").select_related()[0]
+            obj = Primary.objects.defer("related").select_related()[0]
             self.assert_delayed(obj, 1)
-            self.assertEqual(obj.related.id, s1.pk)
+            self.assertEqual(obj.related.id, self.s1.pk)
 
+    def test_saving_object_with_deferred_field(self):
         # Saving models with deferred fields is possible (but inefficient,
         # since every field has to be retrieved first).
-        obj = Primary.objects.defer("value").get(name="p1")
+        Primary.objects.create(name="p2", value="xy", related=self.s1)
+        obj = Primary.objects.defer("value").get(name="p2")
         obj.name = "a new name"
         obj.save()
         self.assertQuerysetEqual(
             Primary.objects.all(), [
-                "a new name",
+                "p1", "a new name",
             ],
-            lambda p: p.name
+            lambda p: p.name,
+            ordered=False,
         )
 
+    def test_defer_baseclass_when_subclass_has_no_added_fields(self):
         # Regression for #10572 - A subclass with no extra fields can defer
         # fields from the base class
-        Child.objects.create(name="c1", value="foo", related=s1)
+        Child.objects.create(name="c1", value="foo", related=self.s1)
         # You can defer a field on a baseclass when the subclass has no fields
         obj = Child.objects.defer("value").get(name="c1")
         self.assert_delayed(obj, 1)
         self.assertEqual(obj.name, "c1")
         self.assertEqual(obj.value, "foo")
-        obj.name = "c2"
-        obj.save()
 
+    def test_only_baseclass_when_subclass_has_no_added_fields(self):
         # You can retrieve a single column on a base class with no fields
-        obj = Child.objects.only("name").get(name="c2")
+        Child.objects.create(name="c1", value="foo", related=self.s1)
+        obj = Child.objects.only("name").get(name="c1")
+        # on an inherited model, its PK is also fetched, hence '3' deferred fields.
         self.assert_delayed(obj, 3)
-        self.assertEqual(obj.name, "c2")
+        self.assertEqual(obj.name, "c1")
         self.assertEqual(obj.value, "foo")
-        obj.name = "cc"
-        obj.save()
 
-        BigChild.objects.create(name="b1", value="foo", related=s1, other="bar")
+
+class BigChildDeferTests(AssertionMixin, TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.s1 = Secondary.objects.create(first="x1", second="y1")
+        BigChild.objects.create(name="b1", value="foo", related=cls.s1, other="bar")
+
+    def test_defer_baseclass_when_subclass_has_added_field(self):
         # You can defer a field on a baseclass
         obj = BigChild.objects.defer("value").get(name="b1")
         self.assert_delayed(obj, 1)
         self.assertEqual(obj.name, "b1")
         self.assertEqual(obj.value, "foo")
         self.assertEqual(obj.other, "bar")
-        obj.name = "b2"
-        obj.save()
 
+    def test_defer_subclass(self):
         # You can defer a field on a subclass
-        obj = BigChild.objects.defer("other").get(name="b2")
+        obj = BigChild.objects.defer("other").get(name="b1")
         self.assert_delayed(obj, 1)
-        self.assertEqual(obj.name, "b2")
+        self.assertEqual(obj.name, "b1")
         self.assertEqual(obj.value, "foo")
         self.assertEqual(obj.other, "bar")
-        obj.name = "b3"
-        obj.save()
 
+    def test_only_baseclass_when_subclass_has_added_field(self):
         # You can retrieve a single field on a baseclass
-        obj = BigChild.objects.only("name").get(name="b3")
+        obj = BigChild.objects.only("name").get(name="b1")
+        # when inherited model, its PK is also fetched, hence '4' deferred fields.
         self.assert_delayed(obj, 4)
-        self.assertEqual(obj.name, "b3")
+        self.assertEqual(obj.name, "b1")
         self.assertEqual(obj.value, "foo")
         self.assertEqual(obj.other, "bar")
-        obj.name = "b4"
-        obj.save()
 
-        # You can retrieve a single field on a baseclass
-        obj = BigChild.objects.only("other").get(name="b4")
+    def test_only_sublcass(self):
+        # You can retrieve a single field on a subclass
+        obj = BigChild.objects.only("other").get(name="b1")
         self.assert_delayed(obj, 4)
-        self.assertEqual(obj.name, "b4")
+        self.assertEqual(obj.name, "b1")
         self.assertEqual(obj.value, "foo")
         self.assertEqual(obj.other, "bar")
-        obj.name = "bb"
-        obj.save()
 
+
+class TestDefer2(AssertionMixin, TestCase):
     def test_defer_proxy(self):
         """
         Ensure select_related together with only on a proxy model behaves