1 files changed, 137 insertions, 0 deletions
diff --git a/parts/django/tests/modeltests/defer/tests.py b/parts/django/tests/modeltests/defer/tests.py
new file mode 100644
index 0000000..5f6c53d
--- /dev/null
+++ b/parts/django/tests/modeltests/defer/tests.py
@@ -0,0 +1,137 @@
+from django.db.models.query_utils import DeferredAttribute
+from django.test import TestCase
+
+from models import Secondary, Primary, Child, BigChild
+
+
+class DeferTests(TestCase):
+    def assert_delayed(self, obj, num):
+        count = 0
+        for field in obj._meta.fields:
+            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)
+
+        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("related__first")[0], 0)
+
+        obj = qs.select_related().only("related__first")[0]
+        self.assert_delayed(obj, 2)
+
+        self.assertEqual(obj.related_id, s1.pk)
+
+        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)
+        self.assert_delayed(qs.defer("name").only("value")[0], 2)
+
+        obj = qs.only()[0]
+        self.assert_delayed(qs.defer(None)[0], 0)
+        self.assert_delayed(qs.only("name").defer(None)[0], 0)
+
+        # 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,
+            "name": "p1",
+            "value": "xx",
+            "related_id": s1.id,
+        })
+        self.assertEqual(qs.only("name").values()[0], {
+            "id": p1.id,
+            "name": "p1",
+            "value": "xx",
+            "related_id": s1.id,
+        })
+
+        # 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)
+
+        # DOES THIS WORK?
+        self.assert_delayed(qs.only("name").select_related("related")[0], 1)
+        self.assert_delayed(qs.defer("related").select_related("related")[0], 0)
+
+        # 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")
+        obj.name = "a new name"
+        obj.save()
+        self.assertQuerysetEqual(
+            Primary.objects.all(), [
+                "a new name",
+            ],
+            lambda p: p.name
+        )
+
+        # 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)
+        # 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()
+
+        # You can retrive a single column on a base class with no fields
+        obj = Child.objects.only("name").get(name="c2")
+        self.assert_delayed(obj, 3)
+        self.assertEqual(obj.name, "c2")
+        self.assertEqual(obj.value, "foo")
+        obj.name = "cc"
+        obj.save()
+
+        BigChild.objects.create(name="b1", value="foo", related=s1, other="bar")
+        # 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()
+
+        # You can defer a field on a subclass
+        obj = BigChild.objects.defer("other").get(name="b2")
+        self.assert_delayed(obj, 1)
+        self.assertEqual(obj.name, "b2")
+        self.assertEqual(obj.value, "foo")
+        self.assertEqual(obj.other, "bar")
+        obj.name = "b3"
+        obj.save()
+
+        # You can retrieve a single field on a baseclass
+        obj = BigChild.objects.only("name").get(name="b3")
+        self.assert_delayed(obj, 4)
+        self.assertEqual(obj.name, "b3")
+        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")
+        self.assert_delayed(obj, 4)
+        self.assertEqual(obj.name, "b4")
+        self.assertEqual(obj.value, "foo")
+        self.assertEqual(obj.other, "bar")
+        obj.name = "bb"
+        obj.save()