Adjusted tests.

sundial/fields.py

@@ -84,32 +84,21 @@ def get_db_prep_value(self, value, connection, prepared=False):
         if value is None or hasattr(value, 'resolve_expression'):
             return value
 
-        if settings.USE_TZ:
-            if connection.features.supports_timezones:
-                # XXX: Investigate how to deal with PostgreSQL.
-                pass
-            elif timezone.is_aware(value):
-                value = timezone.make_naive(value, self.db_tzinfo)
-            else:
-                # Allow naive datetime to be provided and assume they are
-                # in db_timezone.
-                pass
-        else:
-            # If timezone support is turned off then it's assumed naive
-            # datetimes are passed in the expected timezone.
-            value = super(DateTimeField, self).get_db_prep_value(value, connection, prepared)
+        if (settings.USE_TZ and
+                not connection.features.supports_timezones and timezone.is_aware(value)):
+            return timezone.make_naive(value, self.db_tzinfo)
 
-        return value
+        return super(DateTimeField, self).get_db_prep_value(value, connection, prepared)
 
     def from_db_value(self, value, expression, connection, context=None):
-        if settings.USE_TZ:
-            if connection.features.supports_timezones:
-                # XXX: Investigate how to deal with PostgreSQL.
-                pass
-            else:
-                # Strip the tzinfo because it will be returned in the
-                # connection's timezone.
-                value = timezone.make_aware(value.replace(tzinfo=None), self.db_tzinfo)
-        else:
-            value = super(DateTimeField, self).from_db_value(value, expression, connection)
+        if value is None:
+            return value
+
+        if settings.USE_TZ and not connection.features.supports_timezones:
+            # At this point the value will be in the connection's timezone
+            # even if it's actually stored using self.db_timezone.
+            # Strip the bogus timezone assignment, make it aware in the
+            # appropriate timezone, and convert it it back to UTC.
+            value = timezone.make_aware(value.replace(tzinfo=None), self.db_tzinfo).astimezone(timezone.utc)
+
         return value

tests/test_fields/models.py

@@ -2,6 +2,7 @@
 
 from django.conf import settings
 from django.db import models
+from django.utils.encoding import python_2_unicode_compatible
 
 from sundial.fields import DateTimeField, TimezoneField
 
@@ -12,5 +13,12 @@ class TimezoneModel(models.Model):
     null_timezone = TimezoneField(blank=True, null=True)
 
 
+@python_2_unicode_compatible
 class DbTimezoneModel(models.Model):
     datetime = DateTimeField(db_timezone='Europe/Amsterdam')
+
+    class Meta:
+        ordering = ('pk',)
+
+    def __str__(self):
+        return str(self.datetime)

tests/test_fields/tests.py

@@ -82,6 +82,17 @@ def test_choices_formfield(self):
 
 
 class DateTimeFieldTests(TestCase):
+    naive_datetime = datetime(2018, 1, 1)
+    aware_datetime = timezone.make_aware(datetime(2018, 1, 1), pytz.timezone('Europe/Amsterdam'))
+
+    @classmethod
+    def setUpTestData(cls):
+        cls.naive_object = DbTimezoneModel.objects.create(datetime=cls.naive_datetime)
+        with override_settings(USE_TZ=True, TIME_ZONE='UTC'):
+            cls.utc_object = DbTimezoneModel.objects.create(datetime=cls.aware_datetime)
+        with override_settings(USE_TZ=True, TIME_ZONE='Europe/Paris'):
+            cls.paris_object = DbTimezoneModel.objects.create(datetime=cls.aware_datetime)
+
     def assert_deconstruct_db_timezone(self, field, expected_db_timezone):
         name, path, args, kwargs = field.deconstruct()
         self.assertEqual(name, 'field')
@@ -98,10 +109,45 @@ def test_deconstruct(self):
         field = DateTimeField(name='field', db_timezone='Europe/Amsterdam')
         self.assert_deconstruct_db_timezone(field, 'Europe/Amsterdam')
 
-    @override_settings(USE_TZ=True, TIME_ZONE='UTC')
-    def test_database_roundtrip(self):
-        tzinfo = pytz.timezone('Europe/Amsterdam')
-        aware_datetime = timezone.make_aware(datetime(2018, 1, 1), tzinfo)
-        obj = DbTimezoneModel.objects.create(datetime=aware_datetime)
-        obj.refresh_from_db()
-        self.assertEqual(obj.datetime, aware_datetime)
+    def test_retreival(self):
+        self.naive_object.refresh_from_db()
+        self.assertEqual(self.naive_object.datetime, self.naive_datetime)
+        self.utc_object.refresh_from_db()
+        self.assertEqual(self.utc_object.datetime, self.naive_datetime)
+        with override_settings(USE_TZ=True, TIME_ZONE='UTC'):
+            utc = timezone.get_current_timezone()
+            self.naive_object.refresh_from_db()
+            self.assertEqual(self.naive_object.datetime, self.aware_datetime)
+            self.assertEqual(self.naive_object.datetime.tzinfo, utc)
+            self.utc_object.refresh_from_db()
+            self.assertEqual(self.utc_object.datetime, self.aware_datetime)
+            self.assertEqual(self.utc_object.datetime.tzinfo, utc)
+            self.paris_object.refresh_from_db()
+            self.assertEqual(self.paris_object.datetime, self.aware_datetime)
+            self.assertEqual(self.paris_object.datetime.tzinfo, utc)
+        with override_settings(USE_TZ=True, TIME_ZONE='Europe/Paris'):
+            self.naive_object.refresh_from_db()
+            self.assertEqual(self.naive_object.datetime, self.aware_datetime)
+            self.assertEqual(self.naive_object.datetime.tzinfo, utc)
+            self.utc_object.refresh_from_db()
+            self.assertEqual(self.utc_object.datetime, self.aware_datetime)
+            self.assertEqual(self.utc_object.datetime.tzinfo, utc)
+            self.paris_object.refresh_from_db()
+            self.assertEqual(self.paris_object.datetime, self.aware_datetime)
+            self.assertEqual(self.paris_object.datetime.tzinfo, utc)
+
+    def test_lookup(self):
+        self.assertSequenceEqual(
+            DbTimezoneModel.objects.filter(datetime=self.naive_datetime),
+            [self.naive_object, self.utc_object, self.paris_object],
+        )
+        with override_settings(USE_TZ=True, TIME_ZONE='UTC'):
+            self.assertSequenceEqual(
+                DbTimezoneModel.objects.filter(datetime=self.aware_datetime),
+                [self.naive_object, self.utc_object, self.paris_object],
+            )
+        with override_settings(USE_TZ=True, TIME_ZONE='Europe/Paris'):
+            self.assertSequenceEqual(
+                DbTimezoneModel.objects.filter(datetime=self.aware_datetime),
+                [self.naive_object, self.utc_object, self.paris_object],
+            )