[1.9.x] Fixed #25807 -- Instructed the migration writer about lazy objects.

Thanks to Trac alias mrgaolei for the report, Baptiste for the confirmation
and Tim for the review.

Backport of cc2ca9c550fbf8fca8684b373a3c8e3618eea08e from master

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/migrations/test_writer.py b/tests/migrations/test_writer.py
index 12df772df5..b3c41565e3 100644
--- a/tests/migrations/test_writer.py
+++ b/tests/migrations/test_writer.py
@@ -23,6 +23,7 @@ from django.test import SimpleTestCase, ignore_warnings, mock
 from django.utils import datetime_safe, six
 from django.utils._os import upath
 from django.utils.deconstruct import deconstructible
+from django.utils.functional import SimpleLazyObject
 from django.utils.timezone import FixedOffset, get_default_timezone, utc
 from django.utils.translation import ugettext_lazy as _
 
@@ -229,6 +230,11 @@ class WriterTests(SimpleTestCase):
             ("[list, tuple, dict, set, frozenset]", set())
         )
 
+    def test_serialize_lazy_objects(self):
+        pattern = re.compile(r'^foo$', re.UNICODE)
+        lazy_pattern = SimpleLazyObject(lambda: pattern)
+        self.assertEqual(self.serialize_round_trip(lazy_pattern), pattern)
+
     def test_serialize_functions(self):
         with six.assertRaisesRegex(self, ValueError, 'Cannot serialize function: lambda'):
             self.assertSerializedEqual(lambda x: 42)