Fixed #21037 -- Made MigrationWriter raise a ValueError when serializing lambda functions.

2 files changed, 7 insertions, 2 deletions

diff --git a/django/db/migrations/writer.py b/django/db/migrations/writer.py
index e23f15dd77..fa4afbeabf 100644
--- a/django/db/migrations/writer.py
+++ b/django/db/migrations/writer.py
@@ -152,10 +152,12 @@ class MigrationWriter(object):
                 klass = value.im_class
                 module = klass.__module__
                 return "%s.%s.%s" % (module, klass.__name__, value.__name__), set(["import %s" % module])
+            elif value.__name__ == '<lambda>':
+                raise ValueError("Cannot serialize function: lambda")
+            elif value.__module__ is None:
+                raise ValueError("Cannot serialize function %r: No module" % value)
             else:
                 module = value.__module__
-                if module is None:
-                    raise ValueError("Cannot serialize function %r: No module" % value)
                 return "%s.%s" % (module, value.__name__), set(["import %s" % module])
         # Classes
         elif isinstance(value, type):
diff --git a/tests/migrations/test_writer.py b/tests/migrations/test_writer.py
index ff6fc47737..022628803b 100644
--- a/tests/migrations/test_writer.py
+++ b/tests/migrations/test_writer.py
@@ -60,6 +60,9 @@ class WriterTests(TestCase):
         self.assertSerializedEqual(set([2, 3, "eighty"]))
         self.assertSerializedEqual({"lalalala": ["yeah", "no", "maybe"]})
         self.assertSerializedEqual(_('Hello'))
+        # Functions
+        with six.assertRaisesRegex(self, ValueError, 'Cannot serialize function: lambda'):
+            self.assertSerializedEqual(lambda x: 42)
         # Datetime stuff
         self.assertSerializedEqual(datetime.datetime.utcnow())
         self.assertSerializedEqual(datetime.datetime.utcnow)