Fixed #21438: makemigrations now detects ManyToManyFields

django/db/migrations/state.py

@@ -100,6 +100,10 @@ class ModelState(object):
             name, path, args, kwargs = field.deconstruct()
             field_class = import_by_path(path)
             fields.append((name, field_class(*args, **kwargs)))
+        for field in model._meta.local_many_to_many:
+            name, path, args, kwargs = field.deconstruct()
+            field_class = import_by_path(path)
+            fields.append((name, field_class(*args, **kwargs)))
         # Extract the options
         options = {}
         for name in DEFAULT_NAMES:

tests/migrations/test_state.py

@@ -36,6 +36,7 @@ class StateTests(TestCase):
         class Book(models.Model):
             title = models.CharField(max_length=1000)
             author = models.ForeignKey(Author)
+            contributors = models.ManyToManyField(Author)
 
             class Meta:
                 app_label = "migrations"
@@ -59,9 +60,10 @@ class StateTests(TestCase):
 
         self.assertEqual(book_state.app_label, "migrations")
         self.assertEqual(book_state.name, "Book")
-        self.assertEqual([x for x, y in book_state.fields], ["id", "title", "author"])
+        self.assertEqual([x for x, y in book_state.fields], ["id", "title", "author", "contributors"])
         self.assertEqual(book_state.fields[1][1].max_length, 1000)
         self.assertEqual(book_state.fields[2][1].null, False)
+        self.assertEqual(book_state.fields[3][1].__class__.__name__, "ManyToManyField")
         self.assertEqual(book_state.options, {"verbose_name": "tome", "db_table": "test_tome"})
         self.assertEqual(book_state.bases, (models.Model, ))