Restore all ptr_id attributes with multi table inheritance

A model/table with multi table inheritance has field_ptr_id for the relationship to the parent model - this should be restored when deserializing.

modelcluster/models.py

@@ -56,11 +56,16 @@ def get_serializable_data_for_fields(model):
 
 def model_from_serializable_data(model, data, check_fks=True, strict_fks=False):
     pk_field = model._meta.pk
-    # If model is a child via multitable inheritance, use parent's pk
+    kwargs = {}
+
+    # If model is a child via multitable inheritance, we need to set ptr_id fields all the way up
+    # to the main PK field, as Django won't populate these for us automatically.
     while pk_field.remote_field and pk_field.remote_field.parent_link:
+        kwargs[pk_field.attname] = data['pk']
         pk_field = pk_field.remote_field.model._meta.pk
 
-    kwargs = {pk_field.attname: data['pk']}
+    kwargs[pk_field.attname] = data['pk']
+
     for field_name, field_value in data.items():
         try:
             field = model._meta.get_field(field_name)

tests/tests/test_serialize.py

@@ -7,8 +7,8 @@
 from django.test import TestCase
 from django.utils import timezone
 
-from tests.models import Band, BandMember, Album, Restaurant, Dish, MenuItem, Chef, Wine, \
-    Review, Log, Document, Article, Author, Category
+from tests.models import Band, BandMember, Album, Place, Restaurant, SeafoodRestaurant, Dish, \
+    MenuItem, Chef, Wine, Review, Log, Document, Article, Author, Category
 
 
 class SerializeTest(TestCase):
@@ -112,6 +112,15 @@ def test_deserialize_with_multi_table_inheritance(self):
         self.assertEqual(fat_duck.serves_hot_dogs, False)
         self.assertEqual(fat_duck.reviews.all()[0].author, "Michael Winner")
 
+    def test_deserialize_with_second_level_multi_table_inheritance(self):
+        oyster_club = SeafoodRestaurant.from_json('{"pk": 43, "name": "The Oyster Club"}')
+        self.assertEqual(oyster_club.id, 43)
+        self.assertEqual(oyster_club.restaurant_ptr_id, 43)
+        self.assertEqual(oyster_club.place_ptr_id, 43)
+        self.assertEqual(oyster_club.restaurant_ptr.__class__, Restaurant)
+        self.assertEqual(oyster_club.place_ptr.__class__, Place)
+        self.assertEqual(oyster_club.name, "The Oyster Club")
+
     def test_dangling_foreign_keys(self):
         heston_blumenthal = Chef.objects.create(name="Heston Blumenthal")
         snail_ice_cream = Dish.objects.create(name="Snail ice cream")