[1.8.x] Fixed #24698, #24712 -- Added ForeignKey.get_db_prep_value()

Fixed crashes with ForeignKey to UUIDField and inheritance with UUIDField
primary keys.

django/db/models/fields/related.py

@@ -1939,6 +1939,9 @@ class ForeignKey(ForeignObject):
         else:
             return self.related_field.get_db_prep_save(value, connection=connection)
 
+    def get_db_prep_value(self, value, connection, prepared=False):
+        return self.related_field.get_db_prep_value(value, connection, prepared)
+
     def value_to_string(self, obj):
         if not obj:
             # In required many-to-one fields with only one available choice,

docs/releases/1.8.2.txt

@@ -20,3 +20,8 @@ Bugfixes
 
 * Fixed incorrect GROUP BY clause generation on MySQL when the query's model
   has a self-referential foreign key (:ticket:`24748`).
+
+* Implemented ``ForeignKey.get_db_prep_value()`` so that ``ForeignKey``\s
+  pointing to :class:`~django.db.models.UUIDField` and inheritance on models
+  with ``UUIDField`` primary keys work correctly (:ticket:`24698`,
+  :ticket:`24712`).

tests/model_fields/models.py

@@ -375,3 +375,11 @@ class PrimaryKeyUUIDModel(models.Model):
 
 class RelatedToUUIDModel(models.Model):
     uuid_fk = models.ForeignKey('PrimaryKeyUUIDModel')
+
+
+class UUIDChild(PrimaryKeyUUIDModel):
+    pass
+
+
+class UUIDGrandchild(UUIDChild):
+    pass

tests/model_fields/test_uuid.py

@@ -6,7 +6,8 @@ from django.db import models
 from django.test import TestCase
 
 from .models import (
-    NullableUUIDModel, PrimaryKeyUUIDModel, RelatedToUUIDModel, UUIDModel,
+    NullableUUIDModel, PrimaryKeyUUIDModel, RelatedToUUIDModel, UUIDGrandchild,
+    UUIDModel,
 )
 
 
@@ -146,3 +147,7 @@ class TestAsPrimaryKey(TestCase):
         RelatedToUUIDModel.objects.update(uuid_fk=u2.pk)
         r.refresh_from_db()
         self.assertEqual(r.uuid_fk, u2)
+
+    def test_two_level_foreign_keys(self):
+        # exercises ForeignKey.get_db_prep_value()
+        UUIDGrandchild().save()