[1.8.x] Fixed #24343 -- Ensure db converters are used for foreign keys.

Joint effort between myself, Josh, Anssi and Shai.

Conflicts:
	django/db/models/query.py
	tests/model_fields/models.py

Backport of 4755f8fc25331c739a6f932cc8aba0cc9e62e352 from master.

2 files changed, 13 insertions, 1 deletions

diff --git a/tests/model_fields/models.py b/tests/model_fields/models.py
index 5f580624ba..3d25c89607 100644
--- a/tests/model_fields/models.py
+++ b/tests/model_fields/models.py
@@ -369,3 +369,7 @@ class NullableUUIDModel(models.Model):
 
 class PrimaryKeyUUIDModel(models.Model):
     id = models.UUIDField(primary_key=True, default=uuid.uuid4)
+
+
+class RelatedToUUIDModel(models.Model):
+    uuid_fk = models.ForeignKey('PrimaryKeyUUIDModel')
diff --git a/tests/model_fields/test_uuid.py b/tests/model_fields/test_uuid.py
index f06f4d02a7..28e11914a1 100644
--- a/tests/model_fields/test_uuid.py
+++ b/tests/model_fields/test_uuid.py
@@ -5,7 +5,9 @@ from django.core import exceptions, serializers
 from django.db import models
 from django.test import TestCase
 
-from .models import NullableUUIDModel, PrimaryKeyUUIDModel, UUIDModel
+from .models import (
+    NullableUUIDModel, PrimaryKeyUUIDModel, RelatedToUUIDModel, UUIDModel,
+)
 
 
 class TestSaveLoad(TestCase):
@@ -121,3 +123,9 @@ class TestAsPrimaryKey(TestCase):
         self.assertTrue(u1_found)
         self.assertTrue(u2_found)
         self.assertEqual(PrimaryKeyUUIDModel.objects.count(), 2)
+
+    def test_underlying_field(self):
+        pk_model = PrimaryKeyUUIDModel.objects.create()
+        RelatedToUUIDModel.objects.create(uuid_fk=pk_model)
+        related = RelatedToUUIDModel.objects.get()
+        self.assertEqual(related.uuid_fk.pk, related.uuid_fk_id)