Allow partial update with polymorphic serializers (#655)

Author: charlieallatson

AUTHORS

@@ -24,3 +24,4 @@ Jason Housley <[email protected]>
 Beni Keller <[email protected]>
 Stas S. <[email protected]>
 Nathanael Gordon <[email protected]>
+Charlie Allatson <[email protected]>

CHANGELOG.md

@@ -26,6 +26,8 @@ any parts of the framework not mentioned in the documentation should generally b
 * Don't swallow `filter[]` params when there are several
 * Fix DeprecationWarning regarding collections.abc import in Python 3.7
 * Allow OPTIONS request to be used on RelationshipView
+* Avoid raising validation error for missing fields on a PATCH
+  request for polymorphic serializers
 
 ### Deprecated
 

example/migrations/0007_artproject_description.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.2 on 2019-06-07 06:46
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('example', '0006_auto_20181228_0752'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='artproject',
+            name='description',
+            field=models.CharField(max_length=100, null=True),
+        ),
+    ]

example/models.py

@@ -153,6 +153,7 @@ class Project(PolymorphicModel):
 
 class ArtProject(Project):
     artist = models.CharField(max_length=30)
+    description = models.CharField(max_length=100, null=True)
 
 
 class ResearchProject(Project):

example/tests/integration/test_polymorphism.py

@@ -2,6 +2,7 @@
 
 import pytest
 from django.urls import reverse
+from rest_framework import status
 
 from example.factories import ArtProjectFactory, ProjectTypeFactory
 
@@ -59,6 +60,22 @@ def test_polymorphism_on_polymorphic_model_detail_patch(single_art_project, clie
     assert new_content['data']['attributes']['artist'] == test_artist
 
 
+def test_patch_on_polymorphic_model_without_including_required_field(single_art_project, client):
+    url = reverse("project-detail", kwargs={'pk': single_art_project.pk})
+    data = {
+        'data': {
+            'id': single_art_project.pk,
+            'type': 'artProjects',
+            'attributes': {
+                'description': 'New description'
+            }
+        }
+    }
+    response = client.patch(url, data)
+    assert response.status_code == status.HTTP_200_OK
+    assert response.json()['data']['attributes']['description'] == 'New description'
+
+
 def test_polymorphism_on_polymorphic_model_list_post(client):
     test_topic = 'New test topic {}'.format(random.randint(0, 999999))
     test_artist = 'test-{}'.format(random.randint(0, 999999))

rest_framework_json_api/serializers.py

@@ -353,4 +353,5 @@ def to_internal_value(self, data):
                     expected_types=', '.join(expected_types), received_type=received_type))
         serializer_class = self.get_polymorphic_serializer_for_type(received_type)
         self.__class__ = serializer_class
-        return serializer_class(data, context=self.context).to_internal_value(data)
+        return serializer_class(data, context=self.context,
+                                partial=self.partial).to_internal_value(data)