From 4e561a4ac02afe1f4883ba3347a422c876da1e91 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89tienne=20Beaul=C3=A9?= <beauleetienne0@gmail.com>
Date: Thu, 5 Mar 2020 20:13:15 -0500
Subject: [PATCH] Allow serializer data to include related objects by object

When instantiating a serializer from cleaned data, the relational fields
have been already converted into objects, which makes the fields
invalid. Having a valid object as the value of a field is not
necessarily considered valid, if the object is not in the given
queryset.

As such, this change adds a check to allow objects of the model type and
in the queryset in lieu of the proper representation.
---
 rest_framework/relations.py | 10 +++++++++-
 tests/test_relations.py     | 13 +++++++++++++
 tests/test_versioning.py    |  5 +++++
 tests/utils.py              |  2 ++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/rest_framework/relations.py b/rest_framework/relations.py
index 3a2a8fb4b..06e886efd 100644
--- a/rest_framework/relations.py
+++ b/rest_framework/relations.py
@@ -250,7 +250,9 @@ class PrimaryKeyRelatedField(RelatedField):
         return True
 
     def to_internal_value(self, data):
-        if self.pk_field is not None:
+        if isinstance(data, self.get_queryset().model):
+            data = data.pk
+        elif self.pk_field is not None:
             data = self.pk_field.to_internal_value(data)
         try:
             return self.get_queryset().get(pk=data)
@@ -331,6 +333,12 @@ class HyperlinkedRelatedField(RelatedField):
         return self.reverse(view_name, kwargs=kwargs, request=request, format=format)
 
     def to_internal_value(self, data):
+        if isinstance(data, self.get_queryset().model):
+            try:
+                return self.get_queryset().get(**{self.lookup_url_kwarg: getattr(data, self.lookup_field)})
+            except (ObjectDoesNotExist, ObjectValueError, ObjectTypeError):
+                self.fail('does_not_exist')
+
         request = self.context.get('request', None)
         try:
             http_prefix = data.startswith(('http:', 'https:'))
diff --git a/tests/test_relations.py b/tests/test_relations.py
index 9f05e3b31..e53182a2a 100644
--- a/tests/test_relations.py
+++ b/tests/test_relations.py
@@ -116,6 +116,10 @@ class TestPrimaryKeyRelatedField(APISimpleTestCase):
         instance = field.to_internal_value(self.instance.pk)
         assert instance is self.instance
 
+    def test_pk_related_object_given(self):
+        instance = self.field.to_internal_value(self.instance)
+        assert instance is self.queryset.items[2]
+
 
 class TestProxiedPrimaryKeyRelatedField(APISimpleTestCase):
     def setUp(self):
@@ -216,6 +220,11 @@ class TestHyperlinkedRelatedField(APISimpleTestCase):
 
     def hyperlinked_related_queryset_error(self, exc_type):
         class QuerySet:
+            class FakeObject:
+                pass
+
+            model = FakeObject
+
             def get(self, *args, **kwargs):
                 raise exc_type
 
@@ -235,6 +244,10 @@ class TestHyperlinkedRelatedField(APISimpleTestCase):
     def test_hyperlinked_related_queryset_value_error(self):
         self.hyperlinked_related_queryset_error(ValueError)
 
+    def test_hyperlinked_related_object_given(self):
+        instance = self.field.to_internal_value(self.queryset.items[2])
+        assert instance is self.queryset.items[2]
+
 
 class TestHyperlinkedIdentityField(APISimpleTestCase):
     def setUp(self):
diff --git a/tests/test_versioning.py b/tests/test_versioning.py
index d4e269df3..a0efd8fc2 100644
--- a/tests/test_versioning.py
+++ b/tests/test_versioning.py
@@ -322,6 +322,11 @@ class TestHyperlinkedRelatedField(URLPatternsTestCase, APITestCase):
         super().setUp()
 
         class MockQueryset:
+            class MockObject:
+                pass
+
+            model = MockObject
+
             def get(self, pk):
                 return 'object %s' % pk
 
diff --git a/tests/utils.py b/tests/utils.py
index 06e5b9abe..2d31976f1 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -17,6 +17,8 @@ class MockObject:
 
 
 class MockQueryset:
+    model = MockObject
+
     def __init__(self, iterable):
         self.items = iterable