From 923f81d26971510c12cb08e3061c7b37c0c6ffe8 Mon Sep 17 00:00:00 2001
From: Tom Christie
Date: Sat, 29 Dec 2012 13:19:05 +0000
Subject: Nested serializers now support nullable relationships, plus test. 
 Fixes #384

---
 docs/topics/release-notes.md             |  4 ++++
 rest_framework/serializers.py            |  3 +++
 rest_framework/tests/relations_nested.py | 35 ++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/docs/topics/release-notes.md b/docs/topics/release-notes.md
index 0a17f1a6..dd54a613 100644
--- a/docs/topics/release-notes.md
+++ b/docs/topics/release-notes.md
@@ -16,6 +16,10 @@ Major version numbers (x.0.0) are reserved for project milestones.  No major poi
 
 ## 2.1.x series
 
+### Master
+
+* Bugfix: Nested serializers now support nullable relationships.
+
 ### 2.1.13
 
 **Date**: 28th Dec 2012
diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 8156bc18..d8350f95 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -307,6 +307,9 @@ class BaseSerializer(Field):
         if is_simple_callable(getattr(obj, 'all', None)):
             return [self.to_native(item) for item in obj.all()]
 
+        if obj is None:
+            return None
+
         return self.to_native(obj)
 
     @property
diff --git a/rest_framework/tests/relations_nested.py b/rest_framework/tests/relations_nested.py
index 297538c4..b1147378 100644
--- a/rest_framework/tests/relations_nested.py
+++ b/rest_framework/tests/relations_nested.py
@@ -32,6 +32,20 @@ class ForeignKeyTargetSerializer(serializers.ModelSerializer):
         model = ForeignKeyTarget
 
 
+# Nullable ForeignKey
+
+class NullableForeignKeySource(models.Model):
+    name = models.CharField(max_length=100)
+    target = models.ForeignKey(ForeignKeyTarget, null=True, blank=True,
+                               related_name='nullable_sources')
+
+
+class NullableForeignKeySourceSerializer(serializers.ModelSerializer):
+    class Meta:
+        depth = 1
+        model = NullableForeignKeySource
+
+
 class ReverseForeignKeyTests(TestCase):
     def setUp(self):
         target = ForeignKeyTarget(name='target-1')
@@ -65,3 +79,24 @@ class ReverseForeignKeyTests(TestCase):
             ]}
         ]
         self.assertEquals(serializer.data, expected)
+
+
+class NestedNullableForeignKeyTests(TestCase):
+    def setUp(self):
+        target = ForeignKeyTarget(name='target-1')
+        target.save()
+        for idx in range(1, 4):
+            if idx == 3:
+                target = None
+            source = NullableForeignKeySource(name='source-%d' % idx, target=target)
+            source.save()
+
+    def test_foreign_key_retrieve_with_null(self):
+        queryset = NullableForeignKeySource.objects.all()
+        serializer = NullableForeignKeySourceSerializer(queryset)
+        expected = [
+            {'id': 1, 'name': u'source-1', 'target': {'id': 1, 'name': u'target-1'}},
+            {'id': 2, 'name': u'source-2', 'target': {'id': 1, 'name': u'target-1'}},
+            {'id': 3, 'name': u'source-3', 'target': None},
+        ]
+        self.assertEquals(serializer.data, expected)
-- 
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