Allow relative style hyperlinked URLs

docs/api-guide/serializers.md

@@ -678,6 +678,25 @@ You can explicitly include the primary key by adding it to the `fields` option,
             model = Account
             fields = ('url', 'id', 'account_name', 'users', 'created')
 
+## Absolute and relative URLs
+
+When instantiating a `HyperlinkedModelSerializer` you must include the current
+`request` in the serializer context, for example:
+
+    serializer = AccountSerializer(queryset, context={'request': request})
+
+Doing so will ensure that the hyperlinks can include an appropriate hostname,
+so that the resulting representation uses fully qualified URLs, such as:
+
+    http://api.example.com/accounts/1/
+
+Rather than relative URLs, such as:
+
+    /accounts/1/
+
+If you *do* want to use relative URLs, you should explicitly pass `{'request': None}`
+in the serializer context.
+
 ## How hyperlinked views are determined
 
 There needs to be a way of determining which views should be used for hyperlinking to model instances.

rest_framework/relations.py

@@ -325,15 +325,15 @@ class HyperlinkedRelatedField(RelatedField):
             self.fail('does_not_exist')
 
     def to_representation(self, value):
-        request = self.context.get('request', None)
-        format = self.context.get('format', None)
-
-        assert request is not None, (
+        assert 'request' in self.context, (
             "`%s` requires the request in the serializer"
             " context. Add `context={'request': request}` when instantiating "
             "the serializer." % self.__class__.__name__
         )
 
+        request = self.context['request']
+        format = self.context.get('format', None)
+
         # By default use whatever format is given for the current context
         # unless the target is a different type to the source.
         #

tests/test_relations_hyperlink.py

@@ -82,6 +82,17 @@ class HyperlinkedManyToManyTests(TestCase):
             for target in ManyToManyTarget.objects.all():
                 source.targets.add(target)
 
+    def test_relative_hyperlinks(self):
+        queryset = ManyToManySource.objects.all()
+        serializer = ManyToManySourceSerializer(queryset, many=True, context={'request': None})
+        expected = [
+            {'url': '/manytomanysource/1/', 'name': 'source-1', 'targets': ['/manytomanytarget/1/']},
+            {'url': '/manytomanysource/2/', 'name': 'source-2', 'targets': ['/manytomanytarget/1/', '/manytomanytarget/2/']},
+            {'url': '/manytomanysource/3/', 'name': 'source-3', 'targets': ['/manytomanytarget/1/', '/manytomanytarget/2/', '/manytomanytarget/3/']}
+        ]
+        with self.assertNumQueries(4):
+            self.assertEqual(serializer.data, expected)
+
     def test_many_to_many_retrieve(self):
         queryset = ManyToManySource.objects.all()
         serializer = ManyToManySourceSerializer(queryset, many=True, context={'request': request})