From 76e039d70e8fc7f1d5c65180cb544abab81e600e Mon Sep 17 00:00:00 2001
From: Tom Christie <tom@tomchristie.com>
Date: Wed, 10 Apr 2013 22:38:02 +0100
Subject: [PATCH] First pass on automatically including reverse relationship

---
 rest_framework/serializers.py      | 43 +++++++++++++++++++++++++-----
 rest_framework/tests/serializer.py | 37 +++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 6 deletions(-)

diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index e28bbe81d..eac909c7b 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -598,6 +598,24 @@ class ModelSerializer(Serializer):
             if field:
                 ret[model_field.name] = field
 
+        # Reverse relationships are only included if they are explicitly
+        # present in `Meta.fields`.
+        if self.opts.fields:
+            reverse = opts.get_all_related_objects()
+            reverse += opts.get_all_related_many_to_many_objects()
+            for rel in reverse:
+                name = rel.get_accessor_name()
+                if name not in self.opts.fields:
+                    continue
+
+                if nested:
+                    field = self.get_nested_field(None, rel)
+                else:
+                    field = self.get_related_field(None, rel, to_many=True)
+
+                if field:
+                    ret[name] = field
+
         for field_name in self.opts.read_only_fields:
             assert field_name in ret, \
                 "read_only_fields on '%s' included invalid item '%s'" % \
@@ -612,24 +630,36 @@ class ModelSerializer(Serializer):
         """
         return self.get_field(model_field)
 
-    def get_nested_field(self, model_field):
+    def get_nested_field(self, model_field, rel=None):
         """
         Creates a default instance of a nested relational field.
         """
+        if rel:
+            model_class = rel.model
+        else:
+            model_class = model_field.rel.to
+
         class NestedModelSerializer(ModelSerializer):
             class Meta:
-                model = model_field.rel.to
+                model = model_class
         return NestedModelSerializer()
 
-    def get_related_field(self, model_field, to_many=False):
+    def get_related_field(self, model_field, rel=None, to_many=False):
         """
         Creates a default instance of a flat relational field.
         """
         # TODO: filter queryset using:
         # .using(db).complex_filter(self.rel.limit_choices_to)
+        if rel:
+            model_class = rel.model
+            required = True
+        else:
+            model_class = model_field.rel.to
+            required = not(model_field.null or model_field.blank)
+
         kwargs = {
-            'required': not(model_field.null or model_field.blank),
-            'queryset': model_field.rel.to._default_manager,
+            'required': required,
+            'queryset': model_class._default_manager,
             'many': to_many
         }
 
@@ -797,7 +827,8 @@ class HyperlinkedModelSerializer(ModelSerializer):
         return self._default_view_name % format_kwargs
 
     def get_pk_field(self, model_field):
-        return None
+        if self.opts.fields and model_field.name in self.opts.fields:
+            return self.get_field(model_field)
 
     def get_related_field(self, model_field, to_many):
         """
diff --git a/rest_framework/tests/serializer.py b/rest_framework/tests/serializer.py
index 05217f35a..3a94fad5d 100644
--- a/rest_framework/tests/serializer.py
+++ b/rest_framework/tests/serializer.py
@@ -738,6 +738,43 @@ class ManyRelatedTests(TestCase):
 
         self.assertEqual(serializer.data, expected)
 
+    def test_include_reverse_relations(self):
+        post = BlogPost.objects.create(title="Test blog post")
+        post.blogpostcomment_set.create(text="I hate this blog post")
+        post.blogpostcomment_set.create(text="I love this blog post")
+
+        class BlogPostSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = BlogPost
+                fields = ('id', 'title', 'blogpostcomment_set')
+
+        serializer = BlogPostSerializer(instance=post)
+        expected = {
+            'id': 1, 'title': 'Test blog post', 'blogpostcomment_set': [1, 2]
+        }
+        self.assertEqual(serializer.data, expected)
+
+    def test_depth_include_reverse_relations(self):
+        post = BlogPost.objects.create(title="Test blog post")
+        post.blogpostcomment_set.create(text="I hate this blog post")
+        post.blogpostcomment_set.create(text="I love this blog post")
+
+        class BlogPostSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = BlogPost
+                fields = ('id', 'title', 'blogpostcomment_set')
+                depth = 1
+
+        serializer = BlogPostSerializer(instance=post)
+        expected = {
+            'id': 1, 'title': 'Test blog post',
+            'blogpostcomment_set': [
+                {'id': 1, 'text': 'I hate this blog post', 'blog_post': 1},
+                {'id': 2, 'text': 'I love this blog post', 'blog_post': 1}
+            ]
+        }
+        self.assertEqual(serializer.data, expected)
+
     def test_callable_source(self):
         post = BlogPost.objects.create(title="Test blog post")
         post.blogpostcomment_set.create(text="I love this blog post")