Fixes types in reverse m2m relationships (#355)

* Adds test that fails with reverse m2m relationships

* Fixes reverse m2m relationships

* Adds compatibility with Django 1.8

* Update AUTHORS

Author: Darkheir

AUTHORS

@@ -4,4 +4,5 @@ Greg Aker <[email protected]>
 Jerel Unruh <[email protected]>
 Matt Layman <http://www.mattlayman.com>
 Oliver Sauder <[email protected]>
+Raphael Cohen <[email protected]>
 Yaniv Peer <[email protected]>

example/models.py

@@ -64,7 +64,7 @@ class Entry(BaseModel):
     body_text = models.TextField(null=True)
     pub_date = models.DateField(null=True)
     mod_date = models.DateField(null=True)
-    authors = models.ManyToManyField(Author)
+    authors = models.ManyToManyField(Author, related_name='entries')
     n_comments = models.IntegerField(default=0)
     n_pingbacks = models.IntegerField(default=0)
     rating = models.IntegerField(default=0)

example/serializers.py

@@ -92,7 +92,7 @@ class AuthorBioSerializer(serializers.ModelSerializer):
 
     class Meta:
         model = AuthorBio
-        fields = ('author', 'body',)
+        fields = ('author', 'body')
 
 
 class AuthorSerializer(serializers.ModelSerializer):
@@ -102,7 +102,7 @@ class AuthorSerializer(serializers.ModelSerializer):
 
     class Meta:
         model = Author
-        fields = ('name', 'email', 'bio')
+        fields = ('name', 'email', 'bio', 'entries')
 
 
 class CommentSerializer(serializers.ModelSerializer):

example/tests/test_utils.py

@@ -3,7 +3,7 @@
 """
 from rest_framework_json_api import utils
 
-from ..serializers import EntrySerializer
+from ..serializers import EntrySerializer, AuthorSerializer
 from ..tests import TestBase
 
 
@@ -29,3 +29,12 @@ def test_m2m_relation(self):
         field = serializer.fields['authors']
 
         self.assertEqual(utils.get_related_resource_type(field), 'authors')
+
+    def test_m2m_reverse_relation(self):
+        """
+        Ensure reverse m2ms have their types identified correctly.
+        """
+        serializer = AuthorSerializer()
+        field = serializer.fields['entries']
+
+        self.assertEqual(utils.get_related_resource_type(field), 'entries')

rest_framework_json_api/utils.py

@@ -237,7 +237,16 @@ def get_related_resource_type(relation):
                 else:
                     relation_model = parent_model_relation.related.model
             elif parent_model_relation_type is ManyToManyDescriptor:
-                relation_model = parent_model_relation.field.remote_field.model
+                if django.VERSION >= (1, 9):
+                    relation_model = parent_model_relation.field.remote_field.model
+                    # In case we are in a reverse relation
+                    if relation_model == parent_model:
+                        relation_model = parent_model_relation.field.model
+                elif django.VERSION >= (1, 8):
+                    relation_model = parent_model_relation.related.model
+                    # In case we are in a reverse relation
+                    if relation_model == parent_model:
+                        relation_model = parent_model_relation.related.related_model
             elif parent_model_relation_type is ReverseManyRelatedObjectsDescriptor:
                 relation_model = parent_model_relation.field.related.model
             elif parent_model_relation_type is ReverseGenericManyToOneDescriptor: