Fix Serializer.data when provided invalid 'data' (#5646)

* Test serializer/API renderer for invalid datatype

* Fix Serializer.data with invalid input datatype

rest_framework/serializers.py

@@ -398,6 +398,10 @@ class Serializer(BaseSerializer):
 
     def get_initial(self):
         if hasattr(self, 'initial_data'):
+            # initial_data may not be a valid type
+            if not isinstance(self.initial_data, Mapping):
+                return OrderedDict()
+
             return OrderedDict([
                 (field_name, field.get_value(self.initial_data))
                 for field_name, field in self.fields.items()

tests/browsable_api/test_form_rendering.py

@@ -14,6 +14,10 @@ class BasicSerializer(serializers.ModelSerializer):
         fields = '__all__'
 
 
+class StandardPostView(generics.CreateAPIView):
+    serializer_class = BasicSerializer
+
+
 class ManyPostView(generics.GenericAPIView):
     queryset = BasicModel.objects.all()
     serializer_class = BasicSerializer
@@ -24,6 +28,32 @@ class ManyPostView(generics.GenericAPIView):
         return Response(serializer.data, status.HTTP_200_OK)
 
 
+class TestPostingListData(TestCase):
+    """
+    POSTing a list of data to a regular view should not cause the browsable
+    API to fail during rendering.
+
+    Regression test for https://github.com/encode/django-rest-framework/issues/5637
+    """
+
+    def test_json_response(self):
+        # sanity check for non-browsable API responses
+        view = StandardPostView.as_view()
+        request = factory.post('/', [{}], format='json')
+        response = view(request).render()
+
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertTrue('non_field_errors' in response.data)
+
+    def test_browsable_api(self):
+        view = StandardPostView.as_view()
+        request = factory.post('/?format=api', [{}], format='json')
+        response = view(request).render()
+
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertTrue('non_field_errors' in response.data)
+
+
 class TestManyPostView(TestCase):
     def setUp(self):
         """

tests/test_serializer.py

@@ -77,14 +77,23 @@ class TestSerializer:
         serializer = self.Serializer(data={'char': 'abc', 'integer': 123})
         assert serializer.is_valid()
         assert serializer.validated_data == {'char': 'abc', 'integer': 123}
+        assert serializer.data == {'char': 'abc', 'integer': 123}
         assert serializer.errors == {}
 
     def test_invalid_serializer(self):
         serializer = self.Serializer(data={'char': 'abc'})
         assert not serializer.is_valid()
         assert serializer.validated_data == {}
+        assert serializer.data == {'char': 'abc'}
         assert serializer.errors == {'integer': ['This field is required.']}
 
+    def test_invalid_datatype(self):
+        serializer = self.Serializer(data=[{'char': 'abc'}])
+        assert not serializer.is_valid()
+        assert serializer.validated_data == {}
+        assert serializer.data == {}
+        assert serializer.errors == {'non_field_errors': ['Invalid data. Expected a dictionary, but got list.']}
+
     def test_partial_validation(self):
         serializer = self.Serializer(data={'char': 'abc'}, partial=True)
         assert serializer.is_valid()