Browsable api raises AttributeError when posting raw data not containing data for nested serializer

[jgadelange]

When I post an empty object ({}) using the raw data form in the browsable API I get an AttributeError, when I have a nested serializer defined on the serializer set for that view. Example code and stack trace can be found below.

Example code:

class NestedSerializer(serializers.Serializer):
    sub_field = serializers.CharField()


class MainSerializer(serializers.Serializer):
    nested = NestedSerializer()


class TestView(APIView):
    serializer_class = MainSerializer

    def get_serializer(self, **kwargs):
        return self.serializer_class(**kwargs)

    def post(self, request, format=None):
        serializer = self.get_serializer(data=request.data)
        if serializer.is_valid():
            serializer.create(serializer.validated_data)
            return Response(serializer.data, status=status.HTTP_200_OK)

        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Traceback (most recent call last):
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/core/handlers/base.py", line 164, in get_response
    response = response.render()
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/response.py", line 158, in render
    self.content = self.rendered_content
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/response.py", line 60, in rendered_content
    ret = renderer.render(self.data, media_type, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 669, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 646, in get_context
    'post_form': self.get_rendered_html_form(data, view, 'POST', request),
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 513, in get_rendered_html_form
    [('template', 'rest_framework/api_form.html')]
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 367, in render
    return template.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/backends/django.py", line 74, in render
    return self.template.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 209, in render
    return self._render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
    return self.nodelist.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 903, in render
    bit = self.render_node(node, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/debug.py", line 79, in render_node
    return node.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/defaulttags.py", line 217, in render
    nodelist.append(node.render(context))
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/defaulttags.py", line 329, in render
    return nodelist.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 903, in render
    bit = self.render_node(node, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/debug.py", line 79, in render_node
    return node.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 1195, in render
    return func(*resolved_args, **resolved_kwargs)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/templatetags/rest_framework.py", line 31, in render_field
    return renderer.render_field(field, style)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 325, in render_field
    field = field.as_form_field()
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/utils/serializer_helpers.py", line 99, in as_form_field
    for key, value in self.value.items():
AttributeError: 'NoneType' object has no attribute 'items'

[tomchristie]

Okay, believe this is now resolved in master, to be released as 3.2.2 either today or later this week.

Desperately need some good tests around all this but this quick fix will need to do for now.

[jgadelange]

I was just working on a pull request for this myself. I was planning to add the following code to NestedBoundField:

def __init__(self, field, value, errors, prefix=''):
        if value is None:
            value = {}
        super(NestedBoundField, self).__init__(field, value, errors, prefix)

I believe the current fix is not correct, since it will also "remove" the form for the nested serializer all together:

[tomchristie]

@jgadelange Gotcha - best thing would probably be to go ahead with that pull request then.

[jgadelange]

Hmmmm... when testing this some more I found an other error. When leaving out a required field the errors on the 'NestedBoundedField' is a list ([u'This field is required.']). I will look into this more tomorrow.

Traceback (most recent call last):
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/core/handlers/base.py", line 164, in get_response
    response = response.render()
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/response.py", line 158, in render
    self.content = self.rendered_content
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/response.py", line 71, in rendered_content
    ret = renderer.render(self.data, media_type, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 669, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 646, in get_context
    'post_form': self.get_rendered_html_form(data, view, 'POST', request),
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 513, in get_rendered_html_form
    [('template', 'rest_framework/api_form.html')]
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 367, in render
    return template.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/backends/django.py", line 74, in render
    return self.template.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 209, in render
    return self._render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
    return self.nodelist.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 903, in render
    bit = self.render_node(node, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/debug.py", line 79, in render_node
    return node.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/defaulttags.py", line 217, in render
    nodelist.append(node.render(context))
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/defaulttags.py", line 329, in render
    return nodelist.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 903, in render
    bit = self.render_node(node, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/debug.py", line 79, in render_node
    return node.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 1195, in render
    return func(*resolved_args, **resolved_kwargs)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/templatetags/rest_framework.py", line 31, in render_field
    return renderer.render_field(field, style)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/renderers.py", line 337, in render_field
    return template.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/backends/django.py", line 74, in render
    return self.template.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 209, in render
    return self._render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 201, in _render
    return self.nodelist.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/base.py", line 903, in render
    bit = self.render_node(node, context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/debug.py", line 79, in render_node
    return node.render(context)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/django/template/defaulttags.py", line 161, in render
    values = list(values)
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/utils/serializer_helpers.py", line 98, in __iter__
    yield self[field.field_name]
  File "<path_to_virtualenv>/lib/python2.7/site-packages/rest_framework/utils/serializer_helpers.py", line 103, in __getitem__
    error = self.errors.get(key) if self.errors else None
AttributeError: 'list' object has no attribute 'get'

[cancan101]

I seeing this in v3.5.3:

AttributeError: 'list' object has no attribute 'get'
  File "django/core/handlers/exception.py", line 39, in inner
    response = get_response(request)
  File "django/core/handlers/base.py", line 249, in _legacy_get_response
    response = self._get_response(request)
  File "django/core/handlers/base.py", line 217, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "django/core/handlers/base.py", line 215, in _get_response
    response = response.render()
  File "django/template/response.py", line 109, in render
    self.content = self.rendered_content
  File "rest_framework/response.py", line 72, in rendered_content
    ret = renderer.render(self.data, accepted_media_type, context)
  File "rest_framework/renderers.py", line 701, in render
    context = self.get_context(data, accepted_media_type, renderer_context)
  File "rest_framework/renderers.py", line 673, in get_context
    'put_form': self.get_rendered_html_form(data, view, 'PUT', request),
  File "rest_framework/renderers.py", line 489, in get_rendered_html_form
    return self.render_form_for_serializer(existing_serializer)
  File "rest_framework/renderers.py", line 517, in render_form_for_serializer
    {'style': {'template_pack': 'rest_framework/horizontal'}}
  File "rest_framework/renderers.py", line 369, in render
    return template_render(template, context)
  File "rest_framework/compat.py", line 306, in template_render
    return template.render(context, request=request)
  File "django/template/backends/django.py", line 66, in render
    return self.template.render(context)
  File "django/template/base.py", line 208, in render
    return self._render(context)
  File "newrelic/api/function_trace.py", line 98, in dynamic_wrapper
    return wrapped(*args, **kwargs)
  File "django/template/base.py", line 199, in _render
    return self.nodelist.render(context)
  File "django/template/base.py", line 994, in render
    bit = node.render_annotated(context)
  File "django/template/base.py", line 961, in render_annotated
    return self.render(context)
  File "django/template/defaulttags.py", line 209, in render
    nodelist.append(node.render_annotated(context))
  File "django/template/base.py", line 961, in render_annotated
    return self.render(context)
  File "django/template/defaulttags.py", line 315, in render
    return nodelist.render(context)
  File "django/template/base.py", line 994, in render
    bit = node.render_annotated(context)
  File "django/template/base.py", line 961, in render_annotated
    return self.render(context)
  File "django/template/library.py", line 203, in render
    output = self.func(*resolved_args, **resolved_kwargs)
  File "rest_framework/templatetags/rest_framework.py", line 37, in render_field
    return renderer.render_field(field, style)
  File "rest_framework/renderers.py", line 348, in render_field
    return template_render(template, context)
  File "rest_framework/compat.py", line 306, in template_render
    return template.render(context, request=request)
  File "django/template/backends/django.py", line 66, in render
    return self.template.render(context)
  File "django/template/base.py", line 208, in render
    return self._render(context)
  File "newrelic/api/function_trace.py", line 98, in dynamic_wrapper
    return wrapped(*args, **kwargs)
  File "django/template/base.py", line 199, in _render
    return self.nodelist.render(context)
  File "django/template/base.py", line 994, in render
    bit = node.render_annotated(context)
  File "django/template/base.py", line 961, in render_annotated
    return self.render(context)
  File "django/template/defaulttags.py", line 165, in render
    values = list(values)
  File "rest_framework/utils/serializer_helpers.py", line 99, in __iter__
    yield self[field.field_name]
  File "rest_framework/utils/serializer_helpers.py", line 104, in __getitem__
    error = self.errors.get(key) if self.errors else None

And this is self:
<NestedBoundField value={} errors=[u'This field is required.']>

[cancan101]

@tomchristie I think this issue still exists as the description above also matches my scenario.

[tomchristie]

Able to replicate it in a super slimmed-down example case?

[cancan101]

@tomchristie https://www.dropbox.com/s/vm6denvw9depy5s/mysite.zip?dl=0
Using browsable API to POST to /person/ a payload of {}:

[aruseni]

I can still reproduce it in 3.5.4.

Models:

class NoteDescription(models.Model):
    color = models.CharField(max_length=100)


class Note(models.Model):
    content = models.CharField(max_length=100)
    description = models.ForeignKey(NoteDescription, on_delete=models.CASCADE)

Serializers:

class NoteDescriptionSerializer(serializers.ModelSerializer):
    class Meta:
        model = NoteDescription
        fields = ("color",)


class NoteSerializer(serializers.ModelSerializer):
    description = NoteDescriptionSerializer()

    class Meta:
        model = Note
        fields = ("content", "description")

A simple viewset to try it:

class NoteViewSet(viewsets.GenericViewSet):
    serializer_class = NoteSerializer

    def create(self, request):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        return Response(serializer.data)

Then you just need to make a POST request only containing {} with Browsable.

[xordoquy]

Tested on one of my project with latest released DRF and got a correct response:

HTTP 400 Bad Request
Allow: GET, POST, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "lanes": [
        "This field is required."
    ],
    "name": [
        "This field is required."
    ]
}