Description
Checklist
- I have verified that that issue exists against the
masterbranch of Django REST framework. - I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
- This is not a usage question. (Those should be directed to the discussion group instead.)
- This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
- I have reduced the issue to the simplest possible case.
- I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)
I've a mystery here. This is the Traceback I'm getting:
Internal Server Error: {u'kwargs': {}, u'args': (), u'request': <rest_framework.request.Request object at 0x7fe51daaf8d0>, u'view': <volumes.restapi.VolumeProxyViewSet object at 0x7fe51daaf890>}
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/rest_framework/views.py", line 463, in dispatch
response = handler(request, *args, **kwargs)
File "/usr/share/openattic/rest/multinode/handlers.py", line 101, in create
return super(RequestHandlers, self).create(request, args, kwargs)
File "/usr/share/openattic/volumes/restapi.py", line 447, in create
return Response(serializer.data, status=status.HTTP_201_CREATED)
File "/usr/lib/python2.7/dist-packages/rest_framework/serializers.py", line 503, in data
ret = super(Serializer, self).data
File "/usr/lib/python2.7/dist-packages/rest_framework/serializers.py", line 239, in data
self._data = self.to_representation(self.instance)
File "/usr/share/openattic/rest/utilities.py", line 102, in to_representation
return self.to_native(instance)
File "/usr/share/openattic/volumes/restapi.py", line 331, in to_native
data.update(dict([(key, value) for (key, value) in serializer_instance.data.items()
File "/usr/lib/python2.7/dist-packages/rest_framework/serializers.py", line 503, in data
ret = super(Serializer, self).data
File "/usr/lib/python2.7/dist-packages/rest_framework/serializers.py", line 239, in data
self._data = self.to_representation(self.instance)
File "/usr/lib/python2.7/dist-packages/rest_framework/serializers.py", line 472, in to_representation
ret[field.field_name] = field.to_representation(attribute)
File "/usr/lib/python2.7/dist-packages/rest_framework/relations.py", line 355, in to_representation
raise ImproperlyConfigured(msg % self.view_name)
ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "host-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.
This is the minimal testcase:
from django.db import models
from rest_framework import viewsets, serializers, relations
class F(models.Model):
pass
class M(models.Model):
@property
def f(self):
return F.objects.get()
class FSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = F
fields = ('id', )
class MSerializer(serializers.HyperlinkedModelSerializer):
f = relations.HyperlinkedRelatedField(read_only=True, view_name='f-detail')
class Meta:
model = M
fields = ('id', 'f')
class FViewSet(viewsets.ModelViewSet):
queryset = F.objects.all()
serializer_class = FSerializer
class MViewSet(viewsets.ModelViewSet):
queryset = M.objects.all()
serializer_class = MSerializer
There is a problem, if
- You are using DRF >= 3.0
- and your serializer contains a HyperlinkedRelatedField named f
- and the corresponding model does not have a related field f.
- Instead, it has a property f returning an F-model instance, e.g.:
class M(Model):
@property
def my_prop(self):
return self.foo.my_prop
Then, the serializer will fail to generate the URL, because the HyperlinkedRelatedField
cannot cope with the fact that django.db.models.base.Model#serializable_value
returns the PK, if the model returns a field with that name, or else the model instance.
If we disable the pk-only-optimization, HyperlinkedRelatedField will not call
django.db.models.base.Model#serializable_value, thus disabling the ode path affected
by this bug.
Another idea would be to force the use of the PK for these property based
HyperlinkedRelatedFields by specifying the sorce attribute of the HyperlinkedRelatedField.
But that doesn't work, cause some serializers must support properties and ForeinKeys at
the same time.
This a regression to DRF 2, as the minimal example works there flawlessly.
Let's run manage.py shell to find out more details
Imitialize stuff (you can ignore this):
In [3]: from lvm.models import LogicalVolume
In [7]: lv = LogicalVolume.objects.get()
In [10]: from volumes.restapi import BlockVolumeSerializer
# For Mocking Request objects.
In [14]: class Yup(object):
....: def __init__(self, **kwargs):
....: self.__dict__.update(**kwargs)
....: def build_absolute_uri(self, url):
....: return 'http://localhost' + url
....:
In [19]: lvs = BlockVolumeSerializer(lv, context={'request': Yup(path='/openattic/api/volumes', GET={})})
In [10]: lvs
Out[10]:
BlockVolumeSerializer(<LogicalVolume: lv1>, context={'request': <__main__.Yup object>}):
type = ContentTypeSerializer(read_only=True, source='volume_type'):
url = HyperlinkedIdentityField(view_name='contenttype-detail')
app_label = CharField(max_length=100, required=True)
model = CharField(label='Python model class name', max_length=100, required=True)
class Meta:
validators = [<UniqueTogetherValidator(queryset=ContentType.objects.all(), fields=(u'app_label', u'model'))>]
host = HyperlinkedRelatedField(read_only=True, view_name='host-detail')
path = CharField()
perfdata = SerializerMethodField('get_performance_data')
Here is the Trachback as seen above:
In [32]: lvs.data
---------------------------------------------------------------------------
ImproperlyConfigured Traceback (most recent call last)
<ipython-input-32-e553062931ab> in <module>()
----> 1 lvs.data
/usr/lib/python2.7/dist-packages/rest_framework/serializers.pyc in data(self)
501 @property
502 def data(self):
--> 503 ret = super(Serializer, self).data
504 return ReturnDict(ret, serializer=self)
505
/usr/lib/python2.7/dist-packages/rest_framework/serializers.pyc in data(self)
237 if not hasattr(self, '_data'):
238 if self.instance is not None and not getattr(self, '_errors', None):
--> 239 self._data = self.to_representation(self.instance)
240 elif hasattr(self, '_validated_data') and not getattr(self, '_errors', None):
241 self._data = self.to_representation(self.validated_data)
/usr/lib/python2.7/dist-packages/rest_framework/serializers.pyc in to_representation(self, instance)
470 ret[field.field_name] = None
471 else:
--> 472 ret[field.field_name] = field.to_representation(attribute)
473
474 return ret
/usr/lib/python2.7/dist-packages/rest_framework/relations.pyc in to_representation(self, value)
353 "entries in your URL conf." % value_string
354 )
--> 355 raise ImproperlyConfigured(msg % self.view_name)
356
357 if url is None:
ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "host-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.
But, this works, if I call to_representation on the field directly:
In [31]: lvs.fields['host'].to_representation(lv.host)
Out[31]: u'http://localhost/api/hosts/1'
And it works, if I append 'pk' to the .sources_attrs of the field:
In [133]: lvs.fields['host'].source_attrs = [u'host', 'pk']
and it works, if I call reverse directly:
In [24]: reverse('host-detail', kwargs={'pk': lv.host.pk}, request=Yup(path='/openattic/api/volumes', GET={}))
Out[24]: u'http://localhost/api/hosts/1'
I've debuged a little bit and found PKOnlyObject().pk to be the actual object (Host), and not the primary key (e.g. 5), thus I'm guessing the root cause there.
See also our Issue: https://tracker.openattic.org/browse/OP-1676
EDIT: let's deep into the PKOnlyObject().pk issue:
In [60]: type(lvs.fields['host'].get_attribute(lv).pk)
Out[60]: ifconfig.models.Host # if this is int, it works as expected.
In [65]: lvs.fields['host'].source_attrs[:-1]
Out[65]: []
In [70]: lv.serializable_value('host')
Out[70]: <Host: oa-xen-1.oa.master.dns>
Turns out, serializable_value returns either int or Host, if the field can be found by name.
EDIT2, On my other system, to_representation actually worked with this broken PKOnlyObject().pk.
This is the output of the other system:
In [25]: reverse('host-detail', kwargs={'pk': lv.host.pk}, request=Yup(path='/openattic/api/volumes', GET={}))
Out[25]: u'http://localhost/api/hosts/1'
In [26]: reverse('host-detail', kwargs={'pk': lv.host}, request=Yup(path='/openattic/api/volumes', GET={}))
Out[26]: u'http://localhost/api/hosts/ubuntubox'
And http://localhost/api/hosts/ubuntubox is actually invalid.
EDIT3:
The error seems to be related to django.db.models.base.Model#serializable_value which returns either the related object or the primary key of the object dependent on self._meta.get_field(field_name) finding the field or not:
def serializable_value(self, field_name):
try:
field = self._meta.get_field(field_name)
except FieldDoesNotExist:
return getattr(self, field_name) # returns the Host object
return getattr(self, field.attname) # returns the Host's primary key.
Edit4:
This is our workaround: https://bitbucket.org/openattic/openattic/pull-requests/499/op-1676-workaround-for/diff