Merge 0705671731 into 8bd5e7e612

docs/api-guide/relations.md

@@ -308,7 +308,7 @@ See the Django documentation on [reverse relationships][reverse-relationships] f
 
 ## Generic relationships
 
-If you want to serialize a generic foreign key, you need to define a custom field, to determine explicitly how you want serialize the targets of the relationship.
+If you want to serialize a generic foreign key, you need to define a `GenericRelatedField` with a configuration dictionary as first argument, that describes the representation of each model you possibly want to connect to the generic foreign key.
 
 For example, given the following model for a tag, which has a generic relationship with other arbitrary models:
 
@@ -343,40 +343,112 @@ And the following two models, which may be have associated tags:
         text = models.CharField(max_length=1000)
         tags = GenericRelation(TaggedItem)
 
-We could define a custom field that could be used to serialize tagged instances, using the type of each instance to determine how it should be serialized.
+Now we define serializers for each model that may get associated with tags.
 
-    class TaggedObjectRelatedField(serializers.RelatedField):
+    class BookmarkSerializer(serializers.ModelSerializer):
         """
-        A custom field to use for the `tagged_object` generic relationship.
+        A simple `ModelSerializer` subclass for serializing `Bookmark` objects.
         """
+        class Meta:
+            model = Bookmark
+            exclude = ('id', )
 
-        def to_native(self, value):
+
+    class NoteSerializer(serializers.ModelSerializer):
+        """
+        A simple `ModelSerializer` subclass for serializing `Note` objects.
+        """
+        class Meta:
+            model = Note
+            exclude = ('id', )
+
+The model serializer for the `Tag` model could look like this:
+
+    class TagSerializer(serializers.ModelSerializer):
+        """
+        A `Tag` serializer with a `GenericRelatedField` mapping all possible
+        models to their respective serializers.
+        """
+        tagged_object = serializers.GenericRelatedField({
+            Bookmark: BookmarkSerializer(),
+            Note: NoteSerializer()
+        }, read_only=True)
+
+        class Meta:
+            model = Tag
+            exclude = ('id', )
+
+The JSON representation of a `Tag` object with `name='django'` and its generic foreign key pointing at a `Bookmark` object with `url='https://www.djangoproject.com/'` would look like this:
+
+    {
+        'tagged_object': {
+            'url': 'https://www.djangoproject.com/'
+        },
+        'tag_name': 'django'
+    }
+
+If you want to have your generic foreign key represented as hyperlink, simply use `HyperlinkedRelatedField` objects:
+
+    class TagSerializer(serializers.ModelSerializer):
+        """
+        A `Tag` serializer with a `GenericRelatedField` mapping all possible
+        models to properly set up `HyperlinkedRelatedField`s.
+        """
+        tagged_object = serializers.GenericRelatedField({
+            Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+            Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+        }, read_only=True)
+
+        class Meta:
+            model = Tag
+            exclude = ('id', )
+
+The JSON representation of the same `Tag` example object could now look something like this:
+
+    {
+        'tagged_object': '/bookmark/1/',
+        'tag_name': 'django'
+    }
+
+These examples cover the default behavior of generic foreign key representation. However, you may also want to write to generic foreign key fields through your API.
+
+By default, a `GenericRelatedField` iterates over its nested serializers and returns the value of the first serializer, that is actually able to perform `from_native`` on the input value without any errors.
+Note, that (at the moment) only `HyperlinkedRelatedField` is able to serialize model objects out of the box.
+
+This `Tag` serializer is able to write to it's generic foreign key field:
+
+    class TagSerializer(serializers.ModelSerializer):
             """
-            Serialize tagged objects to a simple textual representation.
-            """                            
-            if isinstance(value, Bookmark):
-                return 'Bookmark: ' + value.url
-            elif isinstance(value, Note):
-                return 'Note: ' + value.text
-            raise Exception('Unexpected type of tagged object')
-
-If you need the target of the relationship to have a nested representation, you can  use the required serializers inside the `.to_native()` method:
-
-        def to_native(self, value):
+            A `Tag` serializer with a `GenericRelatedField` mapping all possible
+            models to properly set up `HyperlinkedRelatedField`s.
             """
-            Serialize bookmark instances using a bookmark serializer,
-            and note instances using a note serializer.
-            """                            
-            if isinstance(value, Bookmark):
-                serializer = BookmarkSerializer(value)
-            elif isinstance(value, Note):
-                serializer = NoteSerializer(value)
-            else:
-                raise Exception('Unexpected type of tagged object')
+            tagged_object = serializers.GenericRelatedField({
+                Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+                Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+            }, read_only=False)
 
-            return serializer.data
+            class Meta:
+                model = Tag
+                exclude = ('id', )
 
-Note that reverse generic keys, expressed using the `GenericRelation` field, can be serialized using the regular relational field types, since the type of the target in the relationship is always known.
+The following operations would create a `Tag` object with it's `tagged_object` property pointing at the `Bookmark` object found at the given detail end point.
+
+    tag_serializer = TagSerializer(data={
+        'tag_name': 'python'
+        'tagged_object': '/bookmark/1/'
+    })
+
+    tag_serializer.is_valid()
+    tag_serializer.save()
+
+If you feel that this default behavior doesn't suit your needs, you can subclass `GenericRelatedField` and override its `determine_deserializer_for_data` or `determine_serializer_for_data` respectively to implement your own way of decision-making.
+
+A few things you should note:
+
+* Although `GenericForeignKey` fields can be set to any model object, the `GenericRelatedField` only handles models explicitly defined in its configuration dictionary.
+* Reverse generic keys, expressed using the `GenericRelation` field, can be serialized using the regular relational field types, since the type of the target in the relationship is always known.
+* Please take into account that the order in which you register serializers matters as far as write operations are concerned.
+* Unless you provide custom serializer determination, only `HyperlinkedRelatedFields` provide write access to generic model relations.
 
 For more information see [the Django documentation on generic relations][generic-relations].
 

rest_framework/genericrelations.py

@@ -0,0 +1,87 @@
+from __future__ import unicode_literals
+
+from django.core.exceptions import ValidationError
+from django.utils.translation import ugettext_lazy as _
+from django import forms
+
+from rest_framework import six
+from rest_framework import serializers
+from rest_framework.exceptions import ConfigurationError
+
+
+class GenericRelatedField(serializers.WritableField):
+    """
+    Represents a generic relation foreign key.
+    It's actually more of a wrapper, that delegates the logic to registered serializers based on the `Model` class.
+    """
+    default_error_messages = {
+        'no_model_match': _('Invalid model - model not available.'),
+        'no_url_match': _('Invalid hyperlink - No URL match'),
+        'incorrect_url_match': _('Invalid hyperlink - view name not available'),
+    }
+
+    form_field_class = forms.URLField
+
+    def __init__(self, serializers, *args, **kwargs):
+        """
+        Needs an extra parameter `serializers` which has to be a dict key: value being `Model`: serializer.
+        """
+        super(GenericRelatedField, self).__init__(*args, **kwargs)
+        self.serializers = serializers
+        for model, serializer in six.iteritems(self.serializers):
+            # We have to do it, because the serializer can't access a explicit manager through the
+            # GenericForeignKey field on the model.
+            if hasattr(serializer, 'queryset') and serializer.queryset is None:
+                serializer.queryset = model._default_manager.all()
+
+    def field_to_native(self, obj, field_name):
+        """
+        Delegates to the `to_native` method of the serializer registered under obj.__class__
+        """
+        value = super(GenericRelatedField, self).field_to_native(obj, field_name)
+        serializer = self.determine_deserializer_for_data(value)
+
+        # Necessary because of context, field resolving etc.
+        serializer.initialize(self.parent, field_name)
+        return serializer.to_native(value)
+
+    def to_native(self, value):
+        # Override to prevent the simplifying process of value as present in `WritableField.to_native`.
+        return value
+
+    def from_native(self, value):
+        # Get the serializer responsible for input resolving
+        try:
+            serializer = self.determine_serializer_for_data(value)
+        except ConfigurationError as e:
+            raise ValidationError(e)
+        serializer.initialize(self.parent, self.source)
+        return serializer.from_native(value)
+
+    def determine_deserializer_for_data(self, value):
+        try:
+            model = value.__class__
+            serializer = self.serializers[model]
+        except KeyError:
+            raise ValidationError(self.error_messages['no_model_match'])
+        return serializer
+
+    def determine_serializer_for_data(self, value):
+        # While one could easily execute the "try" block within from_native and reduce operations, I consider  the
+        # concept of serializing is already very naive and vague, that's why I'd go for stringency with the deserialization
+        # process here.
+        serializers = []
+        for serializer in six.itervalues(self.serializers):
+            try:
+                serializer.from_native(value)
+                # Collects all serializers that can handle the input data.
+                serializers.append(serializer)
+            except:
+                pass
+        # If no serializer found, raise error.
+        l = len(serializers)
+        if l < 1:
+            raise ConfigurationError('Could not determine a valid serializer for value %r.' % value)
+        elif l > 1:
+            raise ConfigurationError('There were multiple serializers found for value %r.' % value)
+        return serializers[0]

rest_framework/tests/relations_generic.py

@@ -0,0 +1,311 @@
+from __future__ import unicode_literals
+from django.contrib.contenttypes.models import ContentType
+from django.contrib.contenttypes.generic import GenericRelation, GenericForeignKey
+from django.core.exceptions import ValidationError
+from django.db import models
+from django.test import TestCase, RequestFactory
+
+from rest_framework import serializers
+from rest_framework.compat import patterns, url
+from rest_framework.exceptions import ConfigurationError
+from rest_framework.genericrelations import GenericRelatedField
+from rest_framework.reverse import reverse
+
+factory = RequestFactory()
+request = factory.get('/')  # Just to ensure we have a request in the serializer context
+
+def dummy_view(request, pk):
+    pass
+
+urlpatterns = patterns('',
+    url(r'^bookmark/(?P<pk>[0-9]+)/$', dummy_view, name='bookmark-detail'),
+    url(r'^note/(?P<pk>[0-9]+)/$', dummy_view, name='note-detail'),
+    url(r'^tag/(?P<pk>[0-9]+)/$', dummy_view, name='tag-detail'),
+    url(r'^contact/(?P<my_own_slug>[-\w]+)/$', dummy_view, name='contact-detail'),
+)
+
+
+class Tag(models.Model):
+    """
+    Tags have a descriptive slug, and are attached to an arbitrary object.
+    """
+    tag = models.SlugField()
+    content_type = models.ForeignKey(ContentType)
+    object_id = models.PositiveIntegerField()
+    tagged_item = GenericForeignKey('content_type', 'object_id')
+
+    def __unicode__(self):
+        return self.tag
+
+
+class Bookmark(models.Model):
+    """
+    A URL bookmark that may have multiple tags attached.
+    """
+    url = models.URLField()
+    tags = GenericRelation(Tag)
+
+    def __unicode__(self):
+        return 'Bookmark: %s' % self.url
+
+
+class Note(models.Model):
+    """
+    A textual note that may have multiple tags attached.
+    """
+    text = models.TextField()
+    tags = GenericRelation(Tag)
+
+    def __unicode__(self):
+        return 'Note: %s' % self.text
+
+
+class BookmarkSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = Bookmark
+        exclude = ('id', )
+
+
+class NoteSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = Note
+        exclude = ('id', )
+
+
+class TestGenericRelatedFieldDeserialization(TestCase):
+
+    urls = 'rest_framework.tests.relations_generic'
+
+    def setUp(self):
+        self.bookmark = Bookmark.objects.create(url='https://www.djangoproject.com/')
+        Tag.objects.create(tagged_item=self.bookmark, tag='django')
+        Tag.objects.create(tagged_item=self.bookmark, tag='python')
+        self.note = Note.objects.create(text='Remember the milk')
+        Tag.objects.create(tagged_item=self.note, tag='reminder')
+
+    def test_relations_as_hyperlinks(self):
+
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                    Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+                    Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+                }, source='tagged_item', read_only=True)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(Tag.objects.all(), many=True)
+        expected = [
+            {
+                'tagged_item': '/bookmark/1/',
+                'tag': 'django',
+            },
+            {
+                'tagged_item': '/bookmark/1/',
+                'tag': 'python',
+            },
+            {
+                'tagged_item': '/note/1/',
+                'tag': 'reminder'
+            }
+        ]
+        self.assertEqual(serializer.data, expected)
+
+    def test_relations_as_nested(self):
+
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                Bookmark: BookmarkSerializer(),
+                Note: NoteSerializer(),
+            }, source='tagged_item', read_only=True)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(Tag.objects.all(), many=True)
+        expected = [
+            {
+                'tagged_item': {
+                    'url': 'https://www.djangoproject.com/'
+                },
+                'tag': 'django'
+            },
+            {
+                'tagged_item': {
+                    'url': 'https://www.djangoproject.com/'
+                },
+                'tag': 'python'
+            },
+            {
+                'tagged_item': {
+                    'text': 'Remember the milk',
+                },
+                'tag': 'reminder'
+            }
+        ]
+        self.assertEqual(serializer.data, expected)
+
+    def test_mixed_serializers(self):
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                Bookmark: BookmarkSerializer(),
+                Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+            }, source='tagged_item', read_only=True)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(Tag.objects.all(), many=True)
+        expected = [
+            {
+                'tagged_item': {
+                    'url': 'https://www.djangoproject.com/'
+                },
+                'tag': 'django'
+            },
+            {
+                'tagged_item': {
+                    'url': 'https://www.djangoproject.com/'
+                },
+                'tag': 'python'
+            },
+            {
+                'tagged_item': '/note/1/',
+                'tag': 'reminder'
+            }
+        ]
+        self.assertEqual(serializer.data, expected)
+
+    def test_invalid_model(self):
+        # Leaving out the Note model should result in a ValidationError
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                Bookmark: BookmarkSerializer(),
+            }, source='tagged_item', read_only=True)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+        serializer = TagSerializer(Tag.objects.all(), many=True)
+
+        def call_data():
+            return serializer.data
+        self.assertRaises(ValidationError, call_data)
+
+
+class TestGenericRelatedFieldSerialization(TestCase):
+
+    urls = 'rest_framework.tests.relations_generic'
+
+    def setUp(self):
+        self.bookmark = Bookmark.objects.create(url='https://www.djangoproject.com/')
+        Tag.objects.create(tagged_item=self.bookmark, tag='django')
+        Tag.objects.create(tagged_item=self.bookmark, tag='python')
+        self.note = Note.objects.create(text='Remember the milk')
+
+    def test_hyperlink_serialization(self):
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                    Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+                    Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+                }, source='tagged_item', read_only=False)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(data={
+            'tag': 'reminder',
+            'tagged_item': reverse('note-detail', kwargs={'pk': self.note.pk})
+        })
+        serializer.is_valid()
+        expected = {
+            'tagged_item': '/note/1/',
+            'tag': 'reminder'
+        }
+        self.assertEqual(serializer.data, expected)
+
+    def test_configuration_error(self):
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                    Bookmark: BookmarkSerializer(),
+                    Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+                }, source='tagged_item', read_only=False)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(data={
+            'tag': 'reminder',
+            'tagged_item': 'just a string'
+        })
+
+        with self.assertRaises(ConfigurationError):
+            serializer.fields['tagged_item'].determine_serializer_for_data('just a string')
+
+    def test_not_registered_view_name(self):
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                    Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+                }, source='tagged_item', read_only=False)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(data={
+            'tag': 'reminder',
+            'tagged_item': reverse('note-detail', kwargs={'pk': self.note.pk})
+        })
+        self.assertFalse(serializer.is_valid())
+
+    def test_invalid_url(self):
+
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                    Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+                }, source='tagged_item', read_only=False)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(data={
+            'tag': 'reminder',
+            'tagged_item': 'foo-bar'
+        })
+
+        expected = {
+            'tagged_item': ['Could not determine a valid serializer for value %r.' % 'foo-bar']
+        }
+
+        self.assertFalse(serializer.is_valid())
+        self.assertEqual(expected, serializer.errors)
+
+    def test_serializer_save(self):
+        class TagSerializer(serializers.ModelSerializer):
+            tagged_item = GenericRelatedField({
+                    Bookmark: serializers.HyperlinkedRelatedField(view_name='bookmark-detail'),
+                    Note: serializers.HyperlinkedRelatedField(view_name='note-detail'),
+                }, source='tagged_item', read_only=False)
+
+            class Meta:
+                model = Tag
+                exclude = ('id', 'content_type', 'object_id', )
+
+        serializer = TagSerializer(data={
+            'tag': 'reminder',
+            'tagged_item': reverse('note-detail', kwargs={'pk': self.note.pk})
+        })
+        serializer.is_valid()
+        expected = {
+            'tagged_item': '/note/1/',
+            'tag': 'reminder'
+        }
+        serializer.save()
+        tag = Tag.objects.get(pk=3)
+        self.assertEqual(tag.tagged_item, self.note)