Support polymorphic models

.gitignore

@@ -33,6 +33,8 @@ pip-delete-this-directory.txt
 
 # Tox
 .tox/
+.cache/
+.python-version
 
 # VirtualEnv
 .venv/

.travis.yml

@@ -26,8 +26,9 @@ env:
 
   - DJANGO=">=1.10,<1.11" DRF=">=3.4,<3.5"
 before_install:
-  # Force an upgrade of py to avoid VersionConflict
+  # Force an upgrade of py & pytest to avoid VersionConflict
   - pip install --upgrade py
+  - pip install "pytest>=2.8,<3"
   - pip install codecov
 install:
   - pip install Django${DJANGO} djangorestframework${DRF}

docs/usage.md

@@ -423,6 +423,63 @@ field_name_mapping = {
 ```
 
 
+### Working with polymorphic resources
+
+#### Extraction of the polymorphic type
+
+This package can defer the resolution of the type of polymorphic models instances to retrieve the appropriate type.
+However, most models are not polymorphic and for performance reasons this is only done if the underlying model is a subclass of a polymorphic model.
+
+Polymorphic ancestors must be defined on settings like this:
+
+```python
+JSON_API_POLYMORPHIC_ANCESTORS = (
+    'polymorphic.models.PolymorphicModel',
+)
+```
+
+#### Writing polymorphic resources
+
+A polymorphic endpoint can be setup if associated with a polymorphic serializer.
+A polymorphic serializer take care of (de)serializing the correct instances types and can be defined like this:
+
+```python
+class ProjectSerializer(serializers.PolymorphicModelSerializer):
+    polymorphic_serializers = [ArtProjectSerializer, ResearchProjectSerializer]
+
+    class Meta:
+        model = models.Project
+```
+
+It must inherit from `serializers.PolymorphicModelSerializer` and define the `polymorphic_serializers` list.
+This attribute defines the accepted resource types.
+
+
+Polymorphic relations can also be handled with `relations.PolymorphicResourceRelatedField` like this:
+
+```python
+class CompanySerializer(serializers.ModelSerializer):
+    current_project = relations.PolymorphicResourceRelatedField(
+        ProjectSerializer, queryset=models.Project.objects.all())
+    future_projects = relations.PolymorphicResourceRelatedField(
+        ProjectSerializer, queryset=models.Project.objects.all(), many=True)
+
+    class Meta:
+        model = models.Company
+```
+
+They must be explicitely declared with the `polymorphic_serializer` (first positional argument) correctly defined.
+It must be a subclass of `serializers.PolymorphicModelSerializer`.
+
+<div class="warning">
+    <strong>Note:</strong>
+    Polymorphic resources are not compatible with
+    <code class="docutils literal">
+        <span class="pre">resource_name</span>
+    </code>
+    defined on the view.
+</div>
+
 ### Meta
 
 You may add metadata to the rendered json in two different ways: `meta_fields` and `get_root_meta`.

example/factories/__init__.py

@@ -2,21 +2,23 @@
 
 import factory
 from faker import Factory as FakerFactory
-from example.models import Blog, Author, AuthorBio, Entry, Comment
+from example import models
+
 
 faker = FakerFactory.create()
 faker.seed(983843)
 
+
 class BlogFactory(factory.django.DjangoModelFactory):
     class Meta:
-        model = Blog
+        model = models.Blog
 
     name = factory.LazyAttribute(lambda x: faker.name())
 
 
 class AuthorFactory(factory.django.DjangoModelFactory):
     class Meta:
-        model = Author
+        model = models.Author
 
     name = factory.LazyAttribute(lambda x: faker.name())
     email = factory.LazyAttribute(lambda x: faker.email())
@@ -25,15 +27,15 @@ class Meta:
 
 class AuthorBioFactory(factory.django.DjangoModelFactory):
     class Meta:
-        model = AuthorBio
+        model = models.AuthorBio
 
     author = factory.SubFactory(AuthorFactory)
     body = factory.LazyAttribute(lambda x: faker.text())
 
 
 class EntryFactory(factory.django.DjangoModelFactory):
     class Meta:
-        model = Entry
+        model = models.Entry
 
     headline = factory.LazyAttribute(lambda x: faker.sentence(nb_words=4))
     body_text = factory.LazyAttribute(lambda x: faker.text())
@@ -52,9 +54,40 @@ def authors(self, create, extracted, **kwargs):
 
 class CommentFactory(factory.django.DjangoModelFactory):
     class Meta:
-        model = Comment
+        model = models.Comment
 
     entry = factory.SubFactory(EntryFactory)
     body = factory.LazyAttribute(lambda x: faker.text())
     author = factory.SubFactory(AuthorFactory)
 
+
+class ArtProjectFactory(factory.django.DjangoModelFactory):
+    class Meta:
+        model = models.ArtProject
+
+    topic = factory.LazyAttribute(lambda x: faker.catch_phrase())
+    artist = factory.LazyAttribute(lambda x: faker.name())
+
+
+class ResearchProjectFactory(factory.django.DjangoModelFactory):
+    class Meta:
+        model = models.ResearchProject
+
+    topic = factory.LazyAttribute(lambda x: faker.catch_phrase())
+    supervisor = factory.LazyAttribute(lambda x: faker.name())
+
+
+class CompanyFactory(factory.django.DjangoModelFactory):
+    class Meta:
+        model = models.Company
+
+    name = factory.LazyAttribute(lambda x: faker.company())
+    current_project = factory.SubFactory(ArtProjectFactory)
+
+    @factory.post_generation
+    def future_projects(self, create, extracted, **kwargs):
+        if not create:
+            return
+        if extracted:
+            for project in extracted:
+                self.future_projects.add(project)

example/migrations/0002_auto_20160513_0857.py

@@ -0,0 +1,80 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.6 on 2016-05-13 08:57
+from __future__ import unicode_literals
+from distutils.version import LooseVersion
+
+from django.db import migrations, models
+import django.db.models.deletion
+import django
+
+
+class Migration(migrations.Migration):
+
+    # TODO: Must be removed as soon as Django 1.7 support is dropped
+    if django.get_version() < LooseVersion('1.8'):
+        dependencies = [
+            ('contenttypes', '0001_initial'),
+            ('example', '0001_initial'),
+        ]
+    else:
+        dependencies = [
+            ('contenttypes', '0002_remove_content_type_name'),
+            ('example', '0001_initial'),
+        ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Company',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=100)),
+            ],
+        ),
+        migrations.CreateModel(
+            name='Project',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('topic', models.CharField(max_length=30)),
+            ],
+            options={
+                'abstract': False,
+            },
+        ),
+        migrations.CreateModel(
+            name='ArtProject',
+            fields=[
+                ('project_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='example.Project')),
+                ('artist', models.CharField(max_length=30)),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=('example.project',),
+        ),
+        migrations.CreateModel(
+            name='ResearchProject',
+            fields=[
+                ('project_ptr', models.OneToOneField(auto_created=True, on_delete=django.db.models.deletion.CASCADE, parent_link=True, primary_key=True, serialize=False, to='example.Project')),
+                ('supervisor', models.CharField(max_length=30)),
+            ],
+            options={
+                'abstract': False,
+            },
+            bases=('example.project',),
+        ),
+        migrations.AddField(
+            model_name='project',
+            name='polymorphic_ctype',
+            field=models.ForeignKey(editable=False, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='polymorphic_example.project_set+', to='contenttypes.ContentType'),
+        ),
+        migrations.AddField(
+            model_name='company',
+            name='current_project',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='companies', to='example.Project'),
+        ),
+        migrations.AddField(
+            model_name='company',
+            name='future_projects',
+            field=models.ManyToManyField(to='example.Project'),
+        ),
+    ]

example/models.py

@@ -3,6 +3,7 @@
 
 from django.db import models
 from django.utils.encoding import python_2_unicode_compatible
+from polymorphic.models import PolymorphicModel
 
 
 class BaseModel(models.Model):
@@ -72,3 +73,24 @@ class Comment(BaseModel):
     def __str__(self):
         return self.body
 
+
+class Project(PolymorphicModel):
+    topic = models.CharField(max_length=30)
+
+
+class ArtProject(Project):
+    artist = models.CharField(max_length=30)
+
+
+class ResearchProject(Project):
+    supervisor = models.CharField(max_length=30)
+
+
+@python_2_unicode_compatible
+class Company(models.Model):
+    name = models.CharField(max_length=100)
+    current_project = models.ForeignKey(Project, related_name='companies')
+    future_projects = models.ManyToManyField(Project)
+
+    def __str__(self):
+        return self.name