Removed support exposing Polymorphic resources as JSON:API endpoints (#1336)

This has been deprecated since version 8.1.0 (one year ago) and will now
be removed.

Author: sliverc

CHANGELOG.md

@@ -25,6 +25,10 @@ any parts of the framework not mentioned in the documentation should generally b
 * Removed support for Django 4.2.
 * Removed support for Django 5.1.
 
+### Removed
+
+* Removed support for exposing Polymorphic resources through [django-polymorphic](https://github.com/django-commons/django-polymorphic) as JSON:API endpoints.
+
 ## [8.1.0] - 2025-10-17
 
 This is the last release supporting Python 3.9, Django 4.2, Django 5.1, Django REST framework 3.15 and Django REST framework 3.16.
@@ -39,7 +43,7 @@ This is the last release supporting Python 3.9, Django 4.2, Django 5.1, Django R
 
 ### Deprecated
 
-* Deprecated support for exposing Polymorphic resources through [django-polymorphic](https://github.com/jazzband/django-polymorphic) as JSON:API endpoints.
+* Deprecated support for exposing Polymorphic resources through [django-polymorphic](https://github.com/django-commons/django-polymorphic) as JSON:API endpoints.
   There is currently no replacement. In case you are affected of this change please
   join [our discussion](https://github.com/django-json-api/django-rest-framework-json-api/discussions/1194).
 

README.rst

@@ -113,7 +113,6 @@ Install using ``pip``...
     $ pip install djangorestframework-jsonapi
     $ # for optional package integrations
     $ pip install djangorestframework-jsonapi['django-filter']
-    $ pip install djangorestframework-jsonapi['django-polymorphic']
 
 
 or from source...

docs/getting-started.md

@@ -68,7 +68,6 @@ Install using `pip`...
     pip install djangorestframework-jsonapi
     # for optional package integrations
     pip install djangorestframework-jsonapi['django-filter']
-    pip install djangorestframework-jsonapi['django-polymorphic']
 
 or from source...
 

docs/usage.md

@@ -874,74 +874,6 @@ field_name_mapping = {
     }
 ```
 
-### Working with polymorphic resources
-
---
-
-**Deprecation notice:**
-
-
-Support for using Polymorphic resources through [django-polymorphic](https://github.com/jazzband/django-polymorphic) is deprecated and will be removed in a future release.
-
-There is currently no replacement. In case you are affected of this change please join [our discussion](https://github.com/django-json-api/django-rest-framework-json-api/discussions/1194).
-
----
-
-Polymorphic resources allow you to use specialized subclasses without requiring
-special endpoints to expose the specialized versions. For example, if you had a
-`Project` that could be either an `ArtProject` or a `ResearchProject`, you can
-have both kinds at the same URL.
-
-DJA tests its polymorphic support against [django-polymorphic](https://django-polymorphic.readthedocs.io/en/stable/).
-The polymorphic feature should also work with other popular libraries like
-django-polymodels or django-typed-models.
-
-As this feature depends on `django-polymorphic` you need to run
-
-    pip install djangorestframework-jsonapi['django-polymorphic']
-
-#### Writing polymorphic resources
-
-A polymorphic endpoint can be set up if associated with a polymorphic serializer.
-A polymorphic serializer takes 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 explicitly 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.py

@@ -2,18 +2,15 @@
 from faker import Factory as FakerFactory
 
 from example.models import (
-    ArtProject,
     Author,
     AuthorBio,
     AuthorBioMetadata,
     AuthorType,
     Blog,
     Comment,
-    Company,
     Entry,
     ProjectType,
     Questionnaire,
-    ResearchProject,
     TaggedItem,
 )
 
@@ -112,41 +109,6 @@ class Meta:
     name = factory.LazyAttribute(lambda x: faker.name())
 
 
-class ArtProjectFactory(factory.django.DjangoModelFactory):
-    class Meta:
-        model = ArtProject
-
-    topic = factory.LazyAttribute(lambda x: faker.catch_phrase())
-    artist = factory.LazyAttribute(lambda x: faker.name())
-    project_type = factory.SubFactory(ProjectTypeFactory)
-
-
-class ResearchProjectFactory(factory.django.DjangoModelFactory):
-    class Meta:
-        model = ResearchProject
-
-    topic = factory.LazyAttribute(lambda x: faker.catch_phrase())
-    supervisor = factory.LazyAttribute(lambda x: faker.name())
-    project_type = factory.SubFactory(ProjectTypeFactory)
-
-
-class CompanyFactory(factory.django.DjangoModelFactory):
-    class Meta:
-        model = Company
-        skip_postgeneration_save = True
-
-    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:  # pragma: no cover
-            return
-        if extracted:
-            for project in extracted:
-                self.future_projects.add(project)
-
-
 class QuestionnaireFactory(factory.django.DjangoModelFactory):
     class Meta:
         model = Questionnaire

example/migrations/0015_remove_company_current_project_and_more.py

@@ -0,0 +1,56 @@
+# Generated by Django 6.0.7 on 2026-10-08 02:18
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("example", "0014_questionnaire_metadata"),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name="company",
+            name="current_project",
+        ),
+        migrations.RemoveField(
+            model_name="company",
+            name="future_projects",
+        ),
+        migrations.RemoveField(
+            model_name="labresults",
+            name="author",
+        ),
+        migrations.RemoveField(
+            model_name="labresults",
+            name="research_project",
+        ),
+        migrations.RemoveField(
+            model_name="project",
+            name="polymorphic_ctype",
+        ),
+        migrations.RemoveField(
+            model_name="project",
+            name="project_type",
+        ),
+        migrations.RemoveField(
+            model_name="researchproject",
+            name="project_ptr",
+        ),
+        migrations.DeleteModel(
+            name="ArtProject",
+        ),
+        migrations.DeleteModel(
+            name="Company",
+        ),
+        migrations.DeleteModel(
+            name="LabResults",
+        ),
+        migrations.DeleteModel(
+            name="Project",
+        ),
+        migrations.DeleteModel(
+            name="ResearchProject",
+        ),
+    ]

example/models.py

@@ -1,7 +1,6 @@
 from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
 from django.contrib.contenttypes.models import ContentType
 from django.db import models
-from polymorphic.models import PolymorphicModel
 
 
 class BaseModel(models.Model):
@@ -139,49 +138,6 @@ class Meta:
         ordering = ("id",)
 
 
-class Project(PolymorphicModel):
-    topic = models.CharField(max_length=30)
-    project_type = models.ForeignKey(ProjectType, null=True, on_delete=models.CASCADE)
-
-
-class ArtProject(Project):
-    artist = models.CharField(max_length=30)
-    description = models.CharField(max_length=100, null=True)
-
-
-class ResearchProject(Project):
-    supervisor = models.CharField(max_length=30)
-
-
-class LabResults(models.Model):
-    research_project = models.ForeignKey(
-        ResearchProject, related_name="lab_results", on_delete=models.CASCADE
-    )
-    date = models.DateField()
-    measurements = models.TextField()
-    author = models.ForeignKey(
-        Author,
-        null=True,
-        blank=True,
-        on_delete=models.CASCADE,
-        related_name="lab_results",
-    )
-
-    class Meta:
-        ordering = ("id",)
-
-
-class Company(models.Model):
-    name = models.CharField(max_length=100)
-    current_project = models.ForeignKey(
-        Project, related_name="companies", on_delete=models.CASCADE
-    )
-    future_projects = models.ManyToManyField(Project)
-
-    def __str__(self):
-        return self.name
-
-
 class Questionnaire(models.Model):
     name = models.CharField(max_length=100)
     questions = models.JSONField()

example/serializers.py

@@ -1,25 +1,19 @@
 from datetime import datetime
 
-from rest_framework import fields as drf_fields
 from rest_framework import serializers as drf_serilazers
 
 from rest_framework_json_api import relations, serializers
 
 from example.models import (
-    ArtProject,
     Author,
     AuthorBio,
     AuthorBioMetadata,
     AuthorType,
     Blog,
     Comment,
-    Company,
     Entry,
-    LabResults,
-    Project,
     ProjectType,
     Questionnaire,
-    ResearchProject,
     TaggedItem,
 )
 
@@ -347,83 +341,6 @@ class BaseProjectSerializer(serializers.ModelSerializer):
     }
 
 
-class ArtProjectSerializer(BaseProjectSerializer):
-    class Meta:
-        model = ArtProject
-        exclude = ("polymorphic_ctype",)
-
-
-class ResearchProjectSerializer(BaseProjectSerializer):
-    # testing exclusive related field on inherited polymorphic model
-    lab_results = relations.ResourceRelatedField(many=True, read_only=True)
-
-    class Meta:
-        model = ResearchProject
-        exclude = ("polymorphic_ctype",)
-
-
-class LabResultsSerializer(serializers.ModelSerializer):
-    included_serializers = {"author": AuthorSerializer}
-
-    class Meta:
-        model = LabResults
-        fields = ("date", "measurements", "author")
-
-
-class ProjectSerializer(serializers.PolymorphicModelSerializer):
-    included_serializers = {
-        "project_type": ProjectTypeSerializer,
-    }
-    polymorphic_serializers = [ArtProjectSerializer, ResearchProjectSerializer]
-
-    class Meta:
-        model = Project
-        exclude = ("polymorphic_ctype",)
-
-
-class CurrentProjectRelatedField(relations.PolymorphicResourceRelatedField):
-    def get_attribute(self, instance):
-        obj = super().get_attribute(instance)
-
-        is_art = self.field_name == "current_art_project" and isinstance(
-            obj, ArtProject
-        )
-        is_res = self.field_name == "current_research_project" and isinstance(
-            obj, ResearchProject
-        )
-
-        if is_art or is_res:
-            return obj
-
-        raise drf_fields.SkipField()
-
-
-class CompanySerializer(serializers.ModelSerializer):
-    current_project = relations.PolymorphicResourceRelatedField(
-        ProjectSerializer, queryset=Project.objects.all()
-    )
-    current_art_project = CurrentProjectRelatedField(
-        ProjectSerializer, source="current_project", read_only=True
-    )
-    current_research_project = CurrentProjectRelatedField(
-        ProjectSerializer, source="current_project", read_only=True
-    )
-    future_projects = relations.PolymorphicResourceRelatedField(
-        ProjectSerializer, queryset=Project.objects.all(), many=True
-    )
-
-    included_serializers = {
-        "current_project": ProjectSerializer,
-        "future_projects": ProjectSerializer,
-        "current_art_project": ProjectSerializer,
-        "current_research_project": ProjectSerializer,
-    }
-
-    class Meta:
-        model = Company
-        fields = "__all__"
-
-
 class QuestionSerializer(serializers.Serializer):
     text = serializers.CharField()
     required = serializers.BooleanField(default=False)