Fix schema generation for nested serializers (#1177)

* Fix Serializer schema generation when used as a ListField child
* Fix Serializer schema generation when used in another serializer

Author: arttuperala

CHANGELOG.md

@@ -8,6 +8,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Note that in line with [Django REST framework policy](https://www.django-rest-framework.org/topics/release-notes/),
 any parts of the framework not mentioned in the documentation should generally be considered private API, and may be subject to change.
 
+## [Unreleased]
+
+### Fixed
+
+* Fixed OpenAPI schema generation for `Serializer` when used inside another `Serializer` or as a child of `ListField`.
+
 ## [6.1.0] - 2023-08-25
 
 ### Added

example/factories.py

@@ -12,6 +12,7 @@
     Company,
     Entry,
     ProjectType,
+    Questionnaire,
     ResearchProject,
     TaggedItem,
 )
@@ -140,3 +141,24 @@ def future_projects(self, create, extracted, **kwargs):
         if extracted:
             for project in extracted:
                 self.future_projects.add(project)
+
+
+class QuestionnaireFactory(factory.django.DjangoModelFactory):
+    class Meta:
+        model = Questionnaire
+
+    name = factory.LazyAttribute(lambda x: faker.text())
+    questions = [
+        {
+            "text": "What is your name?",
+            "required": True,
+        },
+        {
+            "text": "What is your quest?",
+            "required": False,
+        },
+        {
+            "text": "What is the air-speed velocity of an unladen swallow?",
+        },
+    ]
+    metadata = {"author": "Bridgekeeper"}

example/migrations/0013_questionnaire.py

@@ -0,0 +1,28 @@
+# Generated by Django 4.2.5 on 2023-09-07 02:35
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("example", "0012_author_full_name"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="Questionnaire",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("name", models.CharField(max_length=100)),
+                ("questions", models.JSONField()),
+            ],
+        ),
+    ]

example/migrations/0014_questionnaire_metadata.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.5 on 2023-09-12 07:12
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("example", "0013_questionnaire"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="questionnaire",
+            name="metadata",
+            field=models.JSONField(default={}),
+            preserve_default=False,
+        ),
+    ]

example/models.py

@@ -180,3 +180,9 @@ class Company(models.Model):
 
     def __str__(self):
         return self.name
+
+
+class Questionnaire(models.Model):
+    name = models.CharField(max_length=100)
+    questions = models.JSONField()
+    metadata = models.JSONField()

example/serializers.py

@@ -18,6 +18,7 @@
     LabResults,
     Project,
     ProjectType,
+    Questionnaire,
     ResearchProject,
     TaggedItem,
 )
@@ -421,3 +422,22 @@ class CompanySerializer(serializers.ModelSerializer):
     class Meta:
         model = Company
         fields = "__all__"
+
+
+class QuestionSerializer(serializers.Serializer):
+    text = serializers.CharField()
+    required = serializers.BooleanField(default=False)
+
+
+class QuestionnaireMetadataSerializer(serializers.Serializer):
+    author = serializers.CharField()
+    producer = serializers.CharField(default=None)
+
+
+class QuestionnaireSerializer(serializers.ModelSerializer):
+    questions = serializers.ListField(child=QuestionSerializer())
+    metadata = QuestionnaireMetadataSerializer()
+
+    class Meta:
+        model = Questionnaire
+        fields = ("name", "questions", "metadata")

example/tests/conftest.py

@@ -12,6 +12,7 @@
     CommentFactory,
     CompanyFactory,
     EntryFactory,
+    QuestionnaireFactory,
     ResearchProjectFactory,
     TaggedItemFactory,
 )
@@ -27,6 +28,7 @@
 register(ArtProjectFactory)
 register(ResearchProjectFactory)
 register(CompanyFactory)
+register(QuestionnaireFactory)
 
 
 @pytest.fixture

example/tests/test_openapi.py

@@ -125,6 +125,46 @@ def test_schema_id_field():
     assert "id" not in company_properties["attributes"]["properties"]
 
 
+def test_schema_subserializers():
+    """Schema for child Serializers reflects the actual response structure."""
+    patterns = [
+        re_path(
+            "^questionnaires/?$", views.QuestionnaireViewset.as_view({"get": "list"})
+        ),
+    ]
+    generator = SchemaGenerator(patterns=patterns)
+
+    request = create_request("/")
+    schema = generator.get_schema(request=request)
+
+    assert {
+        "type": "object",
+        "properties": {
+            "metadata": {
+                "type": "object",
+                "properties": {
+                    "author": {"type": "string"},
+                    "producer": {"type": "string"},
+                },
+                "required": ["author"],
+            },
+            "questions": {
+                "type": "array",
+                "items": {
+                    "type": "object",
+                    "properties": {
+                        "text": {"type": "string"},
+                        "required": {"type": "boolean", "default": False},
+                    },
+                    "required": ["text"],
+                },
+            },
+            "name": {"type": "string", "maxLength": 100},
+        },
+        "required": ["name", "questions", "metadata"],
+    } == schema["components"]["schemas"]["Questionnaire"]["properties"]["attributes"]
+
+
 def test_schema_parameters_include():
     """Include paramater is only used when serializer defines included_serializers."""
     patterns = [

example/tests/test_serializers.py

@@ -224,6 +224,39 @@ def test_model_serializer_with_implicit_fields(self, comment, client):
         assert response.status_code == 200
         assert expected == response.json()
 
+    def test_model_serializer_with_subserializers(self, questionnaire, client):
+        expected = {
+            "data": {
+                "type": "questionnaires",
+                "id": str(questionnaire.pk),
+                "attributes": {
+                    "name": questionnaire.name,
+                    "questions": [
+                        {
+                            "text": "What is your name?",
+                            "required": True,
+                        },
+                        {
+                            "text": "What is your quest?",
+                            "required": False,
+                        },
+                        {
+                            "text": "What is the air-speed velocity of an unladen swallow?",
+                            "required": False,
+                        },
+                    ],
+                    "metadata": {"author": "Bridgekeeper", "producer": None},
+                },
+            },
+        }
+
+        response = client.get(
+            reverse("questionnaire-detail", kwargs={"pk": questionnaire.pk})
+        )
+
+        assert response.status_code == 200
+        assert expected == response.json()
+
 
 class TestPolymorphicModelSerializer(TestCase):
     def setUp(self):

example/urls.py

@@ -19,6 +19,7 @@
     NonPaginatedEntryViewSet,
     ProjectTypeViewset,
     ProjectViewset,
+    QuestionnaireViewset,
 )
 
 router = routers.DefaultRouter(trailing_slash=False)
@@ -32,6 +33,7 @@
 router.register(r"projects", ProjectViewset)
 router.register(r"project-types", ProjectTypeViewset)
 router.register(r"lab-results", LabResultViewSet)
+router.register(r"questionnaires", QuestionnaireViewset)
 
 urlpatterns = [
     path("", include(router.urls)),