Fix crash with read-only polymorphic sub-serializer.

drf_spectacular/contrib/rest_polymorphic.py

@@ -14,8 +14,10 @@ def map_serializer(self, auto_schema, direction):
             sub_serializer = serializer._get_serializer_from_model_or_instance(sub_model)
             sub_serializer.partial = serializer.partial
             resource_type = serializer.to_resource_type(sub_model)
-            ref = auto_schema.resolve_serializer(sub_serializer, direction).ref
-            sub_components.append((resource_type, ref))
+            component = auto_schema.resolve_serializer(sub_serializer, direction)
+            if not component:
+                continue
+            sub_components.append((resource_type, component.ref))
 
             if not resource_type:
                 warn(

tests/contrib/test_rest_polymorphic.py

@@ -1,4 +1,6 @@
 # type: ignore
+from unittest import mock
+
 import pytest
 from django.db import models
 from rest_framework import serializers, viewsets
@@ -33,10 +35,17 @@ class NaturalPerson(Person):
     supervisor = models.ForeignKey('NaturalPerson', blank=True, null=True, on_delete=models.CASCADE)
 
 
+class NomadicPerson(Person):
+    @property
+    def address(self):
+        return 'Anywhere!'
+
+
 class PersonSerializer(PolymorphicSerializer):
     model_serializer_mapping = {
         LegalPerson: lazy_serializer('tests.contrib.test_rest_polymorphic.LegalPersonSerializer'),
         NaturalPerson: lazy_serializer('tests.contrib.test_rest_polymorphic.NaturalPersonSerializer'),
+        NomadicPerson: lazy_serializer('tests.contrib.test_rest_polymorphic.NomadicPersonSerializer'),
     }
 
     def to_resource_type(self, model_or_instance):
@@ -64,6 +73,15 @@ class Meta:
         fields = ('id', 'first_name', 'last_name', 'address', 'supervisor_id')
 
 
+class NomadicPersonSerializer(serializers.ModelSerializer):
+    # special case: all fields are read-only.
+    address = serializers.CharField(max_length=30, read_only=True)
+
+    class Meta:
+        model = NomadicPerson
+        fields = ('id', 'address')
+
+
 class PersonViewSet(viewsets.ModelViewSet):
     queryset = Person.objects.all()
     serializer_class = PersonSerializer
@@ -77,6 +95,23 @@ def test_rest_polymorphic(no_warnings):
     )
 
 
+@pytest.mark.contrib('polymorphic', 'rest_polymorphic')
+@mock.patch('drf_spectacular.settings.spectacular_settings.COMPONENT_SPLIT_REQUEST', True)
+def test_rest_polymorphic_split_request(no_warnings):
+    schema = generate_schema('persons', PersonViewSet)
+    names = set(schema['components']['schemas'])
+    assert 'LegalPersonRequest' in names
+    assert 'NaturalPersonRequest' in names
+    assert 'NomadicPersonRequest' not in names  # All fields were read-only.
+    assert 'PatchedLegalPersonRequest' in names
+    assert 'PatchedNaturalPersonRequest' in names
+    assert 'PatchedNomadicPersonRequest' not in names  # All fields were read-only.
+    assert_schema(
+        generate_schema('persons', PersonViewSet),
+        'tests/contrib/test_rest_polymorphic_split_request.yml',
+    )
+
+
 @pytest.mark.contrib('polymorphic', 'rest_polymorphic')
 @pytest.mark.django_db
 def test_model_setup_is_valid():

tests/contrib/test_rest_polymorphic.yml

@@ -202,6 +202,19 @@ components:
       - id
       - last_name
       - supervisor_id
+    NomadicPerson:
+      type: object
+      properties:
+        id:
+          type: integer
+          readOnly: true
+        address:
+          type: string
+          readOnly: true
+          maxLength: 30
+      required:
+      - address
+      - id
     PatchedLegalPerson:
       type: object
       properties:
@@ -237,24 +250,38 @@ components:
         supervisor_id:
           type: integer
           nullable: true
+    PatchedNomadicPerson:
+      type: object
+      properties:
+        id:
+          type: integer
+          readOnly: true
+        address:
+          type: string
+          readOnly: true
+          maxLength: 30
     PatchedPerson:
       oneOf:
       - $ref: '#/components/schemas/PatchedLegalPerson'
       - $ref: '#/components/schemas/PatchedNaturalPerson'
+      - $ref: '#/components/schemas/PatchedNomadicPerson'
       discriminator:
         propertyName: resourcetype
         mapping:
           legal: '#/components/schemas/PatchedLegalPerson'
           natural: '#/components/schemas/PatchedNaturalPerson'
+          nomadic: '#/components/schemas/PatchedNomadicPerson'
     Person:
       oneOf:
       - $ref: '#/components/schemas/LegalPerson'
       - $ref: '#/components/schemas/NaturalPerson'
+      - $ref: '#/components/schemas/NomadicPerson'
       discriminator:
         propertyName: resourcetype
         mapping:
           legal: '#/components/schemas/LegalPerson'
           natural: '#/components/schemas/NaturalPerson'
+          nomadic: '#/components/schemas/NomadicPerson'
   securitySchemes:
     basicAuth:
       type: http