Fix inheritance bugs with @extend_schema_view().

When creating a copy of a method from a parent class we now:

- Ensure that `__qualname__` is defined correctly
  - i.e. `Child.method` instead of `Parent.method`.
  - This isn't essential but helps diagnosing issues when debugging.
- Move application of the decorator to the last moment.
- Deep copy the existing schema extensions before applying decorator.

This fixes tfranzel#218 where two child classes with @extend_schema_view affect
each other - schema extensions are applied to the parent such that the
second child overwrites the changes applied to the first child.

This also fixes my case where a child with @extend_schema_view clobbered
the schema extensions of the parent which also used @extend_schema_view.

drf_spectacular/utils.py

@@ -1,6 +1,7 @@
 import functools
 import inspect
 import sys
+from copy import deepcopy
 from typing import Any, Callable, Dict, List, Optional, Tuple, Type, TypeVar, Union
 
 from rest_framework.fields import Field, empty
@@ -469,13 +470,20 @@ def extend_schema_view(**kwargs) -> Callable[[F], F]:
     :param kwargs: method names as argument names and :func:`@extend_schema <.extend_schema>`
       calls as values
     """
-    def wrapping_decorator(method_decorator, method):
-        @method_decorator
+    def wrapping_decorator(method_decorator, view, method):
         @functools.wraps(method)
         def wrapped_method(self, request, *args, **kwargs):
             return method(self, request, *args, **kwargs)
 
-        return wrapped_method
+        # Construct a new __qualname__ based on the __name__ of the target view.
+        wrapped_method.__qualname__ = f'{view.__name__}.{method.__name__}'
+
+        # Clone the extended schema if the source method has it.
+        if hasattr(method, 'kwargs'):
+            wrapped_method.kwargs = deepcopy(method.kwargs)
+
+        # Finally apply any additional schema extensions applied to the target view.
+        return method_decorator(wrapped_method)
 
     def decorator(view):
         view_methods = {m.__name__: m for m in get_view_methods(view)}
@@ -495,7 +503,7 @@ def decorator(view):
             if method_name in view.__dict__:
                 method_decorator(method)
             else:
-                setattr(view, method_name, wrapping_decorator(method_decorator, method))
+                setattr(view, method_name, wrapping_decorator(method_decorator, view, method))
         return view
 
     return decorator

tests/test_extend_schema_view.py

@@ -28,7 +28,7 @@ class Meta:
     extended_action=extend_schema(description='view extended action description'),
     raw_action=extend_schema(description='view raw action description'),
 )
-class XViewset(mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet):
+class XViewSet(mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet):
     queryset = ESVModel.objects.all()
     serializer_class = ESVSerializer
 
@@ -52,9 +52,67 @@ class YViewSet(viewsets.ModelViewSet):
     queryset = ESVModel.objects.all()
 
 
+# view to make sure that schema applied to a subclass does not affect its parent.
+@extend_schema_view(
+    list=extend_schema(exclude=True),
+    retrieve=extend_schema(description='overridden description for child only'),
+    extended_action=extend_schema(responses={200: {'type': 'string', 'pattern': r'^[0-9]{4}(?:-[0-9]{2}){2}$'}}),
+    raw_action=extend_schema(summary="view raw action summary"),
+)
+class ZViewSet(XViewSet):
+    @extend_schema(tags=['child-tag'])
+    @action(detail=False, methods=['GET'])
+    def raw_action(self, request):
+        return Response('2019-03-01')
+
+
+class Appointment(models.Model):
+    pass
+
+
+class AppointmentSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = Appointment
+        fields = '__all__'
+
+
+class AppointmentViewSet(viewsets.GenericViewSet):
+    serializer_class = AppointmentSerializer
+    queryset = Appointment.objects.all()
+
+    @action(detail=False)
+    def notes(self, request):
+        return Response(['A note.'])
+
+
+@extend_schema_view(
+    notes=extend_schema(
+        tags=["Doctor Appointments"],
+        summary="Get appointment notes",
+        description="Retrieves the detailed appointment notes as written by the doctor.",
+    ),
+)
+class DoctorAppointmentViewSet(AppointmentViewSet):
+    pass
+
+
+@extend_schema_view(
+    notes=extend_schema(
+        tags=["Patient Appointments"],
+        summary="Get appointment notes",
+        description="Retrieves the summarized appointment notes for viewing by the patient.",
+    ),
+)
+class PatientAppointmentViewSet(AppointmentViewSet):
+    pass
+
+
 router = routers.SimpleRouter()
-router.register('x', XViewset)
+router.register('x', XViewSet)
 router.register('y', YViewSet)
+router.register('z', ZViewSet)
+router.register('api/doctors', DoctorAppointmentViewSet)
+router.register('api/patients', PatientAppointmentViewSet)
 urlpatterns = router.urls
 
 

tests/test_extend_schema_view.yml

@@ -3,6 +3,42 @@ info:
   title: ''
   version: 0.0.0
 paths:
+  /api/doctors/notes/:
+    get:
+      operationId: api_doctors_notes_retrieve
+      description: Retrieves the detailed appointment notes as written by the doctor.
+      summary: Get appointment notes
+      tags:
+      - Doctor Appointments
+      security:
+      - cookieAuth: []
+      - basicAuth: []
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Appointment'
+          description: ''
+  /api/patients/notes/:
+    get:
+      operationId: api_patients_notes_retrieve
+      description: Retrieves the summarized appointment notes for viewing by the patient.
+      summary: Get appointment notes
+      tags:
+      - Patient Appointments
+      security:
+      - cookieAuth: []
+      - basicAuth: []
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Appointment'
+          description: ''
   /x/:
     get:
       operationId: x_list
@@ -232,8 +268,75 @@ paths:
       responses:
         '204':
           description: No response body
+  /z/{id}/:
+    get:
+      operationId: z_retrieve
+      description: overridden description for child only
+      parameters:
+      - in: path
+        name: id
+        schema:
+          type: integer
+        description: A unique integer value identifying this esv model.
+        required: true
+      tags:
+      - custom-retrieve-tag
+      security:
+      - cookieAuth: []
+      - basicAuth: []
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ESV'
+          description: ''
+  /z/extended_action/:
+    get:
+      operationId: z_extended_action_retrieve
+      description: view extended action description
+      tags:
+      - global-tag
+      security:
+      - cookieAuth: []
+      - basicAuth: []
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                type: string
+                pattern: ^[0-9]{4}(?:-[0-9]{2}){2}$
+          description: ''
+  /z/raw_action/:
+    get:
+      operationId: z_raw_action_retrieve
+      summary: view raw action summary
+      tags:
+      - child-tag
+      security:
+      - cookieAuth: []
+      - basicAuth: []
+      - {}
+      responses:
+        '200':
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ESV'
+          description: ''
 components:
   schemas:
+    Appointment:
+      type: object
+      properties:
+        id:
+          type: integer
+          readOnly: true
+      required:
+      - id
     ESV:
       type: object
       properties: