add expressive error in case of misconfiguration #156

drf_spectacular/generators.py

@@ -7,6 +7,7 @@
 from rest_framework.schemas.generators import EndpointEnumerator as BaseEndpointEnumerator
 
 from drf_spectacular.extensions import OpenApiViewExtension
+from drf_spectacular.openapi import AutoSchema
 from drf_spectacular.plumbing import (
     ComponentRegistry, alpha_operation_sorter, build_root_object, camelize_operation, error,
     is_versioning_supported, modify_for_versioning, normalize_result_object,
@@ -149,7 +150,11 @@ def parse(self, request, public):
                 if not version or not operation_matches_version(view, version):
                     continue
 
-            # beware that every access to schema yields a fresh object (descriptor pattern)
+            assert isinstance(view.schema, AutoSchema), (
+                f'Incompatible AutoSchema used on View. Is DRF\'s DEFAULT_SCHEMA_CLASS '
+                f'pointing to "drf_spectacular.openapi.AutoSchema" or any other drf-spectacular '
+                f'compatible AutoSchema?'
+            )
             operation = view.schema.get_operation(path, path_regex, method, self.registry)
 
             # operation was manually removed via @extend_schema

tests/test_warnings.py

@@ -1,8 +1,12 @@
+from unittest import mock
+
+import pytest
 from django.db import models
 from django.urls import path
 from rest_framework import mixins, serializers, views, viewsets
 from rest_framework.authentication import BaseAuthentication
 from rest_framework.decorators import action, api_view
+from rest_framework.schemas import AutoSchema as DRFAutoSchema
 from rest_framework.views import APIView
 
 from drf_spectacular.generators import SchemaGenerator
@@ -219,3 +223,15 @@ def view_func(request, format=None):
     assert schema['paths']['/pi/']['get']['operationId'] == 'pi_retrieve'
     assert schema['paths']['/pi/{foo}']['get']['operationId'] == 'pi_retrieve_2'
     assert 'operationId "pi_retrieve" has collisions' in capsys.readouterr().err
+
+
+@mock.patch('rest_framework.settings.api_settings.DEFAULT_SCHEMA_CLASS', DRFAutoSchema)
+def test_compatible_auto_schema_class_on_view(no_warnings):
+    @extend_schema(responses=OpenApiTypes.FLOAT)
+    @api_view(['GET'])
+    def view_func(request):
+        pass  # pragma: no cover
+
+    with pytest.raises(AssertionError) as excinfo:
+        generate_schema('/x/', view_function=view_func)
+    assert "Incompatible AutoSchema" in str(excinfo.value)