prevent pagination on error responses. #277

although it is a deviation from the main behaviour,
paginating error responses makes little sense in
virtually all realistic scenarios.

drf_spectacular/openapi.py

@@ -1027,6 +1027,8 @@ def _get_response_for_code(self, serializer, status_code, media_types=None):
         elif isinstance(serializer, dict):
             # bypass processing and use given schema directly
             schema = serializer
+            # prevent invalid dict case in _is_list_view() as this not a status_code dict.
+            serializer = None
         else:
             warn(
                 f'could not resolve "{serializer}" for {self.method} {self.path}. Expected either '
@@ -1036,7 +1038,11 @@ def _get_response_for_code(self, serializer, status_code, media_types=None):
             schema = build_basic_type(OpenApiTypes.OBJECT)
             schema['description'] = _('Unspecified response body')
 
-        if self._is_list_view(serializer) and not get_override(serializer, 'many') is False:
+        if (
+            self._is_list_view(serializer)
+            and get_override(serializer, 'many') is not False
+            and '200' <= status_code < '300'
+        ):
             schema = build_array_type(schema)
             paginator = self._get_paginator()
 

tests/test_regressions.py

@@ -1721,3 +1721,28 @@ def view_func(request, format=None):
 
     schema = generate_schema('/api/v1/x/', view_function=view_func)
     assert '/x/' in schema['paths']
+
+
+def test_list_and_pagination_on_non_2XX_schemas(no_warnings):
+    @extend_schema_view(
+        list=extend_schema(responses={
+            200: SimpleSerializer,
+            400: {'type': 'object', 'properties': {'code': {'type': 'string'}}},
+            403: OpenApiTypes.OBJECT
+        })
+    )
+    class XViewset(mixins.ListModelMixin, viewsets.GenericViewSet):
+        serializer_class = SimpleSerializer
+        queryset = SimpleModel.objects.none()
+        pagination_class = pagination.LimitOffsetPagination
+
+    schema = generate_schema('x', XViewset)
+    assert get_response_schema(schema['paths']['/x/']['get']) == {
+        '$ref': '#/components/schemas/PaginatedSimpleList'
+    }
+    assert get_response_schema(schema['paths']['/x/']['get'], '400') == {
+        'type': 'object', 'properties': {'code': {'type': 'string'}}
+    }
+    assert get_response_schema(schema['paths']['/x/']['get'], '403') == {
+        'type': 'object', 'additionalProperties': {}
+    }