Ensure that viewset actions may be identified as list views

is_list_view only checks to see whether the view action is 'list'.

This means you cannot define an action with `detail=False` that will
generate a schema with a list response.

This commit allows specifying 'many=True' on an action to achieve this

rest_framework/schemas/utils.py

@@ -15,7 +15,7 @@ def is_list_view(path, method, view):
     """
     if hasattr(view, 'action'):
         # Viewsets have an explicitly defined action, which we can inspect.
-        return view.action == 'list'
+        return view.action == 'list' or view.many
 
     if method.lower() != 'get':
         return False

rest_framework/viewsets.py

@@ -75,6 +75,9 @@ class ViewSetMixin:
         # The detail initkwarg is reserved for introspecting the viewset type.
         cls.detail = None
 
+        # The many initkwarg is reserved for introspecting the viewset return type.
+        cls.many = None
+
         # Setting a basename allows a view to reverse its action urls. This
         # value is provided by the router through the initkwargs.
         cls.basename = None

tests/schemas/test_openapi.py

@@ -10,6 +10,7 @@ from django.utils.translation import gettext_lazy as _
 from rest_framework import filters, generics, pagination, routers, serializers
 from rest_framework.authtoken.views import obtain_auth_token
 from rest_framework.compat import uritemplate
+from rest_framework.decorators import action
 from rest_framework.parsers import JSONParser, MultiPartParser
 from rest_framework.renderers import (
     BaseRenderer, BrowsableAPIRenderer, JSONOpenAPIRenderer, JSONRenderer,
@@ -866,6 +867,22 @@ class TestOperationIntrospection(TestCase):
         assert schema['paths']['/account/{id}/']['patch']['operationId'] == 'partialUpdateExampleViewSet'
         assert schema['paths']['/account/{id}/']['delete']['operationId'] == 'destroyExampleViewSet'
 
+    def test_viewset_with_list_action(self):
+        router = routers.SimpleRouter()
+
+        class ViewSetWithAction(views.ExampleViewSet):
+            @action(detail=False, many=True)
+            def list_action(self, request, *args, **kwargs):
+                pass
+
+        router.register('account', ViewSetWithAction, basename="account")
+        urlpatterns = router.urls
+
+        generator = SchemaGenerator(patterns=urlpatterns)
+        request = create_request('/')
+        schema = generator.get_schema(request=request)
+        assert schema['paths']['/account/list_action/']['get']['responses']['200']['content']['application/json']['schema']['type'] == 'array'
+
     def test_serializer_datefield(self):
         path = '/'
         method = 'GET'