Set action for HEAD requests (#7223)

* Test viewset action attr

* Add 'head' to viewset actions map

rest_framework/viewsets.py

@@ -93,6 +93,10 @@ class ViewSetMixin:
 
         def view(request, *args, **kwargs):
             self = cls(**initkwargs)
+
+            if 'get' in actions and 'head' not in actions:
+                actions['head'] = actions['get']
+
             # We also store the mapping of request methods to actions,
             # so that we can later set the action attribute.
             # eg. `self.action = 'list'` on an incoming GET request.
@@ -104,9 +108,6 @@ class ViewSetMixin:
                 handler = getattr(self, action)
                 setattr(self, method, handler)
 
-            if hasattr(self, 'get') and not hasattr(self, 'head'):
-                self.head = self.get
-
             self.request = request
             self.args = args
             self.kwargs = kwargs

tests/test_viewsets.py

@@ -37,14 +37,18 @@ class ActionViewSet(GenericViewSet):
     queryset = Action.objects.all()
 
     def list(self, request, *args, **kwargs):
-        return Response()
+        response = Response()
+        response.view = self
+        return response
 
     def retrieve(self, request, *args, **kwargs):
         return Response()
 
     @action(detail=False)
     def list_action(self, request, *args, **kwargs):
-        raise NotImplementedError
+        response = Response()
+        response.view = self
+        return response
 
     @action(detail=False, url_name='list-custom')
     def custom_list_action(self, request, *args, **kwargs):
@@ -155,6 +159,22 @@ class InitializeViewSetsTestCase(TestCase):
             self.assertNotIn(attribute, dir(bare_view))
             self.assertIn(attribute, dir(view))
 
+    def test_viewset_action_attr(self):
+        view = ActionViewSet.as_view(actions={'get': 'list'})
+
+        get = view(factory.get('/'))
+        head = view(factory.head('/'))
+        assert get.view.action == 'list'
+        assert head.view.action == 'list'
+
+    def test_viewset_action_attr_for_extra_action(self):
+        view = ActionViewSet.as_view(actions=dict(ActionViewSet.list_action.mapping))
+
+        get = view(factory.get('/'))
+        head = view(factory.head('/'))
+        assert get.view.action == 'list_action'
+        assert head.view.action == 'list_action'
+
 
 class GetExtraActionsTests(TestCase):