Increase configurability of bulk refresh parameter

The Elasticsearch bulk APIs support a configurable 'refresh' parameter
that can be set to:

1. empty string / true : perform refresh after operation completes
2. 'wait_for': wait until next scheduled refresh
3. false (default): don't do any refresh

See documentation at:

https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-refresh.html

Currently the `Document.update()` API accepts a `refresh` parameter
that, if `True`, passes `True` to the ES bulk API. There isn't currently
a way to pass 'wait_for'.

This commit modifies how `Document.update()` works so that it is
possible to pass `refresh='wait_for'`. I've implemented this in a
generic way, as opposed to hardcoding logic for 'wait_for', to support
future changes to this ES bulk API.

Note that, in keeping with the current convention, if
`refresh='wait_for'` is passed, this will override the value of
auto_refresh set either via setting or via the Document class. This
gives developers the maximum configurability here.

Author: chosak

django_elasticsearch_dsl/documents.py

@@ -191,10 +191,10 @@ def update(self, thing, refresh=None, action='index', parallel=False, **kwargs):
         """
         Update each document in ES for a model, iterable of models or queryset
         """
-        if refresh is True or (
-            refresh is None and self.django.auto_refresh
-        ):
+        if refresh is None and self.django.auto_refresh:
             kwargs['refresh'] = True
+        elif refresh is not None:
+            kwargs['refresh'] = refresh
 
         if isinstance(thing, models.Model):
             object_list = [thing]

tests/test_documents.py

@@ -268,6 +268,26 @@ def test_model_instance_update_no_refresh(self):
             doc.update(car)
             self.assertNotIn('refresh', mock.call_args_list[0][1])
 
+    def test_model_instance_update_refresh_wait_for(self):
+        doc = CarDocument()
+        doc.django.auto_refresh = False
+        car = Car()
+        with patch('django_elasticsearch_dsl.documents.bulk') as mock:
+            doc.update(car, refresh='wait_for')
+            self.assertEqual(
+                mock.call_args_list[0][1]['refresh'], 'wait_for'
+            )
+
+    def test_model_instance_update_refresh_wait_for_overrides_auto_refresh(self):
+        doc = CarDocument()
+        doc.django.auto_refresh = True
+        car = Car()
+        with patch('django_elasticsearch_dsl.documents.bulk') as mock:
+            doc.update(car, refresh='wait_for')
+            self.assertEqual(
+                mock.call_args_list[0][1]['refresh'], 'wait_for'
+            )
+
     def test_model_instance_iterable_update_with_pagination(self):
         class CarDocument2(DocType):
             class Django: