last_submission_time for merged datasets at the forms endpoint

onadata/apps/api/tests/viewsets/test_merged_xform_viewset.py

@@ -50,6 +50,7 @@ def _create_merged_dataset(self, geo=False):
         view = MergedXFormViewSet.as_view({
             'post': 'create',
         })
+        # pylint: disable=attribute-defined-outside-init
         self.project = get_user_default_project(self.user)
         xform1 = self._publish_md(MD, self.user, id_string='a')
         xform2 = self._publish_md(MD, self.user, id_string='b')
@@ -224,6 +225,9 @@ def test_merged_datasets_data(self):
         detail_view = MergedXFormViewSet.as_view({
             'get': 'retrieve',
         })
+        xform_detail_view = XFormViewSet.as_view({
+            'get': 'retrieve',
+        })
 
         response = view(request, pk=merged_dataset['id'])
         self.assertEqual(response.status_code, 200)
@@ -264,7 +268,7 @@ def test_merged_datasets_data(self):
         expected_fruit = ['orange', 'mango']
         self.assertEqual(fruit, expected_fruit)
 
-        # check num_of_submissions
+        # check num_of_submissions /merged-datasets/[pk]
         response = detail_view(request, pk=merged_dataset['id'])
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.data['num_of_submissions'], 2)
@@ -273,6 +277,15 @@ def test_merged_datasets_data(self):
         self.assertEqual(response.data['last_submission_time'],
                          last_submission.date_created)
 
+        # check num_of_submissions /forms/[pk]
+        response = xform_detail_view(request, pk=merged_dataset['id'])
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(response.data['num_of_submissions'], 2)
+
+        # check last_submission_time
+        self.assertEqual(response.data['last_submission_time'],
+                         last_submission.date_created)
+
     def test_md_data_viewset(self):
         """Test retrieving data of a merged dataset at the /data endpoint"""
         merged_dataset = self._create_merged_dataset()

onadata/libs/serializers/xform_serializer.py

@@ -177,6 +177,26 @@ def get_num_of_submissions(self, obj):
             cache.set(key, count)
             return count
 
+    def get_last_submission_time(self, obj):
+        """Return datetime of last submission
+
+        If a form is a merged dataset then it is picked from the list of forms
+        attached to that merged dataset.
+        """
+        if 'last_submission_time' not in self.fields:
+            return None
+
+        if obj.is_merged_dataset:
+            values = [
+                x.last_submission_time
+                for x in obj.mergedxform.xforms.only('last_submission_time')
+                if x.last_submission_time
+            ]
+            if values:
+                return sorted(values, reverse=True)[0]
+
+        return obj.last_submission_time
+
 
 class XFormBaseSerializer(XFormMixin, serializers.HyperlinkedModelSerializer):
     formid = serializers.ReadOnlyField(source='id')
@@ -202,6 +222,7 @@ class XFormBaseSerializer(XFormMixin, serializers.HyperlinkedModelSerializer):
     enketo_url = serializers.SerializerMethodField()
     enketo_preview_url = serializers.SerializerMethodField()
     num_of_submissions = serializers.SerializerMethodField()
+    last_submission_time = serializers.SerializerMethodField()
     data_views = serializers.SerializerMethodField()
 
     class Meta:
@@ -239,6 +260,7 @@ class XFormSerializer(XFormMixin, serializers.HyperlinkedModelSerializer):
     enketo_url = serializers.SerializerMethodField()
     enketo_preview_url = serializers.SerializerMethodField()
     num_of_submissions = serializers.SerializerMethodField()
+    last_submission_time = serializers.SerializerMethodField()
     form_versions = serializers.SerializerMethodField()
     data_views = serializers.SerializerMethodField()