When putting an experiment live, ensure that any unpublished alternative pages have their latest draft revisions copied to the live table

The live table is not routinely updated while the page is in draft, so this step ensures that the version shown is an up-to-date one.

Author: gasman

experiments/models.py

@@ -48,6 +48,25 @@ class Experiment(ClusterableModel):
         FieldPanel('status'),
     ]
 
+    def __init__(self, *args, **kwargs):
+        super(Experiment, self).__init__(*args, **kwargs)
+        self._initial_status = self.status
+
+    def save(self, *args, **kwargs):
+        result = super(Experiment, self).save(*args, **kwargs)
+        if self._initial_status == 'draft' and self.status == 'live':
+            # For any alternative pages that are unpublished, copy the latest draft revision
+            # to the main table (with is_live=False) so that the revision shown as an alternative
+            # is not an out-of-date one
+            for alternative in self.alternatives.select_related('page'):
+                if not alternative.page.live:
+                    revision = alternative.page.get_latest_revision_as_page()
+                    revision.live = False
+                    revision.has_unpublished_changes = True
+                    revision.save()
+
+        return result
+
     def get_variations(self):
         return [self.control_page] + [alt.page for alt in self.alternatives.select_related('page')]