fix preview draft link. We need to generate the link target url directly rather…

fix preview draft link. We need to generate the link target url directly rather than using jump_to. I think jump_to is not properly finding the draft objects and needs more investigation

cms/djangoapps/contentstore/views.py

@@ -272,6 +272,26 @@ def edit_unit(request, location):
     containing_section_locs = modulestore().get_parent_locations(containing_subsection.location)
     containing_section = modulestore().get_item(containing_section_locs[0])
 
+    # cdodge hack. We're having trouble previewing drafts via jump_to redirect
+    # so let's generate the link url here 
+
+    # need to figure out where this item is in the list of children as the preview will need this
+    index =1
+    for child in containing_subsection.get_children():
+        if child.location == item.location:
+            break
+        index = index + 1
+
+    preview_lms_link = '//{preview}{lms_base}/courses/{org}/{course}/{course_name}/courseware/{section}/{subsection}/{index}'.format(
+            preview='preview.',
+            lms_base=settings.LMS_BASE,            
+            org=course.location.org,
+            course=course.location.course, 
+            course_name=course.location.name, 
+            section=containing_section.location.name, 
+            subsection=containing_subsection.location.name, 
+            index=index)
+
     unit_state = compute_unit_state(item)
 
     try: