make jump_to go to right position in a sequence.

common/lib/xmodule/xmodule/modulestore/search.py

@@ -26,7 +26,7 @@ def path_to_location(modulestore, course_id, location):
     A location may be accessible via many paths. This method may
     return any valid path.
 
-    If the section is a sequence, position will be the position
+    If the section is a sequential or vertical, position will be the position
     of this location in that sequence.  Otherwise, position will
     be None. TODO (vshnayder): Not true yet.
     '''
@@ -83,15 +83,21 @@ def path_to_location(modulestore, course_id, location):
 
     path = find_path_to_course()
     if path is None:
-        raise(NoPathToItem(location))
+        raise NoPathToItem(location)
 
     n = len(path)
     course_id = CourseDescriptor.location_to_id(path[0])
     # pull out the location names
     chapter = path[1].name if n > 1 else None
     section = path[2].name if n > 2 else None
-
-    # TODO (vshnayder): not handling position at all yet...
+    # Figure out the position
     position = None
+    if n > 3:
+        section_desc = modulestore.get_instance(course_id, path[2])
+        child_locs = [c.location for c in section_desc.get_children()]
+        # positions are 1-indexed, and should be strings to be consistent with
+        # url parsing.
+        position = str(child_locs.index(path[3]) + 1)
+
 
     return (course_id, chapter, section, position)