From cd49e1bb686f747969d13e875111f448cf5b71bb Mon Sep 17 00:00:00 2001
From: Vik Paruchuri <vik@edx.org>
Date: Thu, 13 Jun 2013 16:00:28 -0400
Subject: [PATCH] Check to see if a location is valid before displaying it for
 instructor grading

---
 .../open_ended_grading/staff_grading_service.py  | 11 ++++++++++-
 lms/djangoapps/open_ended_grading/utils.py       | 16 ++++++++++++++++
 lms/djangoapps/open_ended_grading/views.py       |  2 +-
 3 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 lms/djangoapps/open_ended_grading/utils.py

diff --git a/lms/djangoapps/open_ended_grading/staff_grading_service.py b/lms/djangoapps/open_ended_grading/staff_grading_service.py
index 2c611b4481..a2d905be0b 100644
--- a/lms/djangoapps/open_ended_grading/staff_grading_service.py
+++ b/lms/djangoapps/open_ended_grading/staff_grading_service.py
@@ -15,6 +15,7 @@ from xmodule.course_module import CourseDescriptor
 from student.models import unique_id_for_user
 from xmodule.x_module import ModuleSystem
 from mitxmako.shortcuts import render_to_string
+from utils import does_location_exist
 
 log = logging.getLogger(__name__)
 
@@ -240,7 +241,6 @@ def get_next(request, course_id):
     return HttpResponse(_get_next(course_id, grader_id, location),
                         mimetype="application/json")
 
-
 def get_problem_list(request, course_id):
     """
     Get all the problems for the given course id
@@ -266,6 +266,15 @@ def get_problem_list(request, course_id):
     _check_access(request.user, course_id)
     try:
         response = staff_grading_service().get_problem_list(course_id, unique_id_for_user(request.user))
+        response = json.loads(response)
+        problem_list = response['problem_list']
+        valid_problem_list = []
+        for i in xrange(0,len(problem_list)):
+            if does_location_exist(course_id, problem_list[i]['location']):
+                valid_problem_list.append(problem_list[i])
+        response['problem_list'] = valid_problem_list
+        response = json.dumps(response)
+
         return HttpResponse(response,
                             mimetype="application/json")
     except GradingServiceError:
diff --git a/lms/djangoapps/open_ended_grading/utils.py b/lms/djangoapps/open_ended_grading/utils.py
new file mode 100644
index 0000000000..7634977397
--- /dev/null
+++ b/lms/djangoapps/open_ended_grading/utils.py
@@ -0,0 +1,16 @@
+from xmodule.modulestore import search
+from xmodule.modulestore.django import modulestore
+from xmodule.modulestore.exceptions import ItemNotFoundError
+
+def does_location_exist(course_id, location):
+    """
+    Checks to see if a valid module exists at a given location (ie has not been deleted)
+    course_id - string course id
+    location - string location
+    """
+    try:
+        search.path_to_location(modulestore(), course_id, location)
+        return True
+    except ItemNotFoundError:
+        #If the problem cannot be found at the location received from the grading controller server, it has been deleted by the course author.
+        return False
diff --git a/lms/djangoapps/open_ended_grading/views.py b/lms/djangoapps/open_ended_grading/views.py
index a914e434a9..797c90f9a4 100644
--- a/lms/djangoapps/open_ended_grading/views.py
+++ b/lms/djangoapps/open_ended_grading/views.py
@@ -179,6 +179,7 @@ def student_problem_list(request, course_id):
     error_text = ""
     problem_list = []
     base_course_url = reverse('courses')
+    list_to_remove = []
 
     try:
         #Get list of all open ended problems that the grading server knows about
@@ -192,7 +193,6 @@ def student_problem_list(request, course_id):
             problem_list = problem_list_dict['problem_list']
 
         #A list of problems to remove (problems that can't be found in the course)
-        list_to_remove = []
         for i in xrange(0, len(problem_list)):
             try:
                 #Try to load each problem in the courseware to get links to them