Remove label from forum posts by global staff

The motivation for this change is performance. The forums UI code gets
the list of users for each role and renders the staff label based on
those lists. The list for the staff role is expensive to compute because
there is no index on the is_staff attribute, and we cannot create one
because the User model is built into django.

Users with is_staff=True are still assigned the Moderator role upon
enrolling in a course, so this change will have no practical effect
except that a user who is granted staff privileges after enrolling in a
course will have to be made a Moderator in order for their posts to be
labeled.

Additionally, the UI did not use the list of users with the Student
role, so that list has been removed as well.

CHANGELOG.rst

@@ -5,6 +5,9 @@ These are notable changes in edx-platform.  This is a rolling list of changes,
 in roughly chronological order, most recent first.  Add your entries at or near
 the top.  Include a label indicating the component affected.
 
+LMS: Users with is_staff=True no longer have the STAFF label appear on
+their forum posts.
+
 Blades: Video start and end times now function the same for both YouTube and
 HTML5 videos. If end time is set, the video can still play until the end, after
 it pauses on the end time.

common/static/coffee/src/discussion/utils.coffee

@@ -26,7 +26,7 @@ class @DiscussionUtil
     @loadFlagModerator($("#discussion-container").data("flag-moderator"))
 
   @isStaff: (user_id) ->
-    staff = _.union(@roleIds['Staff'], @roleIds['Moderator'], @roleIds['Administrator'])
+    staff = _.union(@roleIds['Moderator'], @roleIds['Administrator'])
     _.include(staff, parseInt(user_id))
 
   @isTA: (user_id) ->

lms/djangoapps/django_comment_client/tests/test_utils.py

@@ -39,6 +39,7 @@ class AccessUtilsTestCase(TestCase):
         self.course_id = 'edX/toy/2012_Fall'
         self.student_role = RoleFactory(name='Student', course_id=self.course_id)
         self.moderator_role = RoleFactory(name='Moderator', course_id=self.course_id)
+        self.community_ta_role = RoleFactory(name='Community TA', course_id=self.course_id)
         self.student1 = UserFactory(username='student', email='student@edx.org')
         self.student1_enrollment = CourseEnrollmentFactory(user=self.student1)
         self.student_role.users.add(self.student1)
@@ -47,10 +48,14 @@ class AccessUtilsTestCase(TestCase):
         self.moderator = UserFactory(username='moderator', email='staff@edx.org', is_staff=True)
         self.moderator_enrollment = CourseEnrollmentFactory(user=self.moderator)
         self.moderator_role.users.add(self.moderator)
+        self.community_ta1 = UserFactory(username='community_ta1', email='community_ta1@edx.org')
+        self.community_ta_role.users.add(self.community_ta1)
+        self.community_ta2 = UserFactory(username='community_ta2', email='community_ta2@edx.org')
+        self.community_ta_role.users.add(self.community_ta2)
 
     def test_get_role_ids(self):
         ret = utils.get_role_ids(self.course_id)
-        expected = {u'Moderator': [3], u'Student': [1, 2], 'Staff': [3]}
+        expected = {u'Moderator': [3], u'Community TA': [4, 5]}
         self.assertEqual(ret, expected)
 
     def test_has_forum_access(self):

lms/djangoapps/django_comment_client/utils.py

@@ -9,7 +9,7 @@ from django.core.urlresolvers import reverse
 from django.db import connection
 from django.http import HttpResponse
 from django.utils import simplejson
-from django_comment_common.models import Role
+from django_comment_common.models import Role, FORUM_ROLE_STUDENT
 from django_comment_client.permissions import check_permissions_by_view
 
 import mitxmako
@@ -42,12 +42,8 @@ def merge_dict(dic1, dic2):
 
 
 def get_role_ids(course_id):
-    roles = Role.objects.filter(course_id=course_id)
-    staff = list(User.objects.filter(is_staff=True).values_list('id', flat=True))
-    roles_with_ids = {'Staff': staff}
-    for role in roles:
-        roles_with_ids[role.name] = list(role.users.values_list('id', flat=True))
-    return roles_with_ids
+    roles = Role.objects.filter(course_id=course_id).exclude(name=FORUM_ROLE_STUDENT)
+    return dict([(role.name, list(role.users.values_list('id', flat=True))) for role in roles])
 
 
 def has_forum_access(uname, course_id, rolename):