Make sure that all tab types used by the default for the course.tabs field work correctly

lms/djangoapps/courseware/tabs.py

@@ -91,6 +91,13 @@ def _discussion(tab, user, course, active_page):
     return []
 
 
+def _external_discussion(tab, user, course, active_page):
+    """
+    This returns a tab that links to an external discussion service
+    """
+    return [CourseTab('Discussion', tab['link'], active_page == 'discussion')]
+
+
 def _external_link(tab, user, course, active_page):
     # external links are never active
     return [CourseTab(tab['name'], tab['link'], False)]
@@ -150,6 +157,12 @@ def _staff_grading(tab, user, course, active_page):
     return []
 
 
+def _syllabus(tab, user, course, active_page):
+    """Display the syllabus tab"""
+    link = reverse('syllabus', args=[course.id])
+    return [CourseTab('Syllabus', link, active_page == 'syllabus')]
+
+
 def _peer_grading(tab, user, course, active_page):
 
     if user.is_authenticated():
@@ -216,6 +229,7 @@ VALID_TAB_TYPES = {
     'course_info': TabImpl(need_name, _course_info),
     'wiki': TabImpl(need_name, _wiki),
     'discussion': TabImpl(need_name, _discussion),
+    'external_discussion': TabImpl(key_checker(['link']), _external_discussion),
     'external_link': TabImpl(key_checker(['name', 'link']), _external_link),
     'textbooks': TabImpl(null_validator, _textbooks),
     'pdf_textbooks': TabImpl(null_validator, _pdf_textbooks),
@@ -225,7 +239,8 @@ VALID_TAB_TYPES = {
     'peer_grading': TabImpl(null_validator, _peer_grading),
     'staff_grading': TabImpl(null_validator, _staff_grading),
     'open_ended': TabImpl(null_validator, _combined_open_ended_grading),
-    'notes': TabImpl(null_validator, _notes_tab)
+    'notes': TabImpl(null_validator, _notes_tab),
+    'syllabus': TabImpl(null_validator, _syllabus)
     }